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  • 1.
    Ahlblad, Gustav
    KTH, Superseded Departments, Polymer Technology.
    Imaging chemiluminescence applied to oxidation of rubber materials and polyamide1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In this thesis the heterogeneous nature of thermal oxidationof polymer materials have been investigated by imagingchemiluminescence (KL). The issues of oxidation depth profilesand physical spreading of oxidation in rubbers materials andpolyamide have been addressed.

    For this purpose an ICL instrument was designed showing thefollowing unique features: high sensitivity - particularly highsignal to noise ratio for small samples, high spatialresolution and a high accuracy of the in-plane temperature.With these characteristics, the spatial distribution of the CLemission from various polymer materials can be obtained inoxygen and, which has not previously been reported, in nitrogenatmosphere.

    An experimental method was developed to estimate theoxidation depth in HTPB tubber duringin situoxidation. Thein situoxidation depth data were correlated to oxidation depthprofiles of pre-aged samples from measurements in nitrogenatmosphere. Oxidation depth profiles in nitrogen were alsodetermined for pre-aged PA 6,6 and correlated to carbonyl indexdepth profiles obtained by FlTR microscopy. By subjetting HTPBrubber samples to static as well as dynamit-mechanical load at100&degree;C different oxidation depth profiles could beidentified.

    Experiments on oxidation in populations of EPDM particlesdemonstrated the presence of two separate distributions ofinitiation times for the individual particles, suggesting twodifferent initiation mechanisms. Further experiments showed acorrelation of the initiation times of adjacent particles. Thecorrelation was improved in populations with closerinterparticle distances. The results were interpreted in termsof a physical spreading of the oxidation from particle toparticle. Results from GC-MS and TG measurements indicated thepresence of volatile species released on oxidation of theparticles.

    A mechanism is proposed for the physical spreading ofoxidation observed, involving infectious spreading in the gasphase from heterogeneously distributed initiation sites.

    Keywords:Imaging chemiluminescence, oxidation, depthprofiles, physical spreading, HTPB rubber, EPDM, PA 6,6.

  • 2.
    Albertsson, Ann-Christine
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Edlund, Ulrica
    KTH, Superseded Departments, Polymer Technology.
    Stridsberg, K.
    Controlled ring-opening polymerization of lactones and lactides2000In: Macromolecular Symposia, ISSN 1022-1360, E-ISSN 1521-3900, Vol. 157, 39-46 p.Article in journal (Refereed)
    Abstract [en]

    1,5-dioxepan-2-one (DXO) is presented as a versatile component in biodegradable polymers for biomedical applications. Copolymerization of DXO and L-lactide yielded a semi-crystalline, yet flexible, material where the extent of crystallinity and erosion characteristics were controlled by an appropriate choice of copolymer composition. Crosslinked PDXO was polymerized as a novel biodegradable elastomer. The degradation behavior of these materials were explored in vitro. Microspheres from poly(DXO-co-L-LA) were prepared and shown to be promising candidates for controlled release. The polymer composition and drug solubility provided effective means of controlling the drug delivery pattern.

  • 3.
    Albertsson, Ann-Christine
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Olander, Björn
    KTH, Superseded Departments, Polymer Technology.
    Edlund, Ulrica
    KTH, Superseded Departments, Polymer Technology.
    Källrot, Martina
    KTH, Superseded Departments, Polymer Technology.
    Increased biocompatibility by surface modification2004In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 228, U508-U508 p.Article in journal (Other (popular science, discussion, etc.))
  • 4.
    Albertsson, Ann-Christine
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Varma, I. K.
    Recent developments in ring opening polymerization of lactones for biomedical applications2003In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 4, no 6, 1466-1486 p.Article, review/survey (Refereed)
    Abstract [en]

    Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbabale devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of polyesters and tailoring the properties by proper control of molecular weight, composition, and architecture so as to meet the stringent requirements of devices in the medical field. The effect of structure on properties and degradation has been discussed. The applications of these polymers in the biomedical field are described in detail.

  • 5.
    Backman, Anna
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Lange, Jakob
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Transport properties of uniaxially oriented aliphatic polyketone2004In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 42, no 6, 947-955 p.Article in journal (Refereed)
    Abstract [en]

    The oxygen, carbon dioxide, and water-transport properties of a uniaxially oriented aliphatic polyketone were determined. The polyketone was drawn to 5-10 times its original length. The transport properties were related to changes in crystallinity estimated by differential scanning calorimetry and density measurements and by changes in the molecular and crystal orientation assessed by, respectively, infrared and X-ray spectroscopy. The film structures were characterized by confocal scanning laser microscopy and scanning electron microscopy. Stress-strain tests on the drawn specimens enabled the impacts of orientation on the transport and mechanical properties to be compared. A draw-induced increase in crystallinity and molecular orientation yielded permeabilities at a draw ratio of 10 that were 30-40% of the original value, and the percentage decrease was basically independent of the type of gas/vapor molecule. Also, the diffusivities of oxygen and carbon dioxide decreased by an order of magnitude. The fact that the amorphous permeability was peaking at a draw ratio of about 5 was a consequence of a peak in amorphous solubility, which was very high for oxygen and absent for water. It was suggested that the peak in solubility was mainly caused by the destruction of the polymer hydrogen-bond network during drawing and crystal reorientation. The impact of structural reorganization within the polymer and presence of surface valleys seemed to have less impact on the mechanical properties than on the transport properties. This suggested that transport data are more sensitive than mechanical data in probing material defects and changes in molecular packing and morphology.

  • 6.
    Bellander, Martin
    KTH, Superseded Departments, Polymer Technology.
    High pressure vulcanization: crosslinking of diene rubbers without vulcanization agents1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    High pressure vulcanization (HPV) is defined in this thesisas crosslinking of rubber materialsat elevated pressure andtemperature, without the use of any vulcanization agents. Thisis atotally new vulcanization technique, not used in theindustry today. The HPV technique,however, has an interestingpotential since no hazardous chemicals need to be handled,thematerial does not contain any additives. The phenomenon thatcertain rubber materials can be crosslinked in this way wasobserved already in the 1960s, but there has been a lack ofknowledge of the underlying reaction mechanisms, kinetics, theresulting network structure and also the correlation betweenthe molecular structure and the physical properties ofthesematerials. The purpose of this thesis is to increase theknowledge of high pressurevulcanization, with respect toreaction kinetics and mechanisms, network structure andphysical properties.

    A low cis-polybutadiene was used as a model material forcrosslinking at high pressure (10-290 MPa) and temperature(240-250°C), and comparisons were made withperoxidevulcanizates. Both unfilled and carbon black filledsamples were studied. Nitrile- and styrene-butadienerubber werealso crosslinked successfully. Crosslink density is a centralconcept inthis thesis and was evaluated by swellingmeasurements. The microstructural changesoccurring duringvulcanization were studied by Fourier Transform InfraredSpectroscopy(FTIR) and 13 C solid state nuclear magneticresonance (NMR). The mechanical propertieswere investigated bydynamic mechanical thermal analysis (DMTA), tensile testing,and permanent set and stress relaxation measurements.Theprogress of the reaction proved to be well controlled by thetreatment time, temperature and pressure, resulting inmaterials with widely different properties within onesinglecompound due to the possibility of controlling thecrosslink density during the vulcanizationprocess. The reactionmechanism was shown to be of a radical type, and vinylunsaturations inthe polybutadiene are consumed concurrentlywith the crosslink formation. The effect ofpressure on thereaction is a decrease in molecular mobility, which results inhighercrosslinking reaction rate due to a decrease intermination reactions. When a carbon black filleris introduced,the number of polymer-filler interactions is increased due tothe ability of thepolymer to penetrate the carbon blackstructure under pressure. The mechanical properties areas goodas those of peroxide vulcanizates, and especially theresistance to deformation inservice-use at elevatedtemperatures suggests that the resulting material may be usedin gasketand seal applications. In spite of the difficulties ofmould sealing that arise at elevatedpressures, it was possibleto obtain vulcanized samples by common injection mouldingwithproperties comparable to those obtained by traditionalvulcanization.

    Keywords:High Pressure Vulcanization, Vulcanization,Crosslinking, Pressure, Elevated Temperature, Polybutadiene,Carbon Black, Rubber-Carbon Black Interactions, CrosslinkDensity, Peroxide Vulcanization, Injection Moulding,Nitrile-Butadiene Rubber.

  • 7. Bexell, U.
    et al.
    Olsson, M.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Samuelsson, J.
    Sundell, P. E.
    A tribological study of a novel pre-treatment with linseed oil bonded to mercaptosilane treated aluminium2003In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 166, no 03-feb, 141-152 p.Article in journal (Refereed)
    Abstract [en]

    In sheet metal forming processes, lubricants are necessary in order to prevent galling, i.e. material transfer from the sheet metal to the tool surface and to control friction. Today, dry lubricants are increasingly being used for solving this problem. Among these, multifunctional coatings, often referred to as permanent coatings, normally based on organic resins, are lubricants which have the potential to increase the formability without additional lubrication, give corrosion protection, fingerprint and scratch resistance during handling and transport and finally, serve as a pre-treatment before painting. With increasing concern about the environment and human health it is important to develop new environmentally friendly pre-treatments in the surface engineering of metal substrates. This is mainly due to the toxic and carcinogenic properties of the chromium based surface pre-treatments frequently used in the industry. During the last decade, simple solution-dip silane based pre-treatments have emerged as promising candidates for the replacement of currently used pre-treatments of metals. A silane film can give good corrosion protection properties but is often too thin to prevent galling under a forming operation. A renewed interest for using vegetable oils in surface engineering has appeared lately due to several factors. Vegetable oils are renewable resources, modem technology can produce more well defined and pure oils, and the fatty acid content can be altered with modern crops development techniques. With the proper choice of silane pre-treatment of a metal surface, a vegetable oil can be coupled to the surface and give the desired lubrication properties. In this paper, aluminium sheets have been pre-treated with a mercapto silane after which a vegetable oil has been attached. The coupling between the silane and the oil was obtained through a photoinduced thiol-ene reaction using UV-radiation. The influence of different process parameters on the friction and wear behaviour was evaluated using modified scratch testing. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and contact angle measurements were used to characterise the as-deposited surface films and their tribological behaviour, i.e. failure mechanisms. The results obtained show that the unsaturated vegetable oil has reacted with the thiol groups via the thiol-ene reaction forming a surface film. Also, the results show that the thickness of the films is of importance for the tribological characteristics, i.e. a too thin layer (less than 25 A in the present work) results in high friction and severe adhesive wear. However, a thicker layer with enhanced load carrying capacity can be produced with a proper heat treatment of the deposited vegetable oil. Finally, the results show that thick (more than 200 Angstrom in the present work) silane films are sensitive to brittle fracture when exposed to a sliding contact.

  • 8.
    Björk, Folke.
    et al.
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Eriksson, C. A.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Khabbaz, F.
    Degradation of components in flooring systems in humid and alkaline environments2003In: Construction and Building Materials, ISSN 0950-0618, E-ISSN 1879-0526, Vol. 17, no 3, 213-221 p.Article in journal (Refereed)
    Abstract [en]

    Constituents from products that are used in the flooring on a concrete slab such as carpets of plasticised PVC and water-based adhesives sometimes degrade in an alkaline and humid environment. The concrete itself could be such an environment. In order to examine the effect of different levels of alkalinity and humidity on the mentioned products a specialised procedure was developed. By this procedure it was possible to imitate the effect of an environment of alkalinity and humidity corresponding to a recently produced concrete slab on different substances and also collect volatile degradation products produced. Degradation of some of the constituents was dependent on the levels of alkalinity and humidity, although there were significant differences in the possibility to resist the environmental factors. For some of the components, an increase in alkalinity resulted in a much higher production of degradation products even when the relative humidity was kept on a comparatively low level. The results give basis for a recommendation not to adhere plastic floorings directly to a recently produced slab of high-quality concrete because the alkaline material in the concrete could cause degradation.

  • 9.
    Bruhm, Johnny
    KTH, Superseded Departments, Polymer Technology.
    Harmetal powder injection moulding (PIM): process development2002Licentiate thesis, comprehensive summary (Other scientific)
  • 10. Brunius, C. F.
    et al.
    Edlund, Ulrica
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Synthesis and in vitro degradation of poly(N-vinyl-2-pyrrolidone)-based graft copolymers for biomedical applications2002In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 40, no 21, 3652-3661 p.Article in journal (Refereed)
    Abstract [en]

    This work is devoted to the design of a novel family of hydrosoluble biomaterials: poly(N-vinyl-2-pyrrolidone) (PVP)-based graft copolymers. A synthesis route has been elaborated in which omega-functionalized PVP is prepared via chain-transfer radical polymerization, end-group modified, and subsequently grafted onto a polyhydroxylated backbone, typically dextran or poly(vinyl alcohol). The resulting graft copolymer biomaterials are designed for use in various biomedical applications, particularly as materials with a stronger potential for plasma expansion than already existing products have. The graft copolymers are potentially degradable because the PVP grafts are connected to the polyol backbone via a hydrolytically labile carbonate or ester linkage. The degradation of the graft copolymers was performed in vitro over a period of 6 weeks.

  • 11. Busson, P.
    et al.
    Ortegren, J.
    Ihre, H.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Andersson, G.
    Ferroelectric liquid crystalline dendrimers: Synthesis, thermal behavior, and electrooptical characterization2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 5, 1221-1229 p.Article in journal (Refereed)
    Abstract [en]

    The preparation and characterization of a series of novel ferroelectric liquid crystalline dendrimers are presented. End-capping of 1-, 2-, and 3-generation dendrimers based on 2,2-bis(hydroxymethyl)propionic acid with mesogens gave surface-functionalized liquid crystalline compounds with 6, 12, and 24 mesogen-containing units, respectively. 4 -((R)-1-Methylheptyloxy)phenyl 4-(4 '-[10(hydroxycarbonyl)decyloxyl phenyl)benzoate was synthesized and used as a mesogen-containing unit. The purity and structure of each compound were determined by H-1 NMR spectroscopy, size exclusion chromatography, and elemental analysis. Differential scanning calorimetry and optical microscopy were used to investigate the mesomorphic properties of the mesogen-functionalized dendrimers. The materials displayed a variety of mesophases, including the smectic C* phase. All the liquid crystalline dendrimers showed ferroelectricity, and tilt angle and spontaneous polarization measurements were performed. The obtained results show that the ferroelectric properties of the materials are independent of the generation number of the dendritic scaffold.

  • 12. Busson, P.
    et al.
    Ortegren, J.
    Ihre, H.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Andersson, G.
    Eriksson, A.
    Lindgren, M.
    Preparation of mesogen-functionalized dendrimers for second-order nonlinear optics2002In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 35, no 5, 1663-1671 p.Article in journal (Refereed)
    Abstract [en]

    Liquid crystalline dendrimers with peripheral mesogen-containing units have been prepared. Multistep synthesis with several selective reactions was used in the preparation of the mesogen-containing molecules, 4-[10-(hydroxycarbonyl)decyloxy]phenyl 4-[4'-(2-(R)-octyloxy)-3'-nitrophenyl]benzo ate and 4-[10-(hydroxycarbonyl)decyloxy]biphenyl 4-[4'-(2-(R)-octyloxy)-3'-nitrophenyl]benzoate. Both molecules possessed an electron-accepting nitro group placed perpendicular to the long axis of the molecules in order to enhance the nonlinear optical activity. A second generation hydroxyl functional aliphatic dendrimer based on the dihydroxy acid, 2,2-bis(hydroxymethyl)propionic acid, was used as dendritic scaffold and was subsequently functionalized with the aforementioned groups. The purity and structure of the two liquid crystalline dendrimers were determined by H-1 NMR spectroscopy, size exclusion chromatography, and elemental analysis. The synthesis of both the mesogen-containing units and the liquid crystalline dendrimers is described in detail. Investigation of the liquid crystalline properties of the materials by differential scanning calorimetry and optical microscopy showed that they exhibited different mesophases, including the chiral smectic C phase. Ferroelectric switching was observed in this tilted phase, and electrooptical properties, including tilt angle and spontaneous polarization measurements, were investigated. Finally, the nonlinear optical properties of one of the materials were preliminary characterized.

  • 13.
    Busson, Philippe
    KTH, Superseded Departments, Polymer Technology.
    Monomiric and dendritic liquid crystalline materials2000Doctoral thesis, comprehensive summary (Other scientific)
  • 14. Camacho, W.
    et al.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Near infrared (NIR) spectroscopy compared with thermogravimetric analysis as a tool for on-line prediction of water diffusion in polyamide 6,62002In: Polymer international, ISSN 0959-8103, E-ISSN 1097-0126, Vol. 51, no 12, 1366-1370 p.Article in journal (Refereed)
    Abstract [en]

    NIR spectroscopy in the transmission mode and thermogravimetric analysis were used to predict diffusion of water into polyamide 6,6 samples immersed in water at 40, 60, 75 and 90degreesC for different periods of time. The sorption curves between 40 and 75 were sigmoidal indicating that the surface concentration was time dependent. The sorption curves were readily fitted by the use of a time-dependent surface concentration and a water-concentration-dependent diffusivity. The zero-concentration water diffusivity decreased non-linearly and the activation energy of diffusion increased from 24 to 58 kJ mol(-1), with decreasing temperature. The surface concentration relaxation time decreased rapidly. The sorption of water in thick polyamide samples was readily characterized by FT-NIR spectroscopy. The accuracy and feasibility of this method was similar to conventional thermogravimetric methods. The greatest advantage of FT-NIR, however, is the possibility of detecting and monitoring the moisture concentration on-line and in a non-destructive way.

  • 15. Camacho, W.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Assessment of thermal and thermo-oxidative stability of multiextruded recycled PP, HDPE and a blend thereof2002In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 78, no 2, 385-391 p.Article in journal (Refereed)
    Abstract [en]

    Differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA) and chemiluminescence (CL) techniques have been used for assessment of thermal and thermo-oxidative stability of recycled PP, HDPE and their blend containing 20 wt.% of PP. The pure polymers and the blend were subjected to six extrusion cycles. The oxidation induction time (OIT) of the PP, PE and the blend decreased with the number of extrusion cycles also did the temperature of oxidation (T-ox). The thermal stability of PE decreased with the number of number of processing cycles, which may indicate that the shear forces during processing induce chain scission of the polymer backbone leading mainly to shortening of the chains. PP, however showed a decrease in thermal stability up to the third extrusion, and about the same stability during further processing. Thus chain scission predominated during all the extrusions and no chain branching or crosslinking were observed. The behaviour of the blend showed a synergetic tendency and did not obey the mixture rule. The CL runs produced a clearer picture of the oxidation process in blends since two peaks were observed, a sharp one corresponding to the PP and the other of bimodal shape to PE. The PP appeared to oxidize first and accelerated the oxidation of PE due to the presence of oxidation sites in the PE-PP interfaces. The blend of PP an HDPE mechanically mixed appeared to be a two-phase system in the molten state. This information can not be obtained from DSC and TG experiments.

  • 16. Camacho, W.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    NIR, DSC, and FTIR as quantitative methods for compositional analysis of blends of polymers obtained from recycled mixed plastic waste2001In: Polymer Engineering and Science, ISSN 0032-3888, E-ISSN 1548-2634, Vol. 41, no 9, 1626-1635 p.Article in journal (Refereed)
    Abstract [en]

    Methods for the determination of the composition of two binary blends in mixtures of recycled polymeric materials were analyzed and compared. Recycled polypropylene/polyethylene (PP/HDPE) and recycled poly(acryl-butadiene-styrene) and polypropylene(ABS/PP) were used to develop and validate the methods. Diffuse reflectance near infrared spectroscopy (NIRS) offers high sensitivity and ease of operation and a possibility to perform multivariate data analysis. In comparison, differential scanning calorimetry (DSC) and Mid-IR which are commonly used for this purpose require certain sample preparation and are indeed time consuming. In addition, the low sensitivity of these two methods to concentrations lower than 1% wt makes their application in quality control of recycled polymers inappropriate. NIR can be used for estimating the composition of the recyclate on-line in only a few seconds, no sample preparation is required, and high precision is achieved. We obtained a root mean square error of prediction (RMSEP) equal to 0.21% wt in the interval from 0-15% wt of PP in HDPE and a RMSEP equal to 0.91% wt in the interval 0-100%. For blends of PP/ABS a RMSEP of 0.74% wt in the range 0-100% and 0.32% wt in the range 0-15% wt PP was calculated. Most of the variation in the spectral data with respect to the polymer blend composition for all the studied blends were explained by two principal components (PC). The optimal number of factors (PC) was determined by cross-validation analysis.

  • 17. Camacho, W.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Quality-determination of recycled plastic packaging waste by identification of contaminants by CC-MS after microwave assisted extraction (MAE)2000In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 71, no 1, 123-134 p.Article in journal (Refereed)
    Abstract [en]

    The quality of recycled resins of high density polyethylene (HDPE) and polypropylene (PP) separated from mixed solid waste (MSW) were studied by analyzing the tentative low molecular weight contaminants. For that purpose a microwave assisted extraction (MAE) technique was developed using MDPE and two aromatic antioxidants (Irganox 1010 and Irgafos 168) as models. A 50:50 mixture of cyclohexane and isopropanol gave high recovery yields; 97% for Irgafos 168 and 93% for Irganox 1010 and short extraction times. Limonene, isopropylester of myristic and palmitic acids were examples of products identified in recycled HDPE. These compounds are typically fragrance and flavor constituents. In addition alcohols, esters, ketones were identified. Most of the substances are constituents of the packaging fillings at their first usage. But the possibility that contaminants may have entered the material by contact with other plastics is not excluded. The major category of compounds identified already in the virgin material is composed of aliphatic hydrocarbons (e.g. pentadecane, hexadecaned, 1-hexadenene), branched alkanes, branched alkenes and others. The same kind of compounds were also identified in the recycled materials at a similar concentration as in virgin ones. Virgin and recycled polyethylene contain also ethylbenzene and o-, m- and p-xylenes, where o-xylene had the largest peak of the four. The aromatic hydrocarbons are probably parts of additives, which degraded during extraction and sample preparation procedures. Aromatic hydrocarbons without functional groups, such as ethylbenzene and xylenes are considered highly toxic, but the height and area of their peaks suggest low concentrations. The concentration of these hazardous contaminants in the recycled resin is, however, approximately five times higher in recycled material, estimated by a comparison of the peak areas. Ethylbenzene and o-, m- and p-xylenes, o-xylene having the largest peak of the four were also identified in virgin and recycled polypropylene resins.

  • 18. Camacho, W.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Quantification of antioxidants in polyethylene by near infrared (NIR) analysis and partial least squares (PLS) regression2002In: IJPAC. International journal of polymer analysis and characterization, ISSN 1023-666X, E-ISSN 1563-5341, Vol. 7, no 02-jan, 41-51 p.Article in journal (Refereed)
    Abstract [en]

    Partial least squares (PLS) regression was used to generate a calibration model that can be used for the prediction of the content of two antioxidants, Irganox 10 10 and Irgafos 168, in high density polyethylene (HDPE). The samples containing levels of either one or both antioxidants in a range of 0-4500 ppm were analyzed by near infrared (NIR) in the diffuse reflectance mode. The samples were compounded in an extruder and subsequently analyzed as pellets, therefore, sample preparation was not required. High performance liquid chromatography (HPLC) was used as a reference method and the extraction of the antioxidants was performed either by microwave-assisted extraction (MAE) or ultrasonication. Data pretreatment of the raw NIR-data was necessary in order to eliminate the physical differences of the samples, e.g., size and shape. Multiple scattering correction (MSC) and second derivative of the raw data were used for this purpose. Root-mean-square error of prediction (RMSEP) for Irganox 1010 and Irgafos 168 was 46 and 97 ppm, respectively, when derived raw data was used,- similar results were obtained when calibration was performed on MSC data. The number of principal components was determined by cross-validation; in addition, the calibration model was validated with a test set.

  • 19. Camacho, W.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Simultaneous determination of molecular weight and crystallinity of recycled HDPE by infrared spectroscopy and multivariate calibration2002In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 85, no 2, 321-327 p.Article in journal (Refereed)
    Abstract [en]

    An attempt of correlating molecular weight (M,) of recycled high-density polyethylene (HDPE) as measured by size-exclusion chromatography (SEC) with diffuse reflectance near and mid-infrared spectroscopy (NIR/MIR) was made by means of multivariate calibration. The spectral data obtained was also used to extract information about the degree of crystallinity of the recycled resin. Differential scanning calorimetry (DSC) was used as the reference method. Partial leastsquares (PLS) calibration was performed on the MIR and NIR spectral data for prediction of Af, Four PC factors described fully the PLS models. The root-meansquare error of prediction (RMSEP) obtained with MIR data was 360, whereas a RMSEP of 470 was achieved when calibration was carried out on the diffuse reflectance NIR data. A PLS calibration for prediction of degree of crystallinity was performed on the NIR data in the 1100-1900-nm region, but the ability of prediction of this model was poor. However a PLS calibration in the region 2000-2500 nm yield better results. Four PC factors explained the most of the variance in the spectra and the RMSEP was 0.4 wt %.

  • 20. Camacho, W.
    et al.
    Valles-Lluch, A.
    Ribes-Greus, A.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Determination of moisture content in nylon 6,6 by near-infrared spectroscopy and chemometrics2003In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 87, no 13, 2165-2170 p.Article in journal (Refereed)
    Abstract [en]

    The effects of moisture on the morphology and mechanical properties of polyamides have been extensively studied by a number of researchers. However, the assessment of water content in the resins has been carried out by thermal or thermogravimetric methods, which are destructive. In the present work partial least-squares (PLS) calibration models based on near-infrared (NIR) spectroscopy were produced in order to predict the moisture content of nylon 6,6. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and the loss-on-drying (LOD) method were used as reference methods. TGA, LOD, DSC, and NIR analysis were performed in parallel, and the obtained data were used for multivariate calibration purposes. Data pretreatment techniques such as derivation and multiplicative scattering correction (MSC) successfully eliminated the baseline offset present in the raw spectra and compensated for differences in thickness and light scattering of the analyzed samples. Calibration models were validated by full cross validation with the help of a test set. A comparison of the prediction ability of PLS models based on pretreated data was also done. NIR spectroscopy is a rapid and nondestructive method for the determination of moisture in recycled nylon. The moisture content can be predicted with a RMSEP = 0.05 wt %.

  • 21.
    Camacho, Walker
    KTH, Superseded Departments, Polymer Technology.
    Analytical techniques for quality assessment of separated and commingled recycled polymer fractions2002Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Different methods for quality assessment of separated andcommingled plastics from household and electronic waste havebeen developed. Especial attention has been given tospectroscopic methods since they are non-destructive andrequire little or no sample preparation at all.

    A wide variety of low molecular weight compounds have beenidentified in recycled polyethylene (HDPE) and polypropylenefrom hard packaging waste by gas chromatography- massspectroscopy (GC-MS) after microwave assisted extraction (MAE).Low molecular weight substances such as alcohols, esters,ketones and fragrance and flavour compounds were detected inthe recycled resins. The major category of compounds identifiedin the virgin resins is conformed by aliphatic hydrocarbonssuch as alkanes and alkenes. It was found that theconcentration of aromatic hydrocarbons without functionalgroups, e.g. ethylbenzene and xylenes in recycled HDPE wasapprox. 5 times higher and equal to 120 and 35 ppb,respectively.

    The potential of near infrared (NIR) and Fourier transformRaman (FT-Raman) spectroscopy in combination with multivariateanalysis as a rapid, non-destructive and accurate analyticalmethod has been studied and the feasibility of these methodsfor at/in line characterisation of several properties ofrecyclates has also been explored.

    NIR in diffuse reflectance mode has been successfully usedfor quantification of antioxidants in polyethylene, thestandard error of prediction is almost comparable to the errorof wet methods, i.e., extraction plus liquid chromatography.The error of prediction of this method is 35 ppm for Irganox1010 and 68 ppm for Irgafos 168. The inaccuracy in thequantification of Irgafos 168 is due to the fact that thisantioxidant degrades during polymer processing.

    NIR and Mid-infrared (Mid-IR) worked well for fastdetermination of molecular weight and crystallinity of therecycled HDPE and acceptable errors of prediction, comparableto that of the reference methods, i.e. size exclusionchromatography (SEC) and differential scanning calorimetry(DSC) have been obtained.

    The present thesis also shows that NIR and Raman are goodcandidates for in/on line compositional analysis of mixedpolymer fractions from recycled plastic waste. Diffusereflectance NIR allows a rapid and reliable measurement ofpellets and requires no previous sample preparation. Thecomposition of binary blends can be determined with highaccuracy. The PP content in the PP/HDPE blends was predictedwith a RMSEP equal to 0.46 %w in the 0-15 %wt region and theRMSEP for PP in the PP/ABS blends was 0.3 %wt.

    The thermal and thermoxidative stability of recycled PP,HDPE and a 20/80 PP/HDPE blend subjected to multiple extrusionhave been studied by DSC, thermal analysis (TGA) andchemiluminiscence (CL). A decrease in Toxand OIT was observed after each extrusion step.The drop in OIT was sharper after the first two extrusions. TheOIT values produced by DSC and CL were in good agreement.However, CL provided more information about the oxidationprocess taking place in the blends.

    The moisture content in recycled polyamide 6,6 was readilydetermined by NIR in transmission mode and it could bepredicted with a RMSEP = 0.05 %wt. The accuracy of the methodappeared to be as good as that of the more time consumingthermal methods such as TGA, DSC and loss on dry (LOD), whichwere used as reference methods. The influence of differentamounts of water on the viscoelastic properties of nylon hasbeen investigated.

    Keywords:Recycling, HDPE, PP, blends, nylon 6,6, ABS,water content, MAE, GC-MS, NIR, FT-Raman, chemiluminiscence,low molecular weight compounds, antioxidant content,crystallinity, molecular weight, thermal stability,characterisation methods, analysis of polymers, blends.

  • 22.
    Carlmark, Anna
    KTH, Superseded Departments, Polymer Technology.
    Atom transfer radical polymerization from multifunctional substrates2002Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Atom transfer radical polymerization (ATRP) has proven to be a powerful technique to obtain polymers with narrow polydispersities and controlled molecular weight. It also offers control over chain-ends. The technique is the most studied and utilized of thecontrolled/”living” radical polymerization techniques since a large number of monomerscan be polymerized under simple conditions. ATRP can be used to obtain polymer graftsfrom multifunctional substrates. The substrates can be either soluble (i. e. based ondendritic molecules) or insoluble (such as gold or silicon surfaces). The large number ofgrowing chains from the multifunctional substrates increases the probability of inter-and intramolecular reactions. In order to control these kinds of polymerizing systems, andsuppress side-reactions such as termination, the concentration of propagating radicalsmust be kept low. To elaborate such a system a soluble multifunctional substrate, based on 3-ethyl-3-(hydroxymethyl)oxetane, was synthesized. It was used as a macroinitiatorfor the atom transfer radical polymerisation of methyl acrylate (MA) mediated byCu(I)Br and tris(2-(dimethylamino)ethyl)amine (Me6-TREN) in ethyl acetate at room temperature. This yielded a co-polymer with a dendritic-linear architecture. Since mostsolid substrates are sensitive to the temperatures at which most ATRP polymerisations are performed, lowering the polymerization temperatures are preferred. ATRP at ambienttemperature is always more desirable since it also suppresses the formation of thermally formed polymer. The macroinitiator contained approximately 25 initiating sites, which well mimicked the conditions on a solid substrate. The polymers had low polydispersity and conversions as high as 65% were reached without loss of control. The solid substrateof choice was cellulose fibers that prior to this study not had been grafted through ATRP.As cellulose fibers a filter paper, Whatman 1, was used due to its high cellulose content.The hydroxyl groups on the surface was first reacted with 2-bromoisobutyryl bromidefollowed by grafting of MA. Essentially the same reaction conditions were used that hadbeen elaborated from the soluble substrate. The grafting yielded fibers that were very hydrophobic (contact angles>100°). By altering the sacrificial initiator-to-monomer ratiothe amount of polymer that was attached to the surface could be tailor. PMA with degreesof polymerization (DP’s) of 100, 200 and 300 were aimed. In order to control that thepolymerizations from the surface was indeed “living” a second layer of a hydrophilicmonomer, 2-hydroxymethyl methacrylate (HEMA), was grafted onto the surface. Thisdramatically changed the hydrophobic behavior of the fibers.

  • 23.
    Claesson, Hans
    KTH, Superseded Departments, Polymer Technology.
    Rheology and UV-curing of a star-branched polyester2001Licentiate thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The use of powder coatings has increased steadily over thelast few decades. Their popularity is due to a number of majoradvantages they offer when compared to solvent-borne systems.Near zero VOC-content, reduced energy consumption and near 100%utilisation of the material are some of the advantages. Themain components in most thermoset powder coatings are a primaryresin and a binder. The coating is applied in powder form, thenbaked and cured i.e. cross-linked. Traditionally, thecross-link reaction has been controlled by temperature. Normalcuring temperatures range between 160 and 200 °C, and thusare not suitable for applications involving heat sensitivesubstrates such as wood and plastic. One way to lower thecuring temperature is by the introduction of semi-crystallinematerial with a suitable melting temperature. The advantage ofusing a crystalline resin is its rapid melting, a first ordertransition, versus the slow softening of an amorphous resin.Low curing temperature also requires an initiating system thatis activated at low temperatures while stable at roomtemperature. This is difficult to achieve with conventionalthermal initiators. In recent yearsUV-curing of powdercoatings has obtained increased attention in industrialresearch. This technique allows fast curing at lowertemperatures than conventional powder coatings. The researchinto UV-curing was triggered by the interest in using heatsensitive substrates. Other advantages are improved storagestability, elimination of premature reaction duringmanufacturing and better levelling since viscosity does notincrease until UV-irradiated. This thesis describes thesynthesis and characterisation of a series of branchedpolyesters and investigates their possible use as powdercoatings resins. The polyesters consist of poly(e-caprolactone)(PCL) (degree of polymerisation: 5-200) initiated fromhydroxyfunctional cores with methylmethacrylate end-capping .The cores utilised are: (1) 3rd-generation Boltorn, acommercially available hyperbranched polyester withapproximately 32 hydroxyl groups, (2) a 3rd-generationdendrimer with 24 hydroxyl groups, (3) a 3rd-generation dendronwith 8 hydroxyl groups, and (4) a linear PCL for comparison.All initiators are based on 2,2-bis(methylol) propionic acid(bis-MPA). The polymers and films were characterised using1H-NMR, 13C-NMR, SEC, rheometry, DMTA, DSC and a rheometercoupled with an UV-lamp. Measurements of zero shear rateviscosity showed that h0 increased exponentially with Mw, justas expected for star-branched polymers. For Boltorn-PCL anddendrimer-PCL, h0 is independent of Mw but dependant of the armMw (Ma). However, the dendron-PCL deviated from this behaviour.The dendron-PCL Ma was higher than that of Boltorn-PCL ordendrimer-PCL at the same h0. The resins are crystalline andthe melting points range from 34-50 °C; films can beformed and cured below 80 °C. Measurement of mechanicalproperties of cured films showed that the films from the low Mwpolymer were amorphous while those with high Mw werecrystalline. The viscoelastic behaviour during the fast cureshowed that the time to reach the gel point, a few seconds,increased linearly with molecular weight. The crossover ofG’and G’’was used as the gel point.

  • 24.
    Claesson, Hans
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Malmström, Eva
    KTH, Superseded Departments, Polymer Technology.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Synthesis and characterisation of star branched polyesters with dendritic cores and the effect of structural variations on zero shear rate viscosity2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 12, 3511-3518 p.Article in journal (Refereed)
    Abstract [en]

    A series of branched polyesters consisting of poly(epsilon-caprolactone) (PCL) (degree of polymerisation: 5-200) initiated from hydroxy-functional cores and end-capped with methylmethacrylate have been prepared. The cores were third-generation hyperbranched polyester, Boltorn, with approximately 32 hydroxyl groups, a third-generation dendrimer with 24 hydroxyl groups and a third-generation dendron with eight hydroxyl groups. Finally, a linear PCL was synthesised as a reference material. All initiators were based on 2,2-bis(methylol) propionic acid (bis-MPA). C-13 NMR spectra of the polymers showed that those with shorter arms contained unreacted hydroxyl groups on the core. Rheological measurements of zero shear rate viscosity, eta(0), showed that the branched polyesters had a considerably lower eta(0) than linear polyester with similar molecular weight. The low melt viscosity and the crystallity produced a theological behaviour suitable for the film formation process for powder coatings. Measurements of mechanical properties of cured films showed that those with low arm molecular weight, M-a, were amorphous while those of high M-a were crystalline.

  • 25.
    Claesson, Hans
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Malmström, Eva
    KTH, Superseded Departments, Polymer Technology.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Doyle, M.
    Manson, J. A. E.
    Rheological behaviour during UV-curing of a star-branched polyester2002In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 44, no 1, 63-67 p.Article in journal (Refereed)
    Abstract [en]

    Using a rheometer coupled with an UV-light generator, the viscoelastic behaviour during the fast cure of star-branched polyester is investigated. The 32 arm star polymers consist of a hyperbranched polyester core, Boltorn(TM) and linear grafts of poly(E-caprolactone) (degree of polymerisation: 20-52) with methacrylate end groups. The resins are crystalline and the melting points range from 34 to 50degreesC; films can be formed and cured below 80degreesC. The crossover of G' and G was used as the gel point. The time to reach the gel point, a few seconds, increases linearly with molecular weight.

  • 26.
    Claesson, Hans
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Scheurer, Curzio
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Malmström, Eva
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Paulus, W.
    Schwalm, R.
    Semi-crystalline thermoset resins: tailoring rheological properties in melt using comb structures with crystalline grafts2004In: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 49, no 1, 13-22 p.Article in journal (Refereed)
    Abstract [en]

    Thermosetting resins with semi-crystalline grafts have been synthesized. An amorphous resin with epoxide groups was first functionalized with hydroxyl groups using 2,2-bis(methylol) propionic acid, bis-MPA in bulk at 155 degreesC. Functionalization with bis-MPA was monitored using FT-IR, FT-Raman and SEC. The reaction was complete in 30 min. Grafts of poly(epsilon-caprolactone) were then grown from the hydroxyl functional resin and end capped with methacrylate groups. The polymerization Of epsilon-caprolactone, performed in bulk at 110 degreesC using Sn(Oct)(2), was characterized using H-1 NMR and SEC. The obtained molecular weights agreed well with theoretical values. The final end capping was performed using methacrylic anhydride, and monitored with SEC and H-1 NMR, which indicated full substitution. Two combs were synthesized with different arm lengths, DP 10 and 20, and the obtained M-W were close to calculated values. The complex viscosity was measured from low to high temperature for the crystalline resins, the amorphous resin and blends thereof. Rheological data show a rapid decrease in viscosity within a temperature change of 10-15 degreesC for the crystalline resins while the amorphous resin exhibited a slow softening. The blends exhibited a behavior in-between that of the crystalline and the amorphous resin. Films were prepared from the pure resins and the blends. The films were cured using UV irradiation. The comb architecture of these resins has advantages such as crystallinity, high molecular weight and low viscosity, facilitating leveling and resulting in smooth films. The final film properties varied with the ratio of crystalline to amorphous resin, where increase in the amount of crystalline resin correlated with increased the flexibility.

  • 27. Contat-Rodrigo, L.
    et al.
    Haider, N.
    Ribes-Greus, A.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Ultrasonication and microwave assisted extraction of degradation products from degradable polyolefin blends aged in soil2001In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 79, no 6, 1101-1112 p.Article in journal (Refereed)
    Abstract [en]

    Two nonconventional extraction techniques, microwave assisted extraction (MAE) and ultrasonication, were used to extract degradation products from polyolefins with enhanced degradability. High-density polyethylene/polypropylene blends with two different biodegradable additives (a granular starch/iron oxide mixture and Mater-Bi AF05H) were subjected to outdoor soil burial tests and removed at different periods of time between 0 and 21 months. The extracted products were analyzed by gas chromatography mass spectrometry (GC-MS). Ultrasonication was found to be a more suitable technique than MAE because of better reproducibility. In addition, higher amounts of certain products (e.g., carboxylic acids) were extracted by ultrasonication than by MAE. The degradation products extracted from the two blends were basically a homologous series of alkanes, alkenes, carboxylic acids, and alcohols. The amount of hydrocarbons (saturated and unsaturated) and alcohols remained basically the same as the degradation times increased. However, carboxylic acids tended to decrease slightly with the exposure time. Their concentration remained practically unchanged until 12 months of soil burial when a more significant decrease was noted. The quantitative analysis of the degradation products revealed for both samples a decrease in the amount of carboxylic acids with the exposure time, although the trend was different according to the additive used in each sample. For blends with Mater-Bi the amount of carboxylic acids was at a minimum after 12-month exposure in soil, which coincided with a minimum in the molecular weight distribution. After blends with granular starch/iron oxide were exposed to 3 months in soil, tetradecanoic acid was no longer detectable and the amount of hexadecanoic and octadecanoic acids decreased significantly. Solid-phase microextraction, a solvent-free extraction technique, was used to extract the degradation products that could have migrated to the soil from blends with Mater-Bi. Small amounts of tetradecanoic acid and dodecanol were identified by GC-MS in the soil surrounding the sample. The degradation patterns observed here correlate with our previous results from mechanical and morphological characterization of these samples.

  • 28. Coullerez, G.
    et al.
    Lundmark, S.
    Malkoch, Michael
    KTH, Superseded Departments, Polymer Technology.
    Magnusson, H.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Mathieu, H. J.
    Insights into ToF-SIMS analysis of dendritic macromolecules: cationization and PCA to probe their molecular weight on surfaces2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 203, 620-624 p.Article in journal (Refereed)
    Abstract [en]

    Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is utilized to study dendrons, dendrimers and hyperbranched derivatives prepared from the 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) or the 3-ethyl-3-(hydroxymethyl)oxetane (TMPO). We show that the cationization experiments of the intact molecules with alkali or metal ions such as Na+, Cu+ or Ag+ allow to detect whole molecular species up to 3000 Da (low generation). It allows to probe directly their molecular TM weight and end-functionality. However, when the molecule lift-off fails for series of hyperbranched polyesters Boltorn(TM), the fingerprint part of the SIMS spectra (m/z < 300 Da) is instead used. The low-mass fragments are mainly assigned to the bis-MP repeating unit. Ions due to the core molecule are also distinguished. Data treatment is combined with the principal component analysis (PCA) multivariate statistical method to highlight the main differences between the spectra. Only one principal component (PC1) is needed to describe most of the variance between the samples taking into account the generation effect. PC1 plotted as a function of the molecular weight gives a calibration curve. Normalization of the data set by ion intensities from the core molecule allows the linearization of the SIMS intensities vs. the molecular weight.

  • 29. Coullerez, G.
    et al.
    Lundmark, S.
    Malmström, Eva
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Mathieu, H. J.
    ToF-SIMS for the characterization of hyperbranched aliphatic polyesters: probing their molecular weight on surfaces based on principal component analysis (PCA)2003In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 35, no 8, 693-708 p.Article in journal (Refereed)
    Abstract [en]

    A series of 2,2-bis(hydroxymethyl)propionic acid (Bis-MPA) hyperbranched aliphatic polyesters with different molecular weights (generations) is analysed for the first time by time-of-flight secondary ion mass spectrometry (ToF-SIMS). The main negative and positive low-mass fragments are identified in the fingerprint part of the spectra (m/z < 400) and are principally assigned to fragmentation of the Bis-MPA repeating units. In addition, it is shown that the fragmentation pattern is highly affected by the functional end-groups. This is illustrated for a phthalic acid end-capped hyperbranched polymer and for an acetonide-terminated dendrimer analog. Also, typical fragments assigned to the ethoxylated pentaerythritol core molecule are detected. These ions show decreasing intensities with increasing molecular weight. This intensity dependency on the generation is used to calibrate the molecular weight of hyperbranched polyesters on the surface. To obtain quantitative information, a principal component analysis WCA) multivariate statistical method is applied to the ToF-SIMS data. The influence of different normalization procedures prior to PCA calculation is tested, e.g. normalization to the total intensity, to the intensities of ions assigned to the Bis-MPA repeating unit or to intensities of fragments due to the core molecule. It is shown that only one principal component (PC1) is needed to describe most of the variance between the samples. In addition, PC1 takes into account the generation effect. However, different relationships between the PC1 scores and the hyperbranched mass average molecular weights are observed depending on the normalization procedure used. Normalization of data set ion intensities by ion intensities from the core molecule allows linearization of the SIMS intensities versus the molecular weight and allows the hyperbranched polymers to be discriminated up to the highest generations. In addition, PCA applied to ToF-SIMS data provides an extended interpretation of the spectra leading to further identification of the correlated mass peaks, such as those of the Bis-MPA repeating unit (terminal, dendritic and linear) and those of the core molecule. Finally, the work presented demonstrates the extreme potential of the static ToF-SIMS and PCA techniques in the analysis of dendritic molecules on solid surfaces.

  • 30. Coullerez, G.
    et al.
    Mathieu, H. J.
    Lundmark, S.
    Malkoch, Michael
    KTH, Superseded Departments, Polymer Technology.
    Magnusson, H.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Cationization of dendritic macromolecule adsorbates on metals studied by time-of-flight secondary ion mass spectrometry2003In: Surface and Interface Analysis, ISSN 0142-2421, E-ISSN 1096-9918, Vol. 35, no 8, 682-692 p.Article in journal (Refereed)
    Abstract [en]

    Time-of-flight secondary ion mass spectrometry (ToF-SIMS) was utilized to study dendritic macromolecules with various architectures, such as dendrons, dendrimers and hyperbranched polyesters prepared from bis-(hydroxymethyl)propionic acid (Bis-MPA) and a series of hyperbranched polyethers based on 3-ethyl-3(hydroxymethyl)oxetane. The measurements were performed on spin-coated thin films of the branched molecules (D) onto silicon, chemically etched copper foil and silver-coated wafers. They showed weak signatures of molecular ions by proton capture (D + H)(+) in the high mass range of the spectra (m/z > 400). On the contrary, cationization of the intact molecules with alkali or transition metal ions such as Na+, Cu+ or Ag+ was observed. High-intensity quasi-molecular ions (D + M)(+) (with M = Na+, Cu+ or Ag+) allowed the studied polymers to be identified. The whole molecular species were observed for Bis-MPA dendrons and dendrimers up to 3000 Da for hydroxyl or acetonide-terminated derivatives. The success of the so-called cationization experiments with metal substrates compared with analysis of molecular adsorbates on silicon is highlighted. The ToF-SIMS sensitivity appeared useful to provide information about the molecular end-groups or to highlight incomplete reaction occurring during some deprotection step of the synthesis. Only uncationized fragments of low masses were detected for the hyperbranched polyesters. This result suggested the effect of molecular asymmetry and/or flattening of the molecules on the substrates, which hampered the molecule lift-off efficiency. Nevertheless, the hyperbranched polyethers were characterized based on the peak distribution of intensities, which allowed estimation of their molecular weight average. This work was intended to illustrate the capabilities of ToF-SIMS to analyse dendritic polymers on surfaces.

  • 31.
    Edlund, Ulrica
    KTH, Superseded Departments, Polymer Technology.
    Design of new biodegradable polymer matrices for controlled drug delivery2000Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Conventional drug administration technologies display poorcontrollability, and lead to high plasma concentrations andshort duration times, which frequently lead to adverse effects.Controlled release technology aims at predictable andreproducible delivery of an active substance over an extendedperiod of time, yielding optimal response and prolongedefficiency, and thus offering considerable improvement of manytreatments. A powerful approach to controlled drug delivery isthe incorporation of the drug into a biodegradable polymericmatrix, which distributes the active substance in a controlledand sustained fashion as the polymer erodes.

    This thesis describes the design of novel biodegradablepolymer matrices for controlled and sustained drug delivery.New functional and biodegradable materials with variableproperties were obtained by homopolymer blending andcopolymerization of building blocks with specific, desirableproperties; poly(adipic anhydride) (PAA), poly(trimethylenecarbonate) (PTMC), poly(1,5-dioxepan-2-one) (PDXO),poly(L-lactide) (PLLA), poly(D,L-lactide) (PDLLA), andpoly(L-lactide-co-1,5-dioxepan-2-one) (P(L-LA-co-DXO).Techniques were developed for the preparation of drug-releasingmatrices in the form of films and microspheres. Variousanalysis techniques, including Differential ScanningCalorimetry,1H-Nuclear Magnetic Resonance, InfraredSpectrometry, Scanning Electron Microscopy, Size ExclusionChromatography and UV-VIS Spectroscopy, were used forcharacterization.

    Microspheres encapsulating therapeutic substances wereprepared from P(L-LA-co-DXO) and blends of PDXO with PLLA orPDLLA. The properties, storage stability,degradation and drugrelease characteristics of these matrices were explored,compared and evaluated with special regard to the morphologyand its impact on thein vitrobehavior. Sustained release of drugs wasobtained. The mode of release was strongly influenced by thehydrophilicity of the drug, and by the copolymer/blendcomposition and morphology. The lactide:DXO composition wasproven to be a versatile tool to control the morphology and inturn the rates and pattern of erosion and diffusion ofencapsulated agents from the matrices.

    Films were prepared from PTMC-PAA blends, in which PAA actedas a plasticizer. Loss of the fast-degrading PAA componentenhanced the porosity and hydration of the slow-degrading PTMC.A statistical full factorial model was designed to elucidatethe influence of matrix parameters and their interactions. ThePTMC-PAA ratio, the molecular weight of the PTMC, andinteractions amongst these factors significantly influenced therelease performance, mass loss and degree of plasticization andthe relationships obtained enabled the erosion and drug releasepattern to be predicted and controlled. Moisture uptake,storage stability at different relative humidities, and thesterilizability were determined to further explore theversatility of PTMC-PAA matrices. Thein vivolocal tissue response and biocompatibility ofPTMC-PAA implants was assessed in the anterior chamber ofrabbits eyes for 1 month. PTMC-rich matrices displayed goodbiocompatibility.

    Key factors that regulate the biological activity of thesepolymeric vehicles were identified as drug solubility,composition, molecular weight, stereochemical configuration,and morphology. By careful design, the degradation and drugrelease characteristics, e.g. kinetics and duration, can bealtered over a broad spectrum. This study shows that structuralchanges of the polymer backbone, and the modeling ofcomposition and morphology provide powerful means of tailoringsystems for specific applications.

    Keywords: controlled release, drug delivery, microspheres,polylactide, poly(1,5-dioxepan-2-one), poly(adipic anhydride),poly(trimethylene carbonate), degradation, blends

  • 32.
    Edlund, Ulrica
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, A. C.
    Degradable polymer microspheres for controlled drug delivery2002In: Advances in Polymer Science, ISSN 0065-3195, E-ISSN 1436-5030, Vol. 157, 67-112 p.Article, review/survey (Refereed)
    Abstract [en]

    Controlled drug delivery technology is concerned with the systematic release of a pharmaceutical agent to maintain a therapeutic level of the drug in the body for a sustained period of time. This may be achieved by incorporating the therapeutic agent into a degradable polymer vehicle, releasing the agent continuously as the matrix erodes. This review is concerned with degradable polymers for use in controlled drug delivery with emphasis on the preparation, applications, biocompatibility, and stability of microspheres from hydrolytically degradable polymers.

  • 33.
    Edlund, Ulrica
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Copolymerization and polymer blending of trimethylene carbonate and adipic anhydride for tailored drug delivery1999In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 72, no 2, 227-239 p.Article in journal (Refereed)
    Abstract [en]

    The copolymerization in bulk and solution of trimethylene carbonate (TMC) with adipic anhydride (AA) as well as the blending of homopolymers are described. We show experimentally that the components are not copolymerizable but partially miscible, forming a microscopic dispersion without any visible signs of phase separation. Poly(adipic anhydride) (PAA) functions as a plasticizer, permitting an increase in the erosion rate by increasing the porosity and hydration. Drug delivery from the blends was evaluated. A statistical factorial model was designed to explore the influence of three important blend parameters and their interactions, making it possible to predict the erosion and drug-release behavior of the blend matrices. The PAA:poly(trimethylene carbonate) (PTMC) ratio and molecular weight of the polycarbonate component significantly influence the drug-release performance, mass loss, and degree of plasticization. The interaction among these factors also influences the blend properties. Plasticization of PTMC enhances the drug release to an extent that is dependent on the amount of PAA used. We demonstrate that blending offers a convenient alternative to copolymerization for the preparation of polymer matrices with predictable drug delivery.

  • 34.
    Edlund, Ulrica
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Microspheres from poly(D,L-lactide)/poly(1,5-dioxepan-2-one) miscible blends for controlled drug delivery2000In: Journal of bioactive and compatible polymers (Print), ISSN 0883-9115, E-ISSN 1530-8030, Vol. 15, no 3, 214-229 p.Article in journal (Refereed)
    Abstract [en]

    Novel biodegradable microspheres were designed from blends of poly(D,L-lactide) (PDLLA) and poly(1,5-dioxepan-2-one) (PDXO). The addition of PDXO to PDLLA yielded a more pliable and versatile matrix, where the properties can be controlled by means of composition. The components were fully miscible and formed homogeneous, amorphous, smooth and dense microspheres. Blend composition was a vital factor in determining the blend properties, morphology and in vitro degradation. Diclofenac sodium, a non-steroidal anti-inflammatory drug, was incorporated into PDLLA-PDXO microspheres of various composition ratios. Sustained release of drug was obtained. The degradation and release rates of PDLLA-PDXO microspheres were dependent on the blend composition, providing a powerful means of controlling drug delivery.

  • 35.
    Edlund, Ulrica
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Morphology engineering of a novel poly(L-lactide)/poly(1,5-dioxepan-2-one) microsphere system for controlled drug delivery2000In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 38, no 5, 786-796 p.Article in journal (Refereed)
    Abstract [en]

    Morphology is presented as a powerful tool to control the in vitro degradation and drug release characteristics of novel drug delivery microspheres prepared from homopolymer blends of 1,5-dioxepan-2-one, DXO, and L-lactide, L-LA. Their performance in this respect was compared to analogous P(L-LA-co-DXO) microspheres. Blends formed denser and less porous microspheres with a higher degree of matrix crystallinity than copolymers of corresponding L-LA:DXO composition. The morphology differences of blends and copolymers, further adjustable by means of component ratio, are shown to have a vital impact on the in vitro performance. Sustained drug delivery was obtained from both copolymers and blends. Molecular weight; loss was retarded and diffusion-mediated release was inhibited in the latter case, further delaying the release process. The effects of storage on the physicochemical properties of these systems were evaluated under desiccated and moist conditions for 5 months. Storage-induced physicochemical changes, such as matrix crystallization and molecular weight decrease, were accelerated at higher relative humidities. P(L-LA-co-DXO) demonstrated higher moisture sensitivity than a PLLA-PDXO blend of corresponding composition. The more crystalline and dense morphology of blend microspheres may thus be considered an improvement of the storage stability.

  • 36.
    Edlund, Ulrica
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Novel drug delivery microspheres from poly(1,5-dioxepan-2-one-co-L-lactide)1999In: Journal of Polymer Science Part A: Polymer Chemistry, ISSN 0887-624X, E-ISSN 1099-0518, Vol. 37, no 12, 1877-1884 p.Article in journal (Refereed)
    Abstract [en]

    Novel microspheres from copolymers of 1,5-dioxepan-2-one (DXO) and L-lactide (L-LA) were prepared by oil-in-water solvent evaporation and oil-in-oil solvent removal. The two preparation techniques were evaluated for sphere formulation and incorporation of two different drugs. Sustained release of these therapeutic substances was obtained. The consequences of altering the DXO : LA ratio, preparation method, and drug hydrophilicity were explored and identified as factors governing sphere quality, in vitro degradation, and drug release characteristics. We show that these relationships provide a powerful means of controlling the microsphere performance.

  • 37.
    Edlund, Ulrica
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Polyesters based on diacid monomers2003In: Advanced Drug Delivery Reviews, ISSN 0169-409X, E-ISSN 1872-8294, Vol. 55, no 4, 585-609 p.Article, review/survey (Refereed)
    Abstract [en]

    Polymers with ester linkages in their main chain comprise a family of polymers with immense diversity and versatility. This review deals with the preparation of such polymers from dicarboxylic acid monomers, and the result in terms of properties and applicability. Polyesters alone, and their copolymers with amides, anhydrides, urethanes, imides, ethers or other functional groups, offer countless opportunities to tune the properties of the resulting material within a broad range. Of particular interest is the inherent biodegradability of the ester linkage. Biodegradability is sought after in a wide range of applications, above all in the preparation of environmentally friendly polymers and biomedical materials for temporary surgical use and in drug delivery.

  • 38.
    Edlund, Ulrica
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Singh, K
    Fogelberg, I
    Lundgren, O
    Sterilization, storage stability and in vivo biocompatibility of poly(trimethylene carbonate)/poly(adipic anhydride) blends2000In: Biomaterials, ISSN 0142-9612, E-ISSN 1878-5905, Vol. 21, no 9, 945-955 p.Article in journal (Refereed)
    Abstract [en]

    Biodegradable blends of poly(trimethylene carbonate) (PTMC) and poly(adipic anhydride) (PAA) have been proven to be strong candidates for controlled drug delivery polymers in vitro. We now report on the stability, sterilizability and in vivo local tissue response of these matrices. Blend matrices were sterilized by beta-radiation or ethylene oxide gas treatment, stored at different times and temperatures, and analyzed for changes in physicochemical properties. Moisture uptake at different relative humidities and storage times was determined. Sterilization procedures induced hydrolysis of the matrices. Ethylene oxide gas sterilization had a significantly more marked effect upon the matrix properties than radiation treatment. The onset of degradation was reflected in a decrease of crystallinity and molecular weight along with a change of blend composition. A similar onset of matrix degradation was observed upon storage in air. The physicochemical properties of the blends were well preserved upon storage under argon atmosphere. Biocompatibility of PTMC/PAA implants was assessed in the anterior chamber of rabbits eyes for 1 month. At selected post-operative time points, aqueous humor was analyzed for white blood cells and the corneal thickness was measured. The results suggest good biocompatability of PTMC-rich matrices, whereas fast eroding PAA-rich matrices caused inflammatory responses, due to a burst release of degradation products.

  • 39. Eldsater, C.
    et al.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Changes in composition of hydrolyzed poly(butylene adipate-co-caproamide) characterized by pyrolysis-GC-MS, H-1-NMR and FTIR2000In: IJPAC. International journal of polymer analysis and characterization, ISSN 1023-666X, E-ISSN 1563-5341, Vol. 5, no 06-apr, 415-435 p.Article in journal (Refereed)
    Abstract [en]

    The changes in composition of an abiotically degraded polyester-amide, poly(butylene adipate-co-caproamide), in an aqueous environment at 37 degrees C; 60 degrees C and 80 degrees C were investigated. The changes in polymer composition were studied using pyrolysis-GC-MS, H-1-NMR, FTIR, and size exclusion chromatography, and degradation products were analyzed by solid-phase extraction and subsequent GC-MS. During the degradation of PEA in an aqueous environment, the main degradation products were 6-aminohexanoic acid, 1-hydroxydodecanoic acid-6-one-5-oxo and dimers. After longer degradation times and at higher degradation temperatures, 1-hydroxydodecanoic acid-6-one-5-oxo was cleaved further into hexanedioic acid and 1,4-butanediol. At 80 degrees C, the degradation was fastest with the largest weight loss due to dissolution of oligomer. At 80 degrees C, the amide content in the copolymer increased with increasing degradation time. We suggest that there is a two-step degradation mechanism with the formation of linear degradation products, where the hydrolysis of ester bonds is favored over that of amide bonds.

  • 40.
    Eldsäter, Carina
    KTH, Superseded Departments, Polymer Technology.
    Chemical and morphological characterisation of long-term properties of environmentally degradable polymers1999Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The environmental degradation of an aliphatic polyester,poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and a polyesteramide,poly(butylene adipate-co-amino caproate) (PEA) was studied to answer questionsregarding their life-time in natural environments,e.g.municipal solid waste compost. Characterisation oflong-term properties is done by a series of techniques. Inorder to predict long-term properties and lifetime ofdegradable polymers, it is necessary to compare morphologicalproperties,e.g.melting temperature and heat of fusion, withchemical properties, such as molecular weight, functional groupchanges and the evolution of degradation products.Pyrolysis-GC/GC-MS is also presented and discussed as a tool tostudy structural changes in polymers.

    PHBV was readily biodegradable and the major degradationpathway during composting was mediated by microorganisms. Theprimary degradation products formed during fungal degradationof PHBV were monomers and oligomers. These were furthermetabolised and converted into fatty acids, such as aceticacid, butanoic acid and pentanoic acid. The biodegradation wasaffected by the copolymer composition. Results indicated thatthe fungusAspergillus fumigatuspreferred 3-hydroxybutyrate unitsrather than 3-hydroxyvalerate units. Abiotic factors such asheat and moisture have less effect on the environmentaldegradation of PHBV in garden/household waste compost during aperiod of 50 days.

    PEA was less susceptible to biodegradation than PHBV. Noneof the fungiAspergillus fumigatus,Aspergillus nigerorPhanerochaete chrysosporiumwere able to grow on PEA ascarbon source. PEA was, however, sensitive to abiotic esterhydrolysis, especially at temperatures above 60°C, and wasreadily degraded through surface erosion. The fungaldegradation of PEA also occurred through surface erosion, butno preference for ester rather than amide bonds was observed.Degradation products formed during fungal degradation were1,4-butanediol, 1,6-hexanedioic acid, 6-aminocaproic acid and acomplex mixture of oligomers. Abiotic factors, such as heat incombination with moisture, have thus a large effect on thedecomposition of PEA in compost.

    Pyrolysis-GC/GC-MS is a promising tool to differentiatebetween degradation mechanisms of polymers, but needs furtherdevelopment for composition determination of biodegradablecopolymers.

    Keywords:polyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), polyesteramide, poly(butyleneadipate-co-amino caproate), degradation, fungi, composting,pyrolysis.

  • 41.
    Eriksson, Carl Axel
    et al.
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Björk, Folke
    KTH, Superseded Departments, Civil and Architectural Engineering.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Khabbaz, Farideh
    KTH, Superseded Departments, Polymer Technology.
    Två rapporter som behandlar: Kemisk nedbrytning av material i golvbjälklag1999Report (Other academic)
  • 42.
    Eriksson, Per-Arne
    KTH, Superseded Departments, Polymer Technology.
    Mechanical recycling of glass fibre reinforced polyamide 661997Doctoral thesis, comprehensive summary (Other scientific)
  • 43.
    Eriksson, Petter
    KTH, Superseded Departments, Polymer Technology.
    Oxidative spreading in polypropylene as studied by iImaging chemiluminescence2001Licentiate thesis, comprehensive summary (Other scientific)
  • 44.
    Erlandsson, Bengt
    KTH, Superseded Departments, Polymer Technology.
    Influence of the degradation mechanism on the molecular weight changes for some degradable polymers1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The influence of degradation mechanism on molecular weightchanges was investigated for certain degradable polymers. Thepolymers investigated were modified low density polyethylene(LDPE), poly(ethylene-co-vinyl alcohol) (EVOH) and aliphatic polyesters.

    Thermo- and photo-oxidation was studied for LDPE mixed withstarch and a pro-oxidant system, LDPE mixed with starch andLDPE alone. The chemical hydrolysis ofpoly(ε-caprolactone) (PCL) was also studied. The abioticdegradation of these materials was compared with thebiodegradation of LDPE mixed with starch and pro-oxidant, LDPEmixed with starch and LDPE inoculated withArthrobacter paraffineusorFusarium redolensandPenicillium simplicissimum.It was also compared withpoly(lactic acid) (PLA), poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and PCL degraded in compost.The degradation of PCL was also investigated in anaerobicsludge at two temperatures (37 and 55 ¡C).

    During the thermo-oxidation of the LDPE samples a decreasein molecular weight was seen. The samples with pro-oxidantshowed the fastest decrease in molecular weight. Starch had astabilising effect on LDPE during thermo-oxidation. During thephoto-oxidation an initial increase in molecular weight wasseen and was explained by a fast decomposition ofhydroperoxides during UV irradiation which lead to chainelongating reactions. Samples degraded by hydrolysis did sofaster at a higher temperature, while pH did not effect therate of degradation.

    When the modified LDPE samples were exposed tobiodegradation a decrease in the amount of carbonyls was seentogether with an increase in the amount of double bonds. At thesame time there was a small increase in molecular weight forthe biodegraded samples together with assimilation of thedegradation products or a larger amount of evolved14CO2. EVOH samples also displayed a slightly highermolecular weight after biodegradation together with a higheramount of14CO2. The micro-organisms assimilate faster the lowmolecular weight part of the samples, which explains theobserved increase in molecular weight. PLA and PHBV did notdisplay changes in molecular weight during composting. PCLdecreased its molecular weight during biodegradation, with afaster reduction in number average molecular weight (Mn) than weight average molecular weight (Mw). The same observations were made for the samplesexposed to thermophilic anaerobic sludge. This is indicative ofchain cleavage near the chain ends, which is associated withthe readier degradation of the amorphous regions where thechain ends are concentrated. During abiotic degradation thechain is cleaved mainly in a random fashion. PLA and PHBV didnot show any changes in molecular weight which is typical fordegradation byexo-enzymes. PCL showed a reduction in molecular weightas would be seen for polymers degraded byendo-enzymes. During the degradation of LDPE the polymerchanges in a way that affects the determination of molecularweight with size exclusion chromatography (SEC). The degradedpolymer will have a different relationship between molecularweight and hydrodynamic volume as compared to the undegradedpolymer. The observed molecular weight changes will, therefore,be incorrect if they are determined relative to a standard ofdifferent chemical type.

    Keywords:LDPE, polyethylene, starch, EVOH,poly(ethylene-co-vinyl alcohol), polyesters,poly(ε-caprolactone), PCL,14C-labelled, biodegradation, composting, anaerobicsludge, thermo-oxidation, photo-oxidation, chemical hydrolysis,molecular weight changes, size exclusion chromatography.

  • 45.
    Espert, Ana
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Camacho, Walker
    KTH, Superseded Departments, Polymer Technology.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Thermal and thermomechanical properties of biocomposites made from modified recycled cellulose and recycled polypropylene2003In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 89, no 9, 2353-2360 p.Article in journal (Refereed)
    Abstract [en]

    Residual cellulose fibers from the paper industry have been used as reinforcements in recycled polypropylene (PP) composites. The main obstacle to obtaining good properties with this biocomposite is deficiencies in the compatibility between the nonpolar matrices and the polar cellulose fibers used as reinforcements. The aim of this work was to improve the compatibilization between these cellulose fibers and the PP matrix with four different methods: modification by the addition of polypropylene-maleic anhydride copolymer (PPgMA) during the process of blending, preblending modification of the cellulose with a solution of PPgMA, modification of cellulose by silanes (vinyltrimethoxysilane), and acetylation of cellulose. Blends with all of the differently modified celluloses were prepared with the cellulose content varied up to 40%, and then all of the blends were subjected to thermal (differential scanning calorimetry and thermogravimetric analysis) and thermomechanical (dynamic mechanical thermal analysis) analyses. The results showed that the addition of cellulose fibers improved the thermomechanical behavior of the PP, increasing the value of the log of the dynamic modulus, and affected the thermal and thermooxidative behavior. Moreover, an advantage of the use of a recycled PP containing a small quantity of ethyl vinyl acetate (EVA) as a prime material in the composition was the enhancement of mechanical properties. The use of these methods for the modification of cellulose led to more desirable thermal and thermooxidative stabilities.

  • 46.
    Fahlén, Jesper
    KTH, Superseded Departments, Polymer Technology.
    Ultrastructural arrangement of the polymers in wood fibres2002Licentiate thesis, comprehensive summary (Other scientific)
  • 47. Fateh-Alavi, K.
    et al.
    Gallstedt, M.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    The effect of antioxidants on the surface oxidation and surface cracking of crosslinked polydimethylsiloxane2001In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 74, no 1, 49-57 p.Article in journal (Refereed)
    Abstract [en]

    Crosslinked polydimethylsiloxanes with three different chain-breaking antioxidants (Irganox 1076, Irganox 565 and Tinuvin 770) were exposed to air plasma (GHz), and the surface structures of the exposed samples were assessed by contact angle measurements, X-ray photoelectron spectroscopy, optical and scanning electron microscopy, and surface profilometry before and after uniaxial stretching. It was found that samples containing antioxidants oxidized more slowly than the reference sample with no antioxidant. Higher doses of air plasma were required to form a brittle silica-like layer in the samples with antioxidant than in the reference sample with no antioxidant. Tinuvin 770 showed the strongest antioxidative effect whereas Irganox 1076 and Irganox 565 were similar in efficiency.

  • 48. Fateh-Alavi, K.
    et al.
    Nunez, M. E.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    The effect of stabilizer concentration on the air-plasma-induced surface oxidation of crosslinked polydimethylsiloxane2002In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 78, no 1, 17-25 p.Article in journal (Refereed)
    Abstract [en]

    The concentrations of three stabilizers-a hindered phenol (Irganox 1076), a hindered amine light stabilizer (Tinuvin 770) and a bifunctional stabilizer with chain-breaking hindered phenol and secondary amine and hydroperoxide-decomposing sulphide moieties (Irganox 565)-in crosslinked polydimethylsiloxane were varied using swelling solutions of the stabilizers at different concentrations. The concentration of the stabilizer in the rubber was assessed by UV-Vis spectroscopy of Soxhlet and microwave assisted extracts. Irganox 1076 and Tinuvin 770 were soluble in polydimethylsiloxane to at least 0.2-0.3 wt.%, whereas the solubility of Irganox 565 was considerably lower. The samples were exposed to GHz air plasma and the surface structures of the exposed samples were studied by X-ray photoelectron spectroscopy, and by optical and scanning electron microscopy after uniaxial stretching. The plasma exposure time required for the formation of an oxidised glassy layer increased in a linear fashion with increasing stabilizer concentration, suggesting that the consumption rate was constant in time during the plasma exposure. Tinuvin 770 showed the strongest overall protecting effect whereas Irganox 565 showed the strongest protecting effect per mass fraction of stabilizer. Irganox 1076 was of moderate efficiency. The results suggest that efficient protection towards air plasma is achieved with hindered amine stabilizers or with stabilizers combining chain-breaking and hydroperoxide-decomposing functions. Differential scanning calorimetry showed that Tinuvin 770 and Irganox 565 protected polydimethylsiloxane against thermal oxidation at elevated temperatures. The chemical consumption of these stabilizers followed basically the classical scheme with zero-order kinetics and a rate constant obeying the Arrhenius law.

  • 49.
    Fateh-Alavi, Kamyar
    KTH, Superseded Departments, Polymer Technology.
    The effects of stabilizers on the air-plasma-induced surface oxidation of polydimethylsiloxane2001Licentiate thesis, comprehensive summary (Other scientific)
  • 50.
    Fateh-Alavi, Kamyar
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Effect of stabilizers on surface oxidation of silicone rubber by corona discharge2004In: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 84, no 3, 469-474 p.Article in journal (Refereed)
    Abstract [en]

    Crosslinked polydimethylsiloxane (PDMS) containing Irganox(R) 1076, Tinuvin(R) 770 or lrganox(R) 565, prepared by swelling PDMS in a solution of one of these stabilizers in n-hexane, was exposed to a corona discharge and the corona exposure time (tau(crit)) to form a brittle, silica-like layer was determined by optical microscopy. The critical corona exposure time showed a linear increase with increasing stabilizer concentration; Tinuvin 770 showed the highest efficiency and Irganox 1076 the lowest. The increase in tau(crit) on corona exposure of the stabilized samples with reference to the value for unstabilized PDMS was similar to that reported earlier for air plasma exposed samples. The efficiency of the stabilizers towards corona-induced surface oxidation of PDMS was also confirmed by X-ray photoelectron spectroscopy.

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