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  • 1. Albertsson, A-C.
    et al.
    Barenstedt, C.
    Karlsson, S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Lindberg, T.
    Degradation product pattern and morphology changes as means to differentiate abiotically and biotically aged degradable polyethylene1995In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 36, no 16, p. 3075-83Article in journal (Refereed)
  • 2. Bayley, G. M.
    et al.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Mallon, P. E.
    Large strain and toughness enhancement of poly(dimethyl siloxane) composite films filled with electrospun polyacrylonitrile-graft-poly(dimethyl siloxane) fibres and multi-walled carbon nanotubes2011In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 52, no 18, p. 4061-4072Article in journal (Refereed)
    Abstract [en]

    Unfilled cross-linked poly(dimethyl siloxane) (PDMS) is a weak material and is generally filled with high levels of particulate fillers such as silica, calcium carbonate and carbon black to improve its mechanical properties. The use of fibrous fillers such as electrospun nanofibres and multi-walled carbon nanotubes as fillers for PDMS has not been widely studied. In this study anew copolymer, polyacrylonitrile-graft-poly(dimethyl siloxane) (PAN-g-PDMS), is used as fibrous filler for PDMS. The graft copolymer is electrospun to produce the fibre filler material. It is shown how the PDMS content of the graft copolymer provides increased compatibility with silicone matrices and excellent dispersion of the fibre fillers throughout a silicone matrix. It is also shown that it is possible to include multi-walled carbon nanotubes in the electrospun fibres which are subsequently dispersed in the PDMS matrix. Fibre mats were used in the non-woven and the aligned forms. The differently prepared fibre composites have significantly different mechanical properties. Conventional composites using fibrous fillers usually show increased strength and stiffness but usually with a resultant loss of strain. In the case of the composites produced in this study there is a dramatic improvement in the extensibility of the non-woven PAN-g-PDMS fibre mat filled silicone films of up to 470%.

  • 3.
    Boujemaoui, Assya
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Mazieres, Stephane
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Destarac, Mathias
    Carlmark, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    SI-RAFT/MADIX polymerization of vinyl acetate on cellulose nanocrystals for nanocomposite applications2016In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 99, p. 240-249Article in journal (Refereed)
    Abstract [en]

    In the present work, poly(vinyl acetate) grafted cellulose nanocrystals (CNC-g-PVAc) were prepared via surface initiated reversible addition-fragmentation chain transfer and macromolecular design via the interchange of xanthates (SI-RAFT/MADIX) polymerization. Successful grafting of PVAc from CNC was confirmed by FT-IR and TGA analysis. PVAc nanocomposites reinforced with CNC-g-PVAc, as well as pristine CNC for comparison, of different weight percentages (0.5, 1, 3 and 5 wt%) of CNC were prepared via solvent casting. The PVAc reinforced with CNC-g-PVAc resulted in higher transparency and improved mechanical properties compared with unmodified CNC nanocomposites. The addition of 5 wt% CNC-g-PVAc increased the modulus of neat PVAc with as much as 154%. The proposed SI-RAFT/MADIX on CNC could be applied to wide range of monomers, and it is believed to be an efficient and robust method for CNC functionalization, thus expanding the potential applicability of CNC.

  • 4.
    Carlmark, Anna E
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Vestberg, Robert
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Malmström Jonsson, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Atom transfer radical polymerization of methyl acrylate from a multifunctional initiator at ambient temperature2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 15, p. 4237-4242Article in journal (Refereed)
    Abstract [en]

    A multifunctional initiator for ATRP has been synthesized by reacting a hyperbranched polyether, based on 3-ethyl-3-(hydroxymethyl)oxetane, with 2-bromo-isobutyrylbromide. The macroinitiator contained approximately 25 initiating sites per molecule. It was used for the atom transfer radical polymerization of methyl acrylate mediated by Cu(I)Br and tris(2-(dimethylamino)ethyl)amine (Me-6-TREN) in ethyl acetate at room temperature. This yielded a co-polymer with a dendritic-linear architecture. The large number of growing chains from each macromolecule increases the probability of inter-and intramolecular reactions. In order to control these kinds of polymerizing systems and prevent them from forming a gel, the concentration of propagating radicals must be kept low. The polymerizations under these conditions were well controlled. When a ratio of initiating sites-to-catalyst of 1:0.05 was used, the polymers from all of the reactions had a low polydispersity, ranging from 1.1 to 1.4. None of the polymerizations under these conditions gave gelation. Monomer conversions as high as 65% were reached while maintaining control over the polymerization. (C) 2002 Elsevier Science Ltd. All rights reserved.

  • 5. Chang, B.
    et al.
    Schneider, K.
    Patil, N.
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology. DESY, Hamburg, Germany.
    Heinrich, G.
    Microstructure characterization in a single isotactic polypropylene spherulite by synchrotron microfocus wide angle X-ray scattering2018In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 142, p. 387-393Article in journal (Refereed)
    Abstract [en]

    Position-resolved microstructure in a single spherulite of iPP is quantitatively studied by synchrotron microfocus wide angle X-ray scattering. The results show that the normal of mother lamellae in a spherulite is aligned mainly perpendicular to the radius, and the subsidiary daughter lamellae are inclined 80.75° with respect to that of the dominant mother lamellae. The crystallinity in the spherulite is in the range of 46%–56%, which is rarely influenced by the crystallization temperature. The ratio between the daughter lamellae and the mother lamellae is 0.18 when iPP crystallizes at 138 °C and it decreases to 0.11 as the crystallization temperature is decreased to 130 °C. The b-axis and c-axis in the mother lamellae tend to orient perpendicular to the radius direction, and the a-axis prefers to align in the radius direction.

  • 6.
    Chang, Baobao
    et al.
    Leibniz Inst Polymer Res Dresden, Dresden, Germany.;Tech Univ Dresden, Inst Werkstoffwissensch, Dresden, Germany..
    Schneider, Konrad
    Leibniz Inst Polymer Res Dresden, Dresden, Germany..
    Patil, Nilesh
    Leibniz Inst Polymer Res Dresden, Dresden, Germany..
    Roth, Stephan V.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Biocomposites. DESY, Hamburg, Germany.
    Heinrich, Gert
    Leibniz Inst Polymer Res Dresden, Dresden, Germany.;Tech Univ Dresden, Inst Text Maschinen & Text Hochleistungswerkstof, Dresden, Germany..
    Microstructure characterization in a single isotactic polypropylene spherulite by synchrotron microfocus wide angle X-ray scattering2018In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 142, p. 387-393Article in journal (Refereed)
    Abstract [en]

    Position-resolved microstructure in a single spherulite of iPP is quantitatively studied by synchrotron microfocus wide angle X-ray scattering. The results show that the normal of mother lamellae in a spherulite is aligned mainly perpendicular to the radius, and the subsidiary daughter lamellae are inclined 80.75 degrees with respect to that of the dominant mother lamellae. The crystallinity in the spherulite is in the range of 46%-56%, which is rarely influenced by the crystallization temperature. The ratio between the daughter lamellae and the mother lamellae is 0.18 when iPP crystallizes at 138 degrees C and it decreases to 0.11 as the crystallization temperature is decreased to 130 degrees C. The b-axis and c-axis in the mother lamellae tend to orient perpendicular to the radius direction, and the a-axis prefers to align in the radius direction.

  • 7.
    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, p. 3511-3518Article 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.

  • 8. Cordova, A
    et al.
    Iversen, T
    Martinelle, M
    KTH, School of Biotechnology (BIO), Biochemistry (closed 20130101).
    Lipase-catalysed formation of macrocycles by ring-opening polymerisation of epsilon-caprolactone1998In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 39, no 25, p. 6519-6524Article in journal (Refereed)
    Abstract [en]

    Studies were undertaken to gain mechanistic information on lactone ring-opening polymerisation reactions using Candida antarctica lipase B (Novozym 435) as the catalyst and epsilon-caprolactone as the monomer. Polymerisations were performed in organic solvents as well as without solvent at 60 degrees C. Candida antarctica lipase B catalysed concurrently with the intermolecular ring-opening polymerisation, and also the formation of macrocycles by an intramolecular condensation reaction. Candida antarctica lipase B had the highest initial rate of consumption of epsilon-caprolactone (1.2 mu mol mg(-1) min(-1)) in the bulk polymerisation, without solvent. Under these conditions, the highest average M-w, 4701 D, of poly(epsilon-caprolactone) was obtained. There were small amounts of cyclic oligomers present. When comparing the polymerisations performed in dioxane, acetonitrile and THF after 24 h reaction time with the bulk polymerisation, the average M-w of poly(epsilon-caprolactone) [2984, 1297, 1862 D, respectively] and the initial rates of monomer conversion of the enzyme (0.1, 0.05, 0.013 mu mol mg(-1) min(-1), respectively) were lower, however, the formation of cyclic oligomers was high. In dioxane, macrocycles of up to 2623 D corresponding to 23 monomer units were formed, and in acetonitrile there were mostly cyclic oligomers present. (C) 1998 Elsevier Science Ltd. All rights reserved.

  • 9. Eldsäter, C.
    et al.
    Erlandsson, B.
    Renstad, R.
    Albertsson, A-C.
    Karlsson, S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    The biodegradation of amorphous and crystalline regions in film-blown poly(ε-caprolactone)2000In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 41, no 4, p. 1297-1304Article in journal (Refereed)
  • 10. Gallet, G.
    et al.
    Carroccio, S.
    Rizzarelli, P.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Thermal degradation of poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer: comparative study by SEC/NMR, SEC/MALDI-TOF-MS and SPME/GC-MS2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 4, p. 1081-1094Article in journal (Refereed)
    Abstract [en]

    By comparing size exclusion chromatography/matrix assisted laser desorption ionisation (SEC/MALDI) and SEC/NMR spectra from virgin poly(ethylene oxide-propylene oxide-ethylene oxide) triblock copolymer, we were able to understand the bimodal distribution observed in poloxamer 407. Propylene oxide, isomerised to allyl alcohol during polymerisation, eventually forms a Poly(ethylene oxide-propylene oxide) diblock copolymer when EO is added to the feed. The oxidative thermal degradation of poloxamer 407 at 80 degreesC in air was studied. We found by MALDI that degradation starts after 21 days in the PPO block of the copolymer. This result was confirmed by solid phase microextraction/gas chromatography-mass spectrometry (SPME/GC-MS): The first volatile degradation product to appear is 1,2-propanediol,1-acetate,2-formate. The structure of this molecule suggests that a six-ring intramolecular decomposition reaction of the PPO chain occurs at the very beginning of the polymer breakdown. Thus, the secondary hydroperoxide formed on the PPO chain plays a major role on the thermoxidation of poloxamer materials.

  • 11. Gasslander, Ulla
    et al.
    Arbin, Astrid
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Polymer-water partition coefficients of extended range measured by using organic modifiers in the aqueous phase2007In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 48, no 26, p. 7523-7530Article in journal (Refereed)
    Abstract [en]

    A procedure for estimating equilibrium polymer-water partition coefficients over a broad range of solute hydrophobicity is presented and evaluated. The coefficients were calculated from the concentration change in the liquid phase and hydro-organic mixtures of varying proportions were used to extend the range. Three hydrophobic polymers (PP, PE, and EBA), two types of solvent (acetonitrile and alcohols) and 12 model solutes were used. The estimated polymer-water partition coefficients, log K-pw, ranged from -0.5 to 8.5. The coefficients correlated to other partitioning systems such as the calculated log Poctanol-water up to similar to 14 and the retention factor (log k(w)) in reversed-phase liquid chromatography.

  • 12.
    Glauser, T
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Johansson, M
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Hult, A
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Electron-beam curing of thick thermoset composite matrices1999In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 40, p. 5297-5302Article in journal (Refereed)
    Abstract [en]

    Electron-beam (EB) curing of two epoxy resins, one acrylated and one methacrylated, has been investigated. The change in thermomechanical properties, such as T-g, and the change of residual unsaturation have been studied as a function of dose. These results, in combination with in situ measurements of the temperature during cure, have shown the importance of sample geometry for the final properties of the thermoset. The thermal history of the sample during cure greatly affects the properties of the cured resin. (C) 1999 Elsevier Science Ltd. All rights reserved.

  • 13. Glauser, T
    et al.
    Johansson, Mats
    Hult, Anders
    Electron-beam curing of thick thermoset composite matrices1999In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 40Article in journal (Refereed)
  • 14.
    Hakkarainen, Minna
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Rapid (bio)degradation of polylactide by mixed culture of compost microorganisms - low molecular weight products and matrix changes2000In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 41, no 7, p. 2331-2338Article in journal (Refereed)
    Abstract [en]

    Poly(L-lactide) (PLLA) was rapidly (bio)degraded by a mixed culture of compost microorganisms. After 5 weeks in biotic environment, the films had fragmented to fine powder, while the films in corresponding abiotic medium still looked intact. Analysis of the low molecular weight products by GC-MS showed that microorganisms rapidly assimilated lactic acid and lactoyl lactic acid from the films. At the same time, a new degradation product, ethyl ester of lactoyl lactic acid was formed in the biotic environment. This product cannot be formed by abiotic hydrolysis and it was not detected in the abiotic medium. The degradation of the PLLA matrix was monitored by differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and scanning electron microscopy (SEM). A rapid molecular weight decrease and increasing polydispersity was observed in the biotic environment. In the abiotic environment only a slight molecular weight decrease was seen and the polydispersity started decreasing towards 2.0. This indicates different degradation mechanisms, i.e. preferred degradation near the chain ends in the biotic environment and a random hydrolysis of the ester bonds in the abiotic environment. SEM micrographs showed the formation of patterns and cracks on the surface of the films aged in biotic medium, while the surface of the sterile films remained smooth. The SEM micrographs showed a large number of bacteria and mycelium of fungi growing on the surface of the biotically aged films.

  • 15. Hassanzadeh, Salman
    et al.
    Feng, Zhaoxuan
    Pettersson, Torbjörn
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology.
    Hakkarainen, Minna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    A proof-of-concept for folate-conjugated and quercetin-anchored pluronic mixed micelles as molecularly modulated polymeric carriers for doxorubicin2015In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 74, p. 193-204Article in journal (Refereed)
    Abstract [en]

    Pluronic, F127 (PEG-PPO-PEG, Mn = 12,500 g/mol) and reverse pluronic, 10R5 (PPO-PEG-PPO, Mn = 2000 g/mol) were molecularly modulated to reach multifunctional mixed micelle systems aiming to overcome some of the inherent weaknesses of pluronic based drug delivery systems. Targeting function was introduced by covalent attachment of folic acid to F127 (F127-FA), while quercetin was anchored to 10R5 (P-Q). The successful syntheses were evidenced by H-1 NMR, FTIR, DSC and UV-Vis. The proof-of-concept for the mixed micelles prepared from the drug anchored pluronics was demonstrated through reduced CMCs, slower release rates and increased Doxorubicin (DOX) encapsulation capacity from similar to 19% to similar to 43%. Quercetin therefore boosted the interactions of DOX with the hydrophobic core of the micelles. This was further evidenced by colloidal probe AFM which demonstrated almost doubled adhesion forces between the DOX coated probe and the quercetin modified pluronic as compared to the plain pluronic. The pre-biological essay of the DOX-modulated mixed micelle demonstrates promising properties. In addition quercetin has previously been proposed as combinatory drug to DOX enhancing its therapeutic function and reducing the side effects to normal cells.

  • 16.
    Hedenqvist, Mikael S.
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Doghieri, F.
    The significance of the zero-concentration diffusivity value obtained from integral desorption data2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 1, p. 223-226Article in journal (Refereed)
    Abstract [en]

    n-Hexane zero-concentration diffusivity in high density polyethylene obtained 'indirectly' from integral desorption measurements using the free volume concept was compared with the zero-concentration diffusivity obtained directly at low-n-hexane activities using a quartz-ring system. The difference between the results obtained by the indirect and direct methods was within the experimental error. The concentration dependence of the diffusivity predicted by the Cohen-Turnll-Fujita free volume theory was in accordance with experimental data.

  • 17.
    Hedenqvist, Mikael S.
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Krook, M.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Two-stage sorption in rubbery semicrystalline polymers: transport of primary alcohols in polyesteramide2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 10, p. 3061-3068Article in journal (Refereed)
    Abstract [en]

    This paper deals with the two-stage sorption of methanol, 1-propanol and I-hexanol in a rubbery semicrystalline polyesteramide. This is the first time two-stage sorption is reported for a semicrystalline rubbery polymer. Mass uptake, specimen geometry and surface concentration were measured independently. The two-stage sorption curve describes two overlapping processes; a very rapid diffusion (mode 1) superimposed onto a normal s-shaped sorption curve (mode 2). Mode I swelling was uni-dimensional and mode 2 swelling was initially uni-dimensional and later three-dimensional. It was possible to model the sorption curves by assuming time-dependent solute-surface-concentration conditions, similar to those used to describe simple s-shaped sorption. The obtained time dependence, characterised by a single relaxation time, agreed with experimental values of the surface concentration obtained by infrared spectroscopy. The relaxation time increased exponentially with increasing size of the diffusing alcohol molecule. The solubility of the alcohols in the polymer increased with increasing hydroxyl-group density. The diffusivity of alcohol decreased nonlinearly with increasing length of the molecule, size effects being less important for larger solutes.

  • 18.
    Hedenqvist, Mikael S.
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Yousefi, Hamid Reza
    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.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Trollsas, M.
    Hedrick, J. L.
    Transport properties of hyperbranched and dendrimer-like star polymers2000In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 41, no 5, p. 1827-1840Article in journal (Refereed)
    Abstract [en]

    Moisture transport properties were assessed by sorption and desorption measurements on hydroxyl-functional hyperbranched polyesters based on 2,2-bis(methylol) propionic acid (bis-MPA) as AB(2)-monomer with ethoxylated pentaerythritol. A series of these polymers with different molar masses were studied. For the first time, it is reported that sigmoidal sorption curves were successfully modelled using a time-dependent surface boundary concentration, where the relaxation time was obtained from the mechanical stress relaxation data. The zero concentration diffusivities were very small and comparable with the values of fully amorphous poly(vinyl alcohol). Both the diffusivity data and the stress relaxation data indicated that these materials were plasticized by moisture. Ethylene glycol transport properties were measured on a hexadecanoate(C16)-terminated bis-MPA hyperbranched polymer. The replacement of the hydroxyl groups with C16 paraffin tails resulted in an increase in solute diffusivity despite the fact that these polymers became semicrystalline. The shape of the desorption curves indicated that continuous micropores were present and facilitated mass transport. The moisture transport properties were also measured on a series of semicrystalline dendrimer-like star poly(epsilon-caprolactone(s)). The low measured densities of these highly crystalline dendrimers confirmed that the porosity, as indicated by the shape of the desorption curves, had to be discontinuous. The porosity in the (C16)-terminated and the poly(epsilon-caprolactone(s)) was impossible to eliminate by applying a high external pressure during crystallization. A collective view of all the results obtained confirm that the transport properties are primarily controlled by the hydroxyl group concentration.

  • 19. Hillborg, H.
    et al.
    Ankner, J. F.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Smith, G. D.
    Yasuda, H. K.
    Wikstrom, K.
    Crosslinked polydimethylsiloxane exposed to oxygen plasma studied by neutron reflectometry and other surface specific techniques2000In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 41, no 18, p. 6851-6863Article in journal (Refereed)
    Abstract [en]

    Spin-coated specimens of crosslinked polydimethylsiloxane (PDMS) exposed to radio-frequency (RF) and microwave (MW) oxygen plasma were studied by specular neutron reflectometry, X-ray photoelectron spectroscopy (XPS), Wilhelmy balance, contact angle measurements, scanning electron microscopy and atomic force microscopy. Neutron reflectometry and XPS showed that the oxygen plasma led to the formation of a smooth (<10 nm), oxidised surface layer with a thickness of 130-160 nm. The oxidised layer contained a mixture of the original polymer and silicon bonded to three or four oxygen atoms (SiOx). The oxidised layer was thinner after longer plasma exposure, indicating a decrease in specific volume due to a conversion of the polymer structure to an inorganic SiOx-rich structure. The formation of the SiOx-containing layer with low segmental mobility was further confirmed by the small hysteresis in the Wilhelmy balance measurements. The similarity in the hydrophobicity recovery kinetics of specimens aged in dry air, dry argon and vacuum and XPS data showed that the hydrophobicity recovery is not due to contamination through adsorption from the atmosphere but due to migration of low molar mass PDMS species to the surface. Scanning electron microscopy also showed the presence of surface cracks in heavily oxidised specimens.

  • 20. Hillborg, H.
    et al.
    Karlsson, Sigbritt
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Characterisation of low molar mass siloxanes extracted from crosslinked polydimethylsiloxanes exposed to corona discharges2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 21, p. 8883-8889Article in journal (Refereed)
    Abstract [en]

    Crosslinked polydimethylsiloxanes were exposed to corona discharges in dry air at normal pressure. Short-time solvent extraction and subsequent analysis of the extractables, by gas chromatography, mass spectrometry and size exclusion chromatography showed that, oligomers consisting mainly of cyclics with 4-9 repeating units were formed during corona exposure. The size distribution of the oligomers was independent of the crosslink density and corona exposure time. The amount of oligomers located at the surface increased, with increasing storage time, after the corona exposure in qualitative agreement with the ongoing hydrophobic recovery process. Longer extractions penetrated deeper into the samples, and, in addition to the cyclic oligomers, higher molar mass species (similar to 50,000 g mol(-1) for unexposed samples) were detected. Samples exposed to corona, treated in this way, showed a broadening of the high molar mass peak towards lower molar masses.

  • 21. Hillborg, H.
    et al.
    Sandelin, M.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Hydrophobic recovery of polydimethylsiloxane after exposure to partial discharges as a function of crosslink density2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 17, p. 7349-7362Article in journal (Refereed)
    Abstract [en]

    Polydimethylsiloxanes with different crosslink densities were exposed to corona discharges or GHz air plasma and studied by contact angle measurements, X-ray photoelectron spectroscopy, optical microscopy, scanning electron microscopy and atomic force microscopy. The degree of surface oxidation increased with increasing exposure time with a limiting depth of 100-150 nm. Surface oxidation was faster in more highly crosslinked polymers. Within the oxidised layer, a brittle, microporous silica-like layer with a minimum organic silicone content of 40% gradually developed with increasing exposure time. The strain at which the silica-like layer cracked decreased with increasing dose of corona or air plasma. The hydrophobic recovery following the corona/air plasma exposure occurred at a slow rate by diffusion of oligomers through the microporous but uncracked silica-like layer or at a much higher rate by transport of oligomers through cracks in the silica-like layer.

  • 22. Hong, Y.
    et al.
    Coombs, S. J.
    Cooper-White, J. J.
    Mackay, M. E.
    Hawker, C. J.
    Malmström, Eva
    KTH, Superseded Departments, Polymer Technology.
    Rehnberg, N.
    Film blowing of linear low-density polyethylene blended with a novel hyperbranched polymer processing aid2000In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 41, no 21, p. 7705-7713Article in journal (Refereed)
    Abstract [en]

    The use of hyperbranched polymer (HBP) as a processing aid for linear low-density polyethylene (LLDPE) in the tubular film blowing process was investigated. Through the addition of HBP, sharkskin was successfully eliminated without significantly changing the overall physical properties of LLDPE films. Also, there was a minimum of 40% enhancement in processing rate with addition of 0.5 wt% HBP. The study showed that HBP and LLDPE are immiscible, and HBP has a tendency to migrate to the surface, subsequently, it seems to form a lubricating layer between the metal surfaces and the bulk material. This phase separation between HBP and LLDPE results in an HBP-rich surface, which has a high potential to create unique surface properties tailored to various applications. Rheological analysis indicated that excessive slip was present in HBP/LLDPE suggesting that the onset of slip is not the cause of sharkskin. On the contrary, it may be partially responsible for the elimination of sharkskin.

  • 23.
    Jonsson, Magnus
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nordin, Ove
    Malmström, Eva
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hammer, Claes
    Suspension polymerization of thermally expandable core/shell particles2006In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 47, no 10, p. 3315-3324Article in journal (Refereed)
    Abstract [en]

    Acrylonitrile (AN)-methacrylonitrile (MAN) copolymer particles with a core/shell structure were prepared by suspension polymerization. The particles were about 10–20 μm in diameter and had a hollow core containing an inert hydrocarbon. The influence of the monomer feed ratio and the polymerization temperature on the particle morphology was studied. One purpose of this study was to determine the boundaries for achieving a core/shell structure with the polymer encapsulating the hydrocarbon. When polymerizing at 62 °C, it was found that an initial AN/MAN feed ratio (fAN) between 0.15 and 0.9 results in core/shell particles with encapsulated hydrocarbon. fAN lower than 0.15 yielded solid particles with no hydrocarbon encapsulated while fAN higher than 0.9 yielded particles built up entirely from agglomerates of smaller primary particles. In contrast, when polymerizing at 80 °C, a much narrower span of fAN (0.5–0.85) yielded particles with hydrocarbon encapsulated. The influence on monomer conversion and the molecular weight of the polymer was also studied.

  • 24.
    Karlsson, Gunder E.
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Molecular dynamics simulation of oxygen diffusion in dry and water-containing poly(vinyl alcohol)2004In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 45, no 11, p. 3893-3900Article in journal (Refereed)
    Abstract [en]

    The kinetics and mechanisms of diffusion of oxygen and water in dry and water-containing amorphous syndiotactic poly(vinyl alcohol) were studied at 502 K and normal pressure by molecular dynamics simulation. Penetrant molecule trajectories were obtained in a system with 600 repeating units of poly(vinyl alcohol) and 0, 40 (2.6 wt%) and 80 (5.2 wt%) water molecules. Under dry conditions, oxygen molecules jumped in a cage-like fashion. The oxygen molecule diffused in a liquid-like fashion while water diffusion was cage-like in the system with 5.2 wt% water. The hydrogen bond lifetimes among the water molecules were significantly shorter than those formed between water and the polymer and between different polymer segments. The hydrogen bond lifetimes among all species were, within experimental error, unaffected by the content of water, even though the oxygen diffusivity increased exponentially and the water diffusivity increased to some extent with increasing water content. It seemed that the diffusivity was sensitive primarily to the decrease in concentration of polymer-polymer hydrogen bonds. which followed from the increase in water content. This finding was consonant with the analysis of the oxygen molecule motion relative to the nearest polymer backbone, which revealed that it jumped preferentially along the polymer chain and towards the backbone. This behavior was more pronounced when the dynamics were analyzed over longer distances (5 Angstrom) and it was less pronounced in the water-rich systems. The simulations indicated that water clustering was absent and consequently that water was homogeneously distributed in the polymer systems.

  • 25. Kassa, Hailu G.
    et al.
    Stuyver, Johan
    Bons, Anton-Jan
    Haviland, David B.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Thorén, Per-Anders
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Borgani, Riccardo
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics.
    Forchheimer, Daniel
    KTH, School of Engineering Sciences (SCI), Applied Physics, Nanostructure Physics. Intermodulation Products AB, Landavägen, 4193, Segersta, Sweden.
    Leclere, Philippe
    Nano-mechanical properties of interphases in dynamically vulcanized thermoplastic alloy2018In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 135, p. 348-354Article in journal (Refereed)
    Abstract [en]

    We present a high-resolution study of the viscoelastic response of a thermoplastic alloy using a multi-frequency method called intermodulation atomic force microscopy. We quantitatively characterize the response in terms of calibrated dynamic force quadrature curves, showing the conservative and dissipative forces at each image pixel as functions of the oscillation amplitude for industrial polymer blends. 

  • 26. Kim, Young Yong
    et al.
    Kim, Kyungtae
    Jung, Sungmin
    Kim, Changsub
    Kim, Jehan
    Roth, Stephan V.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Sprung, Michael
    Vartanyants, Ivan A.
    Ree, Moonhor
    Synchrotron X-ray scattering and photon correlation spectroscopy studies on thin film morphology details and structural changes of an amorphous-crystalline brush diblock copolymer2016In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 105, p. 472-486Article in journal (Refereed)
    Abstract [en]

    We investigated structural details and temperature-induced structural changes of an amorphous-crystalline brush diblock copolymer, poly(3-((6-((7-(9H-carbazol-9-yl)heptanoyl)oxy)hexyl)thio)propylglycidyl ether)(60)-b-poly(glycidyl 12-((3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl)oxy)-12oxododecanoate)(20) (PGK(60)-PGF(20)) in nanoscale thin films using synchrotron grazing incidence X-ray scattering (GIXS) and X-ray photon correlation spectroscopy (XPCS). Interestingly, the diblock copolymer was found to form a mixture of two different hexagonal cylinder structures (HEX1 and HEX2) where the PGF cylinders were aligned in the film plane. HEX1 was composed of PGF cylinders with higher population of crystals while HEX2 consisted of PGF cylinders with lower population of crystals. Surprisingly, the PGF block chains favorably self-assembled because of strong lateral interactions in the bristles, forming vertical multibilayer structure with partial interdigitation even in the highly confined cylindrical geometry. In heating run up to 340 K, some fraction of HEX2 was transformed to HEX1 via cold crystallization. In contrast, HEX1 was transformed to HEX2 above 340 K because of melting of the PGF crystals. The XPCS analysis found that the HEX structural changes associated with the cold crystallization in the PGF cylinder domains took place with relatively fast dynamics. The HEX structural changes associated with melting of the PGF crystals in the cylinder domains occurred with relatively slow dynamics; this unusual dynamics of structural changes might be attributed to a high energy melting process of PGF crystals against strong lateral interactions of the bristles.

  • 27. Kornmann, X.
    et al.
    Lindberg, H.
    Berglund, Lars A.
    Synthesis of epoxy-clay nanocomposites: influence of the nature of the clay on structure2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 4, p. 1303-1310Article in journal (Refereed)
    Abstract [en]

    Epoxy-clay nanocomposites were synthesised using two montmorillonite clays (MMT) with different cation-exchange capacities (CEC) (94 and 140 meg/100 g). The purpose was to investigate the influence of the CEC of the clay on the synthesis and structure of epoxy-clay nanocomposites. The dispersion of the 1 nm thick clay layers was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Although XRD data did not show any apparent order of the clay layers in the nanocomposite, TEM revealed parallel clay layers with interlamellar spacing of 90 Angstrom (MMT of high CEC) and 110 Angstrom (MMT of lower CEC) and the presence of remnant multiplets of non-exfoliated layers. A mechanism responsible for the influence of CEC on nanocomposite interlamellar spacing is discussed. The dispersion of the clay was investigated by SEM and found to be finer in the nanocomposites as compared with in conventional composites although the nanocomposites still have clay aggregates at the microscale rather than a monolithic structure.

  • 28. Kornmann, X.
    et al.
    Lindberg, H.
    Berglund, Lars A.
    Synthesis of epoxy-clay nanocomposites. Influence of the nature of the curing agent on structure2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 10, p. 4493-4499Article in journal (Refereed)
    Abstract [en]

    Epoxy-clay nanocomposites were synthesised by swelling an organophilic montmorillonite in a diglycidyl ether of bisphenol A resin with subsequent polymerisation. Three different curing agents were used: an aliphatic diamine and two cycloaliphatic diamines. The cure kinetics of these systems was evaluated by differential scanning calorimetry and the structure of the nanocomposites was characterised by X-ray diffraction and transmission electron microscopy. Successful nanocomposite synthesis was dependent not only on the cure kinetics of the epoxy system but also on the rate of diffusion of the curing agent into the galleries because it affects the intragallery cure kinetics. The nature of the curing agent influences these two phenomena substantially and therefore the resulting structure of the nanocomposite. The curing temperature controls the balance between the extragallery reaction rate of the epoxy system and the diffusion rate of the curing agent into the galleries. Thus, the choice of curing agent and curing conditions controls the extent of exfoliation of the clay in the material.

  • 29.
    Laihonen, Sari J.
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Werner, P.-E.
    Martinez-Salazar, J.
    Crystallization kinetics and morphology of poly(propylene-stat-ethylene) fractions.1997In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 38, no 2, p. 361-369Article in journal (Refereed)
    Abstract [en]

    The crystallization and melting behaviour and the morphology of fractions of poly(propylene-stat-ethylene) with 2.7–11.0 mol% ethylene were studied by differential scanning calorimetry, wide-angle X-ray scattering, polarized light microscopy and transmission electron microscopy, after etching with permanganic acid. The inclusion of ethylene co-repeating units in isotactic polypropylene (0–11.0 mol% ethylene) caused approximately linear decreases in kinetic and equilibrium melting temperatures and in the glass transition temperature with increasing ethylene content. X-ray scattering showed that the content of the γ form increased with increasing ethylene content, increasing crystallization temperature and decreasing cooling rate from the molten state. It was shown for one of the copolymers (8.7 mol% ethylene) that during heating approximately 50% of the γ form was converted to the α form before the final melting of the sample. The rest of the γ crystals melted without transformation to the α form. The multimodality of the crystal melting above the crystallization temperature in the polymers with a more uniform crystal structure was caused by recrystallization during heating, whereas polymers with appreciable contents of both α and γ forms exhibited multimodal melting at all the heating rates adopted. The size of the low temperature melting peak as assessed at a heating rate of 40 K min−1 was approximately proportional to the initial content of the γ form. By comparison with the spherulitic structure of homopolymers, that of the copolymers was coarser with internal and peripheral pockets of molten material during spherulite growth. The crystal lamellae exhibited more curvature in the copolymer samples than in the homopolymer.

  • 30.
    Laihonen, Sari J.
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Werner, P.-E.
    Westdahl, M.
    Martinez-Salazar, J.
    Crystal structure and morphology of melt-crystallized poly(propylene-stat-ethylene) fractions.1997In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 38, no 2, p. 371-377Article in journal (Refereed)
    Abstract [en]

    Crystallinity, crystal structure and lamellar thickness in melt-crystallized samples of poly(propylene-stat-ethylene) fractions with 2.7–11.0 mol% ethylene comonomer and of approximately constant tacticity were assessed by wide- and small-angle X-ray scattering, differential scanning calorimetry and infra-red spectroscopy. Most of the samples were crystallized under isothermal conditions at 373 K. In comparison with an isotactic homopolymer of polypropylene, the copolymers showed lower crystallinity, melting enthalpy and average length of 3/1 helices, a slightly larger unit cell, a longer long period and an invariant lamellar thickness. The X-ray crystallinity of the copolymers remained approximately constant with increasing ethylene content, whereas the γ-crystallinity increased and the heat of fusion decreased moderately. It is suggested that the ethylene units are partially included in the crystals, and that this causes the invariance in crystallinity and crystal thickness. The observed gradual decrease in average 3/1 helix length with increasing ethylene content as assessed by infra-red spectroscopy is in accordance with this suggestion.

  • 31.
    Lange, J
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Johansson, M
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Coating Technology.
    Kelly, C T
    Halley, P J
    Gelation behaviour during chainwise crosslinking polymerisation of methacrylate resins1999In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 40, p. 5699-5707Article in journal (Refereed)
    Abstract [en]

    The gelation process in chainwise crosslinking polymerisation of methacrylate resins with average functionalities of 2.1-50 (1.05-25 methacrylate groups/molecule) was investigated using dynamic mechanical analysis. For all systems a crossover in tan delta (tan delta independent of frequency) was observed at gelation. The gel time was found to decrease with increasing functionality of the system. Within the measured frequency ranges, power law behaviour for the dynamic modulus was observed at the gel point in all systems. A value of the power law exponent n of 0.4 +/- 0.2 to 0.6 +/- 0.1 (increasing with increasing functionality of the system) was determined for gelation during reactions at T greater than or equal to T-g infinity. This trend suggests that the differences in screening between the systems dominate over the difference in fractal dimension. For reaction temperatures below T-g infinity a value of n = 0.3 +/- 01 was obtained, which was attributed to the influence of micro-vitrification. (C) 1999 Elsevier Science Ltd. All rights reserved.

  • 32. Lange, J.
    et al.
    Stenroos, E.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    Malmström, Eva
    KTH, Superseded Departments, Polymer Technology.
    Barrier coatings for flexible packaging based on hyperbranched resins2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 17, p. 7403-7410Article in journal (Refereed)
    Abstract [en]

    Hyperbranched resins have been evaluated for use as barrier coatings. Different types of modified hydroxy-functional hyperbranched polyester resins were prepared and partially end-capped with acrylate or methacrylate units. Crystalline end-groups (poly(epsilon -caprolactone) were grafted onto some resins. The coatings were applied on poly(ethylene terephthalate) and polypropylene substrates and crosslinked by UV light and their barrier against oxygen and water vapour determined. The results show that hyperbranched coatings give a pronounced improvement in oxygen barrier on both substrates. Expressed in terms of oxygen permeability coefficient, the improvement was a factor of up to 60 times compared to polypropylene and up to 2.2 times compared to poly(ethylene terephthalate). As for other hydroxy-functional barrier polymers, the amount of hydroxyl groups in the hyperbranched resins was found to play a major role concerning the oxygen barrier, controlling both performance and water sensitivity. It was seen that humidity led to a decrease in barrier at the highest hydroxyl group concentration, whereas the barrier performance of coatings with lower concentration of hydroxyl groups instead improved under humid conditions. It was also found that crystalline end-groups did not improve the oxygen barrier and that none of the synthesised resins gave any improvement in water vapour barrier.

  • 33. Lange, J.
    et al.
    Toll, Staffan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
    Månson, J. -AE.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Residual stress build-up in thermoset films cured above their ultimate glass transition temperature1995In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 36, no 16, p. 3135-3141Article in journal (Refereed)
    Abstract [en]

    The build-up of in-plane stress over time during curing and on cooling of thermoset films is investigated. The stress in a thin contracting film on a rigid substrate is analysed, and obtained as an integral of essentially the shear modulus and thickness of the curing film. Films are cured and cooled between parallel plates in a dynamic torsional rheometer, which allows dynamic shear modulus and film thickness to be monitored simultaneously. Stress predictions are compared with independent stress observations, obtained using a bilayer beam bending technique. A conventional epoxy system and a low molar mass difunctional acrylate are studied and compared. The epoxy, in agreement with the literature, exhibits no detectable stress during the curing reaction, nor during cooling to the glass transition temperature (Tg), but develops stress on cooling below Tg. The acrylate, by contrast, generates considerable stress throughout the reaction and cooling, with the major part of the stress originating above Tg. The observed stress build-up agrees well with the theoretical calculations based on the time-evolution of shear modulus and film thickness. Finally, approximate formulae for the estimation of residual stress are given. It is shown how the overall residual stress, as well as the contributions from the different parts of the cure process in a wide variety of systems, can be estimated from the mechanical and thermal properties of the polymer and the substrate.

  • 34. Lindberg, T.
    et al.
    Wirsen, A.
    Albertsson, Ann-Christine
    KTH, Superseded Departments, Polymer Technology.
    Graft polymerisation of acrylamide onto PCL film by electron beam pre-irradiation in air or argon. Morphology in the final grafted state2000In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 41, no 11, p. 4099-4111Article in journal (Refereed)
    Abstract [en]

    Poly(epsilon-caprolactone) has been graft polymerised to final graft yields with acrylamide (AAm) as monomer in an aqueous solution by the pre-irradiation method. The synthesis of the samples obtained, pre-irradiated in air or argon atmosphere, was controlled by dose and concentration of inhibitor, provided as Mohr's salt, in the ranges from 2.5 to 10 Mrad and from 0.005 to 0.500 wt%, respectively. Final graft yields and lateral dimensions in swollen condition ranged from 70 to 3400 wt%, and from 23 x 30 to 89 x 94 mm(2), respectively, as atmosphere during irradiation, dose and concentration of inhibitor were altered. These properties gave values in crystallinity extending from 4 to 57 wt%. Samples pre-irradiated in air and subsequently graft polymerised yielded higher values of crystallinity in the entire range of dose and concentration of inhibitor. At low concentration of inhibitor, final graft yield and lateral dimension for samples pre-irradiated in air had considerably larger values while the final graft yield and lateral dimension of samples pre-irradiated in argon had slightly larger values at high concentration of inhibitor. The initial biaxial morphology of the PCL film was continuously transformed into a uniform morphology, which was reached at a final graft yield of approximately 800 wt%.

  • 35. Liu, X. H.
    et al.
    Wu, Q. J.
    Berglund, Lars A.
    Polymorphism in polyamide 66/clay nanocomposites2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 18, p. 4967-4972Article in journal (Refereed)
    Abstract [en]

    Polyamide 66/clay nanocomposites (PA66CN) were prepared via melt compounding method by using a new kind of organophilic clay, which was obtained through co-intercalation of epoxy resin and quaternary ammonium into Na-montmorillorlite. The silicate layers were dispersed homogeneously and nearly exfoliated in polyamide 66 (PA66) matrix. The introduction of silicate layers induced the appearance of the gamma phase in PA66CN at room temperature, more clay loadings would amplify this phenomenon; the addition of clay also changed the structure of the a crystalline phase. The presence of silicate layers increased the crystallization rate and had a strong hetero phase nucleation effect on PA66 matrix. The lower Brill transition temperature of PA66CN can be attributed to the strong interaction between polyamide chains and surfaces of silicate layers.

  • 36. Liu, X. H.
    et al.
    Wu, Q. J.
    Berglund, Lars A.
    Fan, J. Q.
    Qi, Z. N.
    Polyamide 6-clay nanocompositles/polypropylene-grafted-maleic anhydride alloys2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 19, p. 8235-8239Article in journal (Refereed)
    Abstract [en]

    Polyamide 6-clay nanocomposites (PA6CN) based on montmorillonite typically show some brittleness with clay addition. In order to address this problem, PA6CN/PP-g-MAH alloys were prepared through blending PA6CN with polypropylene-grafted-maleic anhydride (PP-g-MAH). The mechanical properties, dynamic mechanical temperature spectra, morphology and water absorption of the alloys were studied. Compared with PA6CN, the notched impact strength of the alloys increased greatly while the alloys still maintained higher stiffness and strength than that of PA 6. The morphological studies via scanning electron microscopy (SEM) showed a PP-g-MAH toughen phase dispersed in PA6CN matrix. As the PP-g-MAH content was increased, reduced water absorption was observed.

  • 37.
    Magnusson, Helene
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Malmström, Eva
    KTH, Superseded Departments, Polymer Technology.
    Hult, Anders
    KTH, Superseded Departments, Polymer Technology.
    Johansson, Mats K. G.
    KTH, Superseded Departments, Polymer Technology.
    The effect of degree of branching on the rheological and thermal properties of hyperbranched aliphatic polyethers2002In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 43, no 2, p. 301-306Article in journal (Refereed)
    Abstract [en]

    A series of hyperbranched aliphatic polyethers with different degree of branching (DB) and molecular weights have been studied with respect to their rheological and thermal properties. The DB was shown to affect the ability of the polymers to crystallize and thereby also the rheological properties of the polymers. A low DB resulted in semi-crystalline polymers with melting points between 100 and 130 degreesC. The polymers with a higher DB were essentially amorphous and behaved as non-entangled Newtonian liquids in the molten state.

  • 38. Marklund, E.
    et al.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Wiberg, G.
    Properties of polyketone/polypropylene blends2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 7, p. 3153-3160Article in journal (Refereed)
    Abstract [en]

    Blends of polypropylene and two polyketone grades with low and medium-high viscosities were prepared by melt extrusion. To obtain good compatibility, a maleic-anhydride-polypropylene copolymer was added to the blends. Polyoxypropylenediamine was added to some of the blends to further enhance compatibility. The blends were analysed with differential scanning calorimetry. In a second step, the blends were compression or injection moulded. Scanning electron microscopy, shear viscosity, density measurements and infrared spectroscopy were used to characterise the moulded blends and their oxygen permeabilities were assessed. Impact strength and hardness were measured on injection-moulded blends. It was shown that the oxygen barrier properties of polypropylene could be greatly enhanced by a small addition of primarily the low-viscosity polyketone. A content of 23.9% by volume of polyketone was sufficient to lower the permeability by 70% compared to pure polypropylene. This was because a polyketone-rich surface layer was formed during compression moulding. The incorporation of polyoxypropylenediamine had a profound effect on the morphology. The polyketone particles in this case were very small, and the absence of pull-outs suggested an enhanced phase adhesion between the different components. Further, the incorporation of polyoxypropylenediamine had no impact on the oxygen permeability but the impact roughness and hardness were increased and the shear viscosity was also increased in its presence. This indicated that chemical bonds were formed between polyketone, polyoxypropylenediamine and the maleic-anhydride-polypropylene copolymer. This network suppressed crystallisation of primarily the polyketone component.

  • 39.
    Mattozzi, Alessandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Minelli, M
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Computer-built polyethylene spherulites for mesoscopic Monte Carlo simulation of penetrant diffusion:  influence of crystal widening and thickening2007In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 48, no 8, p. 2453-2459Article in journal (Refereed)
    Abstract [en]

    An algorithm able to mimic crystal lengthening, branching, widening and thickening was developed in order to build spherulites similar to those observed in polyethylene. The ranges of volume crystallinity and crystal width-to-thickness ratio attainable were <= 40% and 8-35, respectively. An on-lattice Monte Carlo-based algorithm was used to generate penetrant trajectories in the built spherulites. Diffusivity was assessed from the mean-square displacement of the penetrant molecules, normalized with respect to the mean-square displacement of the penetrant molecules in a crystal-free system, and compared with the geometrical impedance factor calculated from the Fricke theory using morphological data samples in the simulated spherulites. The crystal blocking effect was greater in the tangential plane than along the spherulite radius. All data, except that for the highest crystallinity system (40%), conformed to a linear relationship between the geometrical impedance factor obtained from the diffusivity data and the geometrical impedance factor calculated from morphological data; the latter being calculated according to the Fricke model using averages based on the squares of the crystal width-to-thickness ratio data. This finding suggests that wide crystals had a more pronounced effect on the geometrical impedance factor than was indicated by their number fraction weight. The system with the highest volume crystallinity (40%) showed a markedly higher geometrical impedance factor than predicted by the Fricke theory using the two aforementioned modifications.

  • 40.
    Mattozzi, Alessandro
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Neway, Bereket
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Morphological interpretation of n-hexane diffusion in polyethylene2005In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 46, p. 929-938Article in journal (Refereed)
    Abstract [en]

    The diffusion of small-molecule penetrants in polyethylene is retarded by the detour caused by the crystals and by the segmental constraints imposed by the crystals on the penetrable phase. The earlier reported n-hexane diffusivity data for a series of homogeneous poly(ethylene-co-octene)s showed unexpectedly that the detour was greatest in the low crystallinity polymers. The crystal width-to-thickness ratio and the crystallinity were assessed by electron microscopy and differential scanning calorimetry and used in the Fricke model. The calculations showed that the geometrical impedance factor followed the same trend with increasing crystallinity as the data obtained from n-hexane desorption. The high geometrical impedance factor shown by the low crystallinity samples was due to the presence of crystals with an unusually high crystal width-to-thickness ratio. A unified relationship, including data for both linear and branched polyethylene was found between the fractional free volume and the phase composition of the penetrable phase including the liquid-like, interfacial liquid and the interfacial crystal core.

  • 41. Molochnikov, L. S.
    et al.
    Kovalyova, E. G.
    Zagorodni, A. A.
    Muhammed, Mamoun
    KTH, Superseded Departments, Materials Science and Engineering.
    Sultanov, Y. M.
    Efendiev, A. A.
    Coordination of Cu(II) and Ni(II) in polymers imprinted so as to optimize amine chelate formation2003In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 44, no 17, p. 4805-4815Article in journal (Refereed)
    Abstract [en]

    Molecular imprinting has become an established technique. However, little was done on direct investigation of the sorbents produced. In the present work, en ESR method was used for the investigation of the complex formation processes within the sorbents imprinted with copper(II) and nickel(II). The sorbents were synthesized from a mixture of linear low molecular weight polyethyleneimine oligomers. The composition, structure and distribution of complexes in the resin phase were investigated. The effects of the synthesis conditions, loading degree and water content were examined. The presence of certain copper complexes was found to be a convenient characteristic of the imprinting efficiency. The optimum synthesis conditions for obtaining sorbents imprinted with copper(II) or nickel(II) were identified. The imprinting results in the improvement of the stability of the complexes and the selectivity and working capacity of the sorbents. The imprinted samples are also characterized by a more even distribution of chelating sites. The synthesis conditions and loading by ions allow for the regulation of the ratio between individual complexes and magnetic associates in the resin phase. This is a critical point on the future use of the metal containing imprinted sorbents as catalysts.

  • 42.
    Moyassari, Ali
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Mostafavi, Hakhamanesh
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Columbia University, United States.
    Gkourmpis, T.
    Hedenqvist, Mikael S.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Nilsson, Fritjof
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Simulation of semi-crystalline polyethylene: Effect of short-chain branching on tie chains and trapped entanglements2015In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 72, p. 177-184Article in journal (Refereed)
    Abstract [en]

    A Monte-Carlo simulation method for assessing the tie chain and trapped entanglement concentration in linear polyethylene was extended to enable the simulation of explicitly branched polyethylene. A subroutine was added to the model making possible the incorporation of different branch lengths and distributions. In addition, the microstructure of branched polyethylene was considered to be made of lamellar stacks of different thicknesses, acknowledging the segregation phenomenon during crystallization. Also, based on complete exclusion of bulky branches from the crystal lattice, a 'pull-out' mechanism was developed for the relaxation of branched parts of polyethylene chains in the vicinity of the crystal layer. Simulations of two series of real polyethylene samples showed the effect of short-chain branching on the concentrations of tie chains and trapped entanglements. Introducing a few branches to an unbranched polyethylene increased the concentration of inter-lamellar connections significantly. This effect decayed if the number of branches was further increased. The tracking of the position of all the carbon atoms during the crystallization process was implemented in the model, making the average square end-to-end distance < r(2) > of polyethylene chains calculable. Simulation of chains with the same molar mass but with different branch contents showed a reduction in the average end-to-end distance with increased branching. The use of real molar mass distribution data was also added to the model features.

  • 43.
    Målberg, Sofia
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Finne Wistrand, Anna
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    The environmental influence in enzymatic polymerization of aliphatic polyesters in bulk and aqueous mini-emulsion2010In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 51, no 23, p. 5318-5322Article in journal (Refereed)
    Abstract [en]

    The catalytic effect of enzymes in different environments has been compared. Biodegradable polyesters and corresponding nanoparticles have been synthesized by an "eco-friendly" technique; enzyme-catalyzed ring-opening polymerization of lactones in bulk and in an aqueous mini-emulsion. Lipases from Burkholderia cepacia (lipase PS), B. cepacia immobilized on ceramic, Pseudomonas fluorescens and Candida Antarctica have been used as catalysts in the polymerization of L-Lactide (LLA), pentadecanolide (PDL) and hexadecanolide (HDL). The reaction conditions during the bulk polymerization of LLA were varied by adding different amounts of ethylene glycol at 100 degrees C or 125 degrees C. A number average molecular weight (M-n) of 78,100 was obtained when lipase PS was used at 125 degrees C. Lipase PS had a high catalytic activity in an aqueous environment with 100% conversion in 4 h, and the nanoparticles obtained from mini-emulsion polymerization were between 113 and 534 nm in size. The amount of hydrophobe affected the size of the PDL nanoparticles produced, less than the amount of surfactant in both systems.

  • 44. Neway, B.
    et al.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Effect of thermal history on free volume and transport properties of high molar mass polyethylene2003In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 44, no 14, p. 4003-4009Article in journal (Refereed)
    Abstract [en]

    The desorption of n-hexane from high molar mass polyethylene at 298 K has been studied. The polymer was given different thermal treatments to obtain differences in crystallinity, morphology and composition of the non-crystalline fraction. Crystal contents determined by Raman spectroscopy were always lower than those determined by density measurements. The systems with high crystallinity showed in relative terms a low content of interfacial component. The n-hexane solubilities of the samples were strictly proportional to the volume fraction of penetrable polymer (liquid-like and interfacial components) and the solubility was low in comparison with that of branched polyethylene of the same crystallinity. The Cohen-Tumbull-Fujita free volume theory was numerically capable of describing the desorption process in the polyethylenes studied. One of the methods used assumed that all three non-crystalline components-liquid-like, interfacial liquid-like and interfacial crystal core components-are penetrable by n-hexane and this method yielded data for the geometrical impedance factor and the fractional free volume with physically realistic trends, but the changes in the geometrical impedance factor was not in quantitative agreement with the Fricke model applied to the morphological data. This lack of numerical agreement is tentatively due to the fact that the assessment of crystal shape by transmission electron microscopy of stained sections systematically underestimates the crystal widths, particularly for the low-crystallinity samples with curved and 'twisting' crystal lamellae.

  • 45. Neway, B.
    et al.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Mathot, V. B. F.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Free volume and transport properties of heterogeneous poly(ethylene-co-octene)s2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 12, p. 5307-5319Article in journal (Refereed)
    Abstract [en]

    n-Hexane desorption measurements were pet-formed on heterogeneous poly(ethylene-co-octene)s with hexyl branch contents between 0.8 and 3.9 mol% and crystallinities between 30 and 60%, Crystal core contents obtained by Raman spectroscopy were lower than the density-based crystallinity, particularly For the samples with the highest degree of branching. A modified Cohen-Tumbull-Fujita free volume model adequately described the diffusivity data. The free volume of the penetrable phases was strongly dependent on their total volume fraction, suggesting the presence of an interfacial penetrable component with low fractional free volume. The dependence of the fractional free volume of the penetrable phases on the phase composition suggests that mass transport takes place from the liquid-like component to the interfacial component and that the penetrant molecules are trapped at the interfacial sites. The decrease in geometrical impedance factor with increasing crystallinity may be explained by the presence of extraordinarily wide dominant crystal lamellae in the heterogeneous low crystallinity samples. The saturation concentration of n-hexane in a wide range of polyethylenes (including the heterogeneous poly(ethylene-co-octene)s, linear polyethylenes and poly(ethylene-co-butene)s reported earlier; crystallinity range: 30-94%) showed a complex non-linear dependence on crystallinity that was qualitative in accordance with rubber elasticity theory considering also molecular cilia.

  • 46.
    Neway, Bereket
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Westberg, Åsa
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Mattozzi, Alessandro
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Hedenqvist, Mikael S.
    KTH, Superseded Departments, Polymer Technology.
    Baschetti, M. G.
    Mathot, V. B. F.
    Gedde, Ulf W.
    KTH, Superseded Departments, Polymer Technology.
    Free volume and transport properties of homogeneous poly (ethylene-co-octene)s2004In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 45, no 11, p. 3913-3922Article in journal (Refereed)
    Abstract [en]

    Liquid and vapour n-hexane sorption/desorption were studied on homogeneous poly(ethylene-co-octene)s produced by metallocene-catalyzed polymerisation covering a crystallinity range from 3.5 to 72.4%. Crystal core contents determined by Raman spectroscopy were lower than those determined by density assessments, particularly at low degrees of crystallinity. The solubility showed deviation from Henry's law. The solubilities of n-hexane in the homogeneous copolymers depended in a non-linear manner on the content of penetrable polymer component and were lower than those earlier reported for heterogeneous copolymers at the same contents of penetrable component. The concentration dependence of the thermodynamic diffusivity predicted by the Cohen-Turnbull-Fujita free volume theory was confirmed by the data obtained by the differential method and the differences between the results obtained from the integral and differential methods were within the margins of experimental error. The fractional free Volume of the penetrable polymer fraction increased with increasing fraction of penetrable polymer and with relative proportion of liquid-like component in the penetrable polymer fraction. The homogeneous copolymers showed a decreasing trend in the geometrical impedance factor with increasing degree of crystallinity.

  • 47.
    Nilsson, Fritjof
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Lan, X.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gkourmpis, T.
    Borealis.
    Hedenqvist, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymeric Materials.
    Gedde, Ulf
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Modelling tie-chains and trapped entanglements in polyethylene2012In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 53, no 16, p. 3594-3601Article in journal (Refereed)
    Abstract [en]

    A Monte Carlo random walk model was developed to simulate the chain structure of amorphous layers in polyethylene. The chains emerging from the orthorhombic crystal lamellae were either folding back tightly (adjacent re-entry) or performing a random walk (obeying phantom chain statistics) forming statistical loops or tie chains. A correct amorphous density (ca. 85% of the crystalline density) was obtained by controlling the probability of tight folding. Important properties like fracture toughness depend on the number of chains covalently linking together the crystalline regions. The model structure was analysed with a novel numerical topology algorithm for calculating the concentration of tie chains and trapped entanglements. The numerical efficiency of the algorithm allowed molecular cubic systems with a side length of 100 nm to be readily analysed on a modern personal computer. Simulations showed that the concentration of trapped entanglements was larger than the concentration of tie chains and that the thickness of the amorphous layer (L a) had a greater impact than the crystal thickness (L c) on the tie-chain concentration. In several other commonly used models, such as the Huang-Brown model, the influence of trapped entanglements and the effect of the L a/L c ratio are neglected. Simulations using as input the morphology data from Patel generated results in agreement with experimental rubber modulus data.

  • 48.
    Núñez, Eugenia
    et al.
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Ferrando, Carolina
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Malmström, Eva
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Claesson, Hans
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Werner, P. -E
    Gedde, Ulf
    KTH, Superseded Departments, Fibre and Polymer Technology.
    Crystal structure, melting behaviour and equilibrium melting point of star polyesters with crystallisable poly(ε–caprolactone) arms2004In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 45, no 15, p. 5251-5263Article in journal (Refereed)
    Abstract [en]

    Star polymers consisting of poly(ε-caprolactone), PCL, attached to third generation dendrimer, hyperbranched and dendron cores have been studied by differential scanning calorimetry and wide-angle X-ray scattering. The degree of polymerisation of the PCL arms of the star polymers ranged from 14 to 81. The crystal unit cell was the same for the star polymers as for their linear PCL analogues. The star polymers showed a lower degree of crystallinity than the linear PCL, suggesting that the dendritic cores imposed restriction on PCL crystallisation. Slow heating of rapidly cooled samples led to crystal rearrangement - a gradual increase in melting point with decreasing heating rate and recrystallisation followed by additional high temperature melting. The tendency for crystal rearrangement was less pronounced in star polymers based on dendrimer or hyperbranched cores, suggesting that the dendritic cores constitute an obstacle to crystal rearrangement. The star polymers showed higher equilibrium melting points than the linear PCL analogues. It is suggested that covalent attachment of the PCL arms to the dendritic core reduced the positional freedom and the entropy of the melt with respect to that of linear PCL.

  • 49.
    Núñez, Eugenia
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Gedde, Ulf W.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Single crystal morphology of star polyesters with crystallisable poly(ε–caprolactone) arms2005In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 46, no 16, p. 5992-6000Article in journal (Refereed)
    Abstract [en]

    Star-branched polymers consisting of poly(epsilon-caprolactone) (PCL) attached to third generation dendrimer, hyperbranched and dendron cores have been studied together with linear PCL analogues. The degree of polymerisation of the PCL arms of the star-branched polymers ranged from 14 to 81. Single crystals were grown from dilute solution and studied by transmission electron microscopy. Single crystals of linear PCL were multilayer hexagons with flat or slightly curved {110} and {100} faces. These single crystals were larger along [010] than along [100]. Single crystals of star-branched PCL showed the same basic shape, but with many crystallographic and irregular steps on the lateral crystal faces. The width of the micro-faces was typically 100-300 nm. These single crystals were more extended along [100] than along [010]. It is proposed that the high fold surface free energy and the constrained character of the star-branched polymers favour the formation of steps on the growth faces. Globular polycrystalline aggregates were also observed. They originated from a more concentrated polymer phase following phase separation of the solution. In the case of the star-branched polymers, lamellar branching was observed with a 30 angle between the crystals arms.

  • 50.
    Olabarrieta, Idoia
    et al.
    KTH, Superseded Departments, Polymer Technology.
    Forsström, Dan
    KTH, Superseded Departments, Polymer Technology.
    Gedde, Ulf
    KTH, Superseded Departments, Polymer Technology.
    Hedenqvist, Mikael
    KTH, Superseded Departments, Polymer Technology.
    Transport properties of chitosan and whey blended with poly(ε-caprolactone) assessed by standard permeability measurements and microcalorimetry2001In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 42, no 9, p. 4401-4408Article in journal (Refereed)
    Abstract [en]

    Blends of poly(p-caprolactone) (PCL) with chitosan and a whey-protein-isolate (WPI) were prepared by solution mixing and film casting. The purpose was to increase the water vapour resistivity of chitosan and whey by blending them with a hydrophobic biodegradable polymer. The water vapour transmission rate was determined by a standard technique and by a new technique based on microcalorimetry. The blends were characterised by scanning electron microscopy (SEM), density measurements and thermogravimetry. Oxygen permeability was measured on the pure components and on some of the blends. The incorporation of PCL yielded a pronounced decrease in water vapour transmission rate of both chitosan and the WPI measured at a relative humidity gradient of 11 to 0%. A volume content of 17-18% of PCL lowered the water vapour transmission rate by 70-90%. It was found that the majority of the PCL particles were ellipsoidal in chitosan and fibrous in the WPI and the data indicated that the particle shape had an important influence on the water vapour transmission rate. The large decrease in water vapour transmission rate was also due to a reduction in water solubility because of limited swelling of the constrained chitosan or WPI matrix in the presence of PCL. SEM revealed that the miscibility/compatibility between PCL and the matrices was good. The water vapour transmission rate of the films decreased with increasing vacuum-drying time of the chitosan and WPI solutions. Microcalorimetry provided accurate estimates of water vapour transmission rate. Furthermore. this technique proved to be very flexible and the water vapour transmission rate could be determined over a broad range of relative humidities in a single experiment.

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