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  • 151.
    Ansari, Farhan
    et al.
    KTH.
    Rojas Escontrillas, Ramiro
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Molecular blending and reinforcing effect of lignin in ductile epoxy resins2017Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Artikel i tidskrift (Övrigt vetenskapligt)
  • 152.
    Ansari, Farhan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Zhou, Qi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Berglund, Lars
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH), Fiber- och polymerteknologi.
    Cellulose nanocomposites - Controlling dispersion and material properties through nanocellulose surface modification2015Ingår i: ICCM International Conferences on Composite Materials, International Committee on Composite Materials , 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    The use of cellulosic nanofibers as reinforcement in polymer composites offers great advantages over their petroleum counterparts. Apart from being strong, stiff and low density; they are obtained from naturally occurring resources and as such are favorable from an environmental point of view. A major problem while studying nanomaterials is their tendency to agglomerate, thus leading to inhomogeneous distribution within the polymer matrix. This often results in stress concentrations in the matrix rich regions when the material is subjected to load and therefore, limits the potential application of these materials. A common approach to circumvent this is by surface modification, which facilitates the dispersion in non-polar matrices. An environmental friendly approach, inspired by clay chemistry, was used to functionalize the CNC surface. It was shown that the CNC could be modified in a rather convenient way to attach a variety of functional groups on the surface. Primarily, the problem of cellulose nanocrystal (CNC) distribution in a hydrophobic polymer matrix is investigated. Composites prepared from modified CNC were studied and compared with unmodified CNC. The distribution of the CNC is carefully monitored at different stages via UV-Vis spectroscopy and scanning electron microscopy (SEM). The mechanical properties of the resulting materials were characterized by dynamic mechanical as well as uniaxial tensile tests. It was shown that a homogeneous distribution of the CNC exposes a tremendous amount of surface area to interact with the matrix. In such a case, the stress transfer is much more efficient and perhaps, the matrix behavior is modified, which leads to significant improvements in the mechanical properties.

  • 153.
    Ansari, Farhan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Salajkova, Michaela
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Zhou, Qi
    KTH, Skolan för bioteknologi (BIO), Glykovetenskap. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Lars, Berglund
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Strong surface treatment effects on reinforcement efficiency in biocomposites based on cellulose nanocrystals in poly(vinyl acetate) matrix2015Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, nr 12, s. 3916-3924Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the problem to disperse cellulose nanocrystals (CNC) in hydrophobic polymer matrices has been addressed through application of an environmentally friendly chemical modification approach inspired by clay chemistry. The objective is to compare the effects of unmodified CNC and modified CNC (modCNC) reinforcement, where degree of CNC dispersion is of interest. Hydrophobic functionalization made it possible to disperse wood-based modCNC in organic solvent and cast well-dispersed nanocomposite films of poly(vinyl acetate) (PVAc) with 1-20 wt % CNC. Composite films were studied by infrared spectroscopy (FT-IR), UV-vis spectroscopy, dynamic mechanical thermal analysis (DMTA), tensile testing, and field-emission scanning electron microscopy (FE-SEM). Strongly increased mechanical properties were observed for modCNC nanocomposites. The reinforcement efficiency was much lower in unmodified CNC composites, and specific mechanisms causing the differences are discussed.

  • 154.
    Ansari, Farhan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Sjöstedt, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Fiberteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Biocomposites based on nanostructured chemical wood pulp fibres in epoxy matrixManuskript (preprint) (Övrigt vetenskapligt)
  • 155.
    Ansari, Farhan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation.
    Sjöstedt, Anna
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Larsson, Per Tomas
    KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Berglund, Lars A.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellens Centrum BiMaC Innovation. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Hierarchical wood cellulose fiber/epoxy biocomposites: Materials design of fiber porosity and nanostructure2015Ingår i: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 74, s. 60-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Delignified chemical wood pulp fibers can be designed to have a controlled structure of cellulose fibril aggregates to serve as porous templates in biocomposites with unique properties. The potential of these fibers as reinforcement for an epoxy matrix (EP) was investigated in this work. Networks of porous wood fibers were impregnated with monomeric epoxy and cured. Microscopy images from ultramicrotomed cross sections and tensile fractured surfaces were used to study the distribution of matrix inside and around the fibers - at two different length scales. Mechanical characterization at different relative humidity showed much improved mechanical properties of biocomposites based on epoxy-impregnated fibers and they were rather insensitive to surrounding humidity. Furthermore, the mechanical properties of cellulose-fiber biocomposites were compared with those of cellulose-nanofibril (CNF) composites; strong similarities were found between the two materials. The reasons for this, some limitations and the role of specific surface area of the fiber are discussed.

  • 156.
    Ansari, Farhan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer.
    Skrifvars, M.
    Berglund, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Biokompositer. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Nanostructured biocomposites based on unsaturated polyester resin and a cellulose nanofiber network2015Ingår i: Composites Science And Technology, ISSN 0266-3538, E-ISSN 1879-1050, Vol. 117, s. 298-306Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biocomposites reinforced by natural plant fibers tend to be brittle, moisture sensitive and have limited strength. Wood cellulose nanofibers (CNF) were therefore used to reinforce an unsaturated polyester matrix (UP) without the need of coupling agents or CNF surface modification. The nanostructured CNF network reinforcement strongly improves modulus and strength of UP but also ductility and toughness. A template-based prepreg processing approach of industrial potential is adopted, which combines high CNF content (up to 45 vol%) with nanoscale CNF dispersion. The CNF/UP composites are subjected to moisture sorption, dynamic thermal analysis, tensile tests at different humidities, fracture toughness tests and fractography. The glass transition temperature (T-g) increases substantially with CNF content. Modulus and strength of UP increase about 3 times at 45 vol% CNF whereas ductility and apparent fracture toughness are doubled. Tensile properties at high humidity are compared with other bio-composites and interpreted based on differences in molecular interactions at the interface.

  • 157.
    Ansari, Mohd Farhan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Nanostructured Cellulose Biocomposites: Effects from dispersion, network and interface2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Trä och träbaserade material erbjuder ett hållbart alternativ till petroleumbaserade material. Mikrofibriller, eller som de också kallas i materialsammanhang, nanofibriller från cellulosa (CNF) är den huvudsakliga lastbärande komponenten i trä. Den har stor potential som förstärkande tillsats i polymerer. Denna studie handlar om kompositer baserade på nanocellulosa. Biokompositer med företrädesvis hög andel nanocellulosa framställs och karakteriseras. Huvudsyftet är att förklara inverkan av nanostruktur på makroskopiska egenskaper.

    I en första studie används polyvinylacetat (PVAc) som modellpolymer för att undersöka effekten av dispergeringgrad hos cellulosa-nanokristaller (CNC) för optiska och mekaniska egenskaper. En miljövänlig form av modifiering av CNC används för att förbättra dispergeringsgraden. Nanokompositer med upp till 20 vikts-% modifierad eller icke modifierad CNC studerades. Nanokompositer med väldispergerad CNC visade dramatiskt förbättrade egenskaper, eftersom nanopartiklarna kraftigt påskyndade fysikalisk åldring av PVAc så att den fick högre E-modul och hållfasthet.

    I avhandlingens andra del framställdes härdplastkompositer genom harts-impregnering av porösa CNF-nätverk, följt av härdning. Epoxi (EP) och omättade polyester (UP) användes som härdplaster. Volymsfraktionen CNF var mellan 15-50%. Reaktionshastigheten under härdning ökade kraftigt i närvaro av nanocellulosa med hög specifik yta. Troligen reagerade epoxigrupper med hydroxylgrupper på cellulosaytan, under förutsättning att katalytiska aminföreningar fanns tillgängliga. Hypotesen fick ytterligare stöd i en studie av monoepoxi + nanocellulosa. Den modifieringen visade sig också göra CNF-nätverket mindre hygroskopiskt, så att de hygromekaniska egenskaperna förbättrades. Mekaniska egenskaper hos EP- och UP-kompositer bestämdes med hjälp av dragprov vid olika luftfuktighet. EP-kompositerna visade bättre egenskaper vid hög fuktighet, främst pga de kovalenta bindningarna mellan EP och CNF. Effekter av CNF-Dispergering, CNF-nätverkets egenskaper och gränsytan CNF-härdplast analyserades. Slutligen jämfördes EP-kompositer baserade på CNF med kompositer från blekta massafibrer. CNF-kompositerna hade högre hållfasthet till följd av den låga diametern (inga problem med fiber-matris separation och sprickbildning vid låga töjningar) och kraftigt töjningshårdnande orsakad av CNF nätverket.

  • 158.
    Antoni, Per
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Functional Dendritic Materials using Click Chemistry: Synthesis, Characterizations and Applications2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Förfrågan efter nya och mer avancerade applikationer är en pågående process vilket leder till en konstant utveckling av nya material. För att förstå relationen mellan en applikations egenskaper och dess sammansättning krävs full förståelse och kontroll över materialets uppbyggnad. En sådan kontroll över uppbyggnaden hos material hittas i en undergrupp till dendritiska polymerer som kallas dendrimerer. I den här doktorsavhandlingen belyses nya metoder för att framställa dendrimer med hjälp av selektiva kemiska reaktioner. Sådana selektiva reaktioner kan hittas inom konceptet klickkemi och har i detta arbete kombinerats med traditionell anhydrid- och karbodiimidmedierad kemi.

    Denna avhandling diskuterar en accelererad tillväxtmetod, dendrimerer med inre och yttre reaktiva grupper, simultana reaktioner och applikationer baserade på dessa dendritiska material.

    En accelererad tillväxtmetod har utvecklats baserad på AB2- och CD2-monomerer. Dessa monomerer tillåter tillväxt av dendrimerer utan att använda sig av skyddsgruppkemi eller aktivering av ändgrupper. Detta gjordes genom att kombinera kemoselektiviteten hos klickkemi tillsammans med traditionell syraklorid kopplingar.

    Dendrimerer med inre alkyn- eller azidfunktionalitet syntetiserades genom att använda AB2C-monomerer. Den dendritiska tillväxten skedde med hjälp av karbodiimidmedierad kemi. Monomererna som användes bär på en C-funktionalitet, alkyn eller azid, och på så sätt byggs får interiören i de syntetiserade dendrimeren en inneburen aktiv funktionell grupp.

    Ortogonaliteten hos klickkemi användes för att sammanfoga monomerer till en dendritisk struktur. Traditionell anhydridkemi- och klickemireaktioner utfördes samtidigt och på så sätt kunde dendritiska strukturer erhållas med färre antal uppreningssteg.

    En ljusemitterande dendrimer syntetiserades genom att koppla azidfunktionella dendroner till en alkynfunktionell cyclenkärna. Europiumjoner inkorporerades i kärnan varpå dendrimerens fotofysiska egenskaper analyserades. Mätningarna visade att den bildade triazolen hade en sensibiliserande effekt på europiumjonen. Termiska studier på några av de syntetiserade dendrimerer utfördes för att se om några av dem kunde fungera som templat vid framställning av isoporösa filmer.

  • 159.
    Antoni, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Hed, Yvonne
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Nordberg, Axel
    KTH, Skolan för teknik och hälsa (STH), Neuronik (Stängd 20130701).
    Nyström, Daniel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    von Holst, Hans
    KTH, Skolan för teknik och hälsa (STH), Neuronik (Stängd 20130701).
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Bifunctional Dendrimers: From Robust Synthesis and Accelerated One-Pot Postfunctionalization Strategy to Potential Applications2009Ingår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 48, nr 12, s. 2126-2130Artikel i tidskrift (Refereegranskat)
  • 160.
    Antoni, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hed, Yvonne
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nordberg, Axel
    KTH, Skolan för teknik och hälsa (STH), Neuronik.
    Nyström, Daniel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    von Holst, Hans
    KTH, Skolan för teknik och hälsa (STH), Neuronik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    One-pot dendritic growth and post-functionalization of multifunctional dendrimers: Synthesis and application2009Manuskript (preprint) (Övrigt vetenskapligt)
  • 161.
    Antoni, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Vamvounis, George
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nyström, Daniel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nyström, Andreas
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindgren, Mikael
    Norwegian Univ Sci & Technol, Dept Phys.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Europium confined cyclen dendrimers with photophysically active triazoles2008Ingår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 18, nr 22, s. 2545-2554Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dendrimers up to the fourth generation (G1-G4) were successfully synthesized via the efficient copper catalyzed 1,3-dipolar cycloaddition between primary alkynes and azides (CuAAC), also referred to as a click reaction. The synthetic protocol involved the preparation of presynthesized dendron wedges that subsequently were attached to a tetra-valent alkyne functional cyclen core. These constructed structures integrated stable triazole groups "intra-locked'' between the cyclen and dendron wedges. The incorporation of a lanthanide metal ion, europium, into the interior of all cyclen dendrimers was monitored by FT-IR. Interestingly, the photophysical results showed that the proximate triazole not only acts as a stable linker but also as a sensitizers, transferring its singlet-singlet excitation in the ultraviolet region (270-290 nm) to the partially filled luminescent lanthanide 4f shell. An increase of luminescence decay time from the lanthanide D-5(0) -> F-7(2) emission was observed with increasing dendrimer size, indicating that the shielding effect of the dendron wedges is important for the relaxation of the photo-excitation and energy transfer. To the best of our knowledge, this is the first time a set of dendron wedges have successfully been attached to a cyclen metal ion cage via the versatile click reaction. Furthermore, the produced triazoles intra-locked in close proximity to the macrocycle core elucidated an interesting photophysical function.

  • 162.
    Antoni, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nyström, Daniel
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hawker, Craig
    Univ Calif Santa Barbara, Mat Res Lab.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    A chemoselective approach for the accelerated synthesis of well-defined dendritic architectures2007Ingår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, nr 22, s. 2249-2251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A chemoselective and layered growth approach has been developed for the synthesis of dendrimers, combining Click chemistry with traditional esterification/etherification reactions, without the need for activation steps and with excellent overall yields.

  • 163.
    Antoni, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nyström, Daniel
    KTH, Skolan för kemivetenskap (CHE).
    Ropponen, Jarmo
    KTH, Skolan för kemivetenskap (CHE).
    Lundberg, Pontus
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Click chemistry as a tool for accelerated and one-pot synthesis of dendrimers: thermal study and application2007Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Dendrons, dendrimers and linear polymers have been synthesized using click chemistry in combination with anhydride chemistry and atom transfer radical polymerization, ATRP. Functional materials were obtained in multigram scale using these orthogonal chemistries simultaneous.

  • 164.
    Antoni, Per
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Robb, Maxwell J.
    Campos, Luis
    Montanez, Maria
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hult, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malmström, Eva
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Malkoch, Michael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Hawker, Craig J.
    Pushing the Limits for Thiol-Ene and CuAAC Reactions: Synthesis of a 6th Generation Dendrimer in a Single Day2010Ingår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 43, nr 16, s. 6625-6631Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Dendrimer synthesis should not be tedious and time-consuming. By utilizing an AB(2)-CD2 approach and having orthogonal, "clickable" groups on each monomer, the time for dendrimer assembly can be drastically reduced. This was shown by preparation of a sixth generation dendrimer from starting monomer units in a single day.

  • 165.
    Antonsson, Stefan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Strategies for improving kraftliner pulp properties2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    En stor del av världens papperstillverkning utgörs av produktion av wellpappkomponenter, kraftliner och fluting, som används i en uppsjö av olika wellpapplådor. När dessa lådor lagras och transporteras utsätts de ofta för förändringar i relativa luftfuktigheten. Dessa förändringar tillsammans med mekanisk belastning ökar lådornas deformation jämfört med om samma belastning skulle ha applicerats vid ett statiskt klimat. Denna förhöjda krypning på grund av förändringarna i relativ luftfuktighet kallas mekanosorptiv- eller accelererad krypning. Mekanosorptiv krypning tvingar producenterna att ha höga säkerhetsmarginaler vid dimensioneringar av lådor och är därför en av nyckelegenskaperna för kraftliner.

     

    Olika strategier för att minska denna effekt, och på samma gång erövra mer kunskap om orsakerna till detta fenomen, har varit syftet med arbetet. Derivatiserade och oderivatiserade svartlutslignin, en biprodukt möjlig att få ut i stora kvantiteter från massabruk, har används tillsammans med biomimetriska metoder, för att modifiera kraftlinermassas egenskaper. Dessutom har kraftlinermassans egenskaper jämförts med andra massors egenskaper för att utvärdera inverkan av fibermorfologiska faktorer, såsom fiberbredd och fibreform på det mekanosorptiva krypet. Också inverkan av den kemiska sammansättningen av kraftliner massan har undersökts både genom behandling med klorit och xylanas och genom att producera massor med olika kemiska sammansättningar.

     

    Genom att använda lignin och biomimetriska metoder för att skapa radikal-kopplingsreaktioner har det visats på möjligheten att öka våtstyrkan i massa-ark. Det här sättet att behandla massa visade dessvärre inga signifikanta effekter på det mekanosorptiva krypet. Tillsatts av ett apolärt suberin-liknande ligninderivat, som visats möjligt att producera ur naturliga råmaterial, visade en positiv effekt på det mekanosorptiva krypegenskaperna även om det var på bekostnad av styvheten vid konstant klimat. Olika massor jämfördes med en kraftlinermassa och det observerades att relationen mellan dragstyvhet och hygroexpansion kan användas för att uppskatta de mekanosorptiva krypegenskaperna. Lövvedssulfatmassorna som undersöktes hade lägre hygroexpansion, antagligen beroende på smalare och rakare fibrer, och högre dragstyvhet, troligen beroende på en lägre ligninhalt. När ligninhalten varierades i sulfatmassor med olika metoder observerades att ökad ligninhalt ger en ökad hygroexpansion och minskad dragstyvhet liksom en ökad mekanosorptiv krypning. Dessutom fanns indikationer på en ökad mekanosorptiv krypning till följd av högre xylaninnehåll.

  • 166.
    Antonsson, Stefan
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    The Use of Lignin Derivatives to Improve Selected Paper Properties2007Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Ved består huvudsakligen av tre typer av polymerer, cellulosa, hemicellulosa och lignin. Lignin bildas i naturen genom enzymatiskt initierad oxidativ koppling av tre olika typer av fenylpropan-enheter. Dessa bygger genom olika kol-kol- och kol-syre-bindningar upp en amorf tredimensionell polymer. När kemisk massa tillverkas bryts lignin ner och löses ut i kokluten. Luten innehåller de förbrukade kokkemikalierna och bränns generellt i en sodapanna för att regenerera kemikalierna och producera ånga. Sodapannan är emellertid dyr. Därför har den blivit produktionsbegränsande på många massabruk. Att avlägsna en del av ligninet från avluten vore därför önskvärt och att finna ekonomiskt intressanta produkter baserade på lignin från svartlut är därför ett viktigt forskningsområde .

    Ett lämpligt område för ligninprodukter vore som tillsatts i oblekt massa. Oblekt massa används till stor del för tillverkning av kraftliner, topp- och bottenskikten på wellpapp. När lådor av wellpapp lagras i containrar som färdas över haven, förändras den relativa luftfuktigheten. Detta gör att lådorna kollapsar lättare än om de skulle ha lagrats vid konstant luftfuktighet, även en hög sådan. Detta är på grund av det så kallade mekanosorptiva- eller accelererade krypfenomenet. Genom tillsatts av våtstyrkemedel till kraftliner eller behandla den med hydrofoba ämnen, finns indikatoner på att mekanosorptiva effekten skulle kunna minska.

    För att försöka minska den effekten har ett lågmolekylärt kraftlignin, som utvunnits med hjälp av tvärsflödesfiltrering av svartlut och svavelsyrafällning, använts. Genom derivatisering av detta lignin med linolja erhölls ett hydrofobt ligninderivat som uppvisar strukturella likheter med biopolymeren suberin. När detta suberinlika ligninderivat tillsätts till massa verkar det mekanosorptiva krypet minska. När lågmolekylärt lignin används tillsammans med ligninradikalinitiatorerna lackas eller mangan(III) i kraftlinermassa erhålls dessutom en våtstyrka på ca 5% av torrstyrkan. Efter aminering av detta lignin gav en tillsatts till kraftlinermassan en våtstyrka på upp till 10% av torrstyrkan. Det finns indikationer på att det mekanosorptiva krypet samtidigt minskar när dessa behandlingar görs som ger upphov till ökad våtstyrka.

  • 167.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE).
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Biomimetic synthesis of suberin for new biomaterials2005Ingår i: Appita Annual Conference: Vol 2, 2005, s. 561-564Konferensbidrag (Refereegranskat)
    Abstract [en]

    Suberin is the biopolymer giving cork (oak bark) its hydrophobic and resistant characteristics. It acts as a diffusion barrier in bark and roots of plants. Similarly to lignin, it is a phenolic polymer with good affinity to cellulose and other wood polysaccharides, but it also contains polyaliphatic and strongly hydrophobic elements. In order to produce a lignin derivative similar to suberin, a desired lignin starting material should be of low molecular weight and have a high content of hydroxylic phenolic groups. By means of cross flow nanofiltration of softwood kraft pulping black liquor and pH-precipitation with diluted sulphuric acid, such a lignin has been obtained. Due to the fact that too much organics entering the recovery boiler frequently is the bottleneck for pulp production increases, a removal of part of the lignin can be economically very favourable. By using this lignin together with linola oil, a linseed oil with a large amount of unsaturated structures, an attempt was made to create a new hydrophobic lignin derivative similar tosuberin. The product was analysed with FT-IR, Fourier Transformed Infra Red Spectroscopy and GPC, Gel Permeation Chromatography. The suberin like material obtained from this lignin could be polymerised on thermo mechanical pulp fibres by means of Mn(III)-driven phenolic coupling. The ability of the suberin monomers to act as a hydrophobic paper coating was evaluated with contact angle measurements and the results indicate that this lignin derivative was potentially of interest due to its capability to interact well with wood fibres and make paper hydrophobic.

  • 168.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Johansson, Mats
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Low Mw-lignin fractions together with vegetable oils as available oligomers for novel paper-coating applications as hydrophobic barrier2008Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 27, nr 1, s. 98-103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lignin residues are available in large amounts as kraft lignin from chemical pulping processes. This lignin is mainly incinerated in recovery boilers. The recovery boilers are often the bottle-necks in the overall pulping process when pulp production increases are desired. Through cross-flow nano-filtration of the black liquor from kraft pulping, a low-molecular weight lignin fraction can be removed thus decreasing the organic load on the recovery boilers. The low-molecular weight lignin fraction furthermore exhibit different characteristics compared to other commercial kraft lignins and represents a new raw material source in novel applications.

    The low-molecular weight lignin was used together with a vegetable oil to produce a new hydrophobic lignin derivative similar to suberin. The lignin and the lignin derivative was analysed with FT-IR, UV-vis and SEC. The ability of the product to make paper surfaces hydrophobic was also evaluated.

    The results demonstrate the possibility to make a suberin-like lignin derivative that is potentially of interest in paper-coating applications due to its capability to interact well with wood fibres and make paper hydrophobic.

  • 169.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikael
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    The utilization of lignin derivatives and radical coupling reaction to increase wet strength of kraftliner2006Ingår i: 6th international paper and coating chemistry symposium. Book of abstracts., 2006, s. 55-55Konferensbidrag (Refereegranskat)
  • 170.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Adding lignin derivatives to decrease the effect of mechano-sorptive creep in linerboard2008Ingår i: Appita journal, ISSN 1038-6807, Vol. 61, nr 6, s. 468-471Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When load is applied to any type of paper while varying the relative humidity, the paper will creep more than if the same load is applied at constant humidity. This behaviour is called mechano-sorptive creep or accelerated creep, and the reasons for its occurrence in paper are still not fully understood. However, wet strength and the addition of apolar (hydrophobic) compounds to sheets have previously been suggested as factors improving the mechano-sorptive creep performance.

    This work evaluates a method for improving wet strength and tests the addition of a hydrophobic compound, with particular reference to mechano-sorptive creep stiffness. Wet strength was improved by subjecting kraft liner pulp to low-molecular-weight lignin, obtained by cross-flow filtration, and to the radical initiator manganese(III). The hydrophobic compound added was a suberin-like lignin derivative. Adding the suberin-like lignin derivative significantly increased the mechano-sorptive creep stiffness, even though the stiffness at 90% rh decreased in the tested samples. This was probably because of the decrease in hygroexpansion caused by this hydrophobic additive.

    Even though it is possible significantly to increase the wet strength of kraft liner pulp by adding manganese(III) and cross-flow-filtered lignin, doing so has no significant effect on mechano-sorptive creep stiffness.

  • 171.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The influence of lignin and xylan on some kraftliner pulp properties2009Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 4, s. 403-408Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study investigates the influence of lignin and hemicellulose content on the mechanical and physical properties of softwood kraft liner pulp. Tensile properties, hygroexpansion, and mechano-sorptive creep properties were measured. The lignin and hemicellulose contents were modified by chlorite delignification and xylanase treatment.

    After treatment, the chemical composition of the pulps was 3-14% Klason lignin, 69-77% cellulose, 16-21% hemicellulose, and 4-7% xylan. In the tested pulps, low lignin content tended to decrease hygroexpansion as well as increase tensile stiffness and mechano-sorptive creep stiffness. Xylan contributed less to the pulp sheet properties, but at equal lignin contents, higher xylan content tended to give increased hygroexpansion and worse mechano-sorptive creep properties.

  • 172.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Karlström, Katarina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Applying a novel cooking technique to produce high kappa number pulps: the effects on physical properties2009Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 4, s. 415-420Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A recently developed kraft cooking technique, with a longer impregnation time at lower temperatures to facilitate diffusion over consumption of active cooking chemicals, makes it possible to produce kraftliner pulp without inline refining. This technique was applied to prepare two pulps with different lignin contents, which were compared with two industrial pulps from conventional kraft cooks in order to evaluate the physical properties of the pulps.

    It was demonstrated that pulps with lower lignin content can increase tensile stiffness, decrease hygroexpansion, and decrease the mechano-sorptive creep of handsheets. However, no difference in SCT and tensile energy absorption values due to different lignin contents was observed. It was further demonstrated that pulps made with Extended Impregnation Cooking (EIC) results in straighter pulp fibres with higher cellulose content. These pulps tended to have lower mechano-sorptive creep than conventional pulps. A higher brightness of the pulp sheets can also be obtained by choosing a higher alkali profile.

  • 173.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Mäkelä, Petri
    Innventia AB.
    Fellers, Christer
    Innventia AB.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi. KTH, Skolan för kemivetenskap (CHE), Centra, Wallenberg Wood Science Center.
    Comparison of the physical properties between hardwood and softwood pulps2009Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 24, nr 4, s. 409-414Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    High mechano-sorptive creep resistance, i.e., good creep resistance in environments with changing relative humidity, is one of the key requirements for linerboards. The aim of this study was to investigate the influence of pulp types and pulp properties on the mechano-sorptive creep of kraftliner. A high-yield softwood, kraftliner pulp, and four different hardwood pulps were investigated. The physical properties of laboratory sheets were evaluated, with emphasis on the mechano-sorptive creep properties.

    The results showed that the density increase due to increased beating significantly improved the tensile stiffness of all pulps, while its effect on the isocyclic creep stiffness was less pronounced. The hardwood pulps showed higher tensile stiffness, better mechano-sorptive creep properties, and lower hygroexpansion than the softwood pulp at a given density. However, the softwood pulp did exhibit better tensile strength and fracture toughness properties than the hardwood pulps.

    The results imply that hardwood pulps can be competitive with softwood pulps in kraftliners, provided that their tensile strength and fracture toughness properties can be improved by, for example, chemical means. Furthermore, the isocyclic creep stiffness correlates with the ratio of tensile stiffness to hygroexpansion, indicating that this ratio can be used for engineering estimates of the mechano-sorptive creep performance of paper materials.

  • 174.
    Antonsson, Stefan
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Pulkkinen, Iiro
    Chemical Engineering, Department of Biotechnology and Chemical Technology, Helsinki University of Technology (TKK), Espoo, Finland.
    Fiskari, Juha
    Metsä-Botnia, Joutseno Mill, Lappeenranta, Finland.
    Karlström, Katarina
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Lindström, Mikael E.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    The relationship between hygroexpansion, tensile stiffness, and mechano–sorptive creep in bleached hardwood kraft pulps2010Ingår i: Appita journal, ISSN 1038-6807, Vol. 63, nr 1, s. 231-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hygroexpansion coefficient and tensile stiffness are important parameters in many paper applications. This study compares several bleached industrial hardwood kraft pulps, comprising five eucalypt pulps from South America, Europe, and Africa as well as an acacia pulp from Asia and a birch pulp from Scandinavia. Refined and unrefined pulps are compared. The results indicate significant differences in hygroexpansion but smaller differences in tensile stiffness index at comparable densities. No single factor offering a reasonable explanation of these differences in hygroexpansion coefficient, such as carbohydrate composition, fibre dimensions, or fibre form, was found. However, correlation between hygroexpansion coefficient and the mechano-sorptive creep stiffness was observed. We suggest that the hygroexpansion coefficient at a given tensile stiffness level can be used to rank pulps in terms of their mechano-sorptive creep properties.

  • 175. Arabasadi, Z.
    et al.
    Khorasani, M.
    Akhlaghi, Shahin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Fazilat, H.
    Gedde, Ulf W.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Hedenqvist, Mikael S.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymera material.
    Shiri, M. E.
    Prediction and optimization of fireproofing properties of intumescent flame retardant coatings using artificial intelligence techniques2013Ingår i: Fire safety journal, ISSN 0379-7112, E-ISSN 1873-7226, Vol. 61, s. 193-199Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A multi-structured architecture of artificial intelligence techniques including artificial neural network (ANN), adaptive neuro-fuzzy-inference-system (ANFIS) and genetic algorithm (GA) were developed to predict and optimize the fireproofing properties of a model intumescent flame retardant coating including ammonium polyphosphate, pentaerythritol, melamine, thermoplastic acrylic resin and liquid hydrocarbon resin. By implementing ANN on heat insulation results of coating samples, prepared based on a L16 orthogonal array, mean fireproofing time (MFPT) values were properly predicted. The predicted data were then proved to be valid through performing closeness examinations on fuzzy inference systems results regarding their experimental counterparts. However, the possible deviations tapped into phenomena like foam detachment and char cracking were alleviated by ANFIS modeling embedded with pertinent fuzzy rules based on the sole and associative practical role of used additives. The contribution of each intumescent coating component on the formulation with optimized fireproofing behavior was then explored using GA modeling. A similar optimization procedure was also conducted using conventional Taguchi experimental design but the GA based optimized intumescent coating was found to exhibit higher MFPT value than that suggested by the Taguchi method.

  • 176. Arasteh, Rouhollah
    et al.
    Naderi, Ali
    Kaptan, Navid
    Maleknia, Laleh
    Akhlaghi, Shahin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nazockdast, Hosein
    Effects of Fiber Spinning on the Morphology, Rheology, Thermal, and Mechanical Properties of Poly(trimethylene terephthalate)/Poly(ethylene terephthalate) Blends2014Ingår i: Advances in Polymer Technology, ISSN 0730-6679, E-ISSN 1098-2329, Vol. 33, nr S1, s. 21443-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The morphology, thermal behavior, rheological, and mechanical properties of poly(trimethylene terephthalate) (PTT)/poly(ethylene terephthalate) (PET) blend fibers were investigated. The scanning electron microscopy studies revealed the formation of a microfibrillar network of the PET within the PTT matrix after the fiber-spinning process. Differential scanning calorimetry results demonstrated that although the thermal characteristics of the amorphous phase were unaffected by the fiber-spinning process, the melting and crystallization behavior of the blends was altered by the elongation flow imposed during the melt spinning. The viscoelastic behavior of the PTT/PET blends was also studied by a steady shear rate and dynamic sweep rheological experiments before and after the spinning process. The induced morphology and crystallization reordering resulting from the fibrillation process are shown to have a remarkable effect on the complex viscosity profile of the PTT/PET fibers, particularly in the blend containing 30 wt% PET. The mechanical testing showed that tenacity and Young's modulus of the PTT fibers increased with the addition of PET up to 30 wt%.

  • 177.
    Areskogh, Dimitri
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Structural Modifications of Lignosulphonates2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Lignosulphonates are by‐products from the sulphite pulping process for the manufacture ofspecialty dissolving pulps and paper. During the liberation of the cellulose, the lignin isfractionated and solubilised through covalent addition of sulphonic acid groups at variouspositions in the structure. The formed sulphonated lignin, lignosulphonate is then furtherisolated and refined.

    The amphiphilic nature of lignosulphonates has enabled them to be used as additives to varioussuspensions to improve their dispersion and stability. The by far largest utilisation oflignosulphonates is as dispersants in concrete. Here, lignosulphonates act by dispersing cementparticles to prevent flocculation, un‐even particle distribution and reduced strengthdevelopment. The dispersion is achieved through steric and electrostatic repulsion of the cementparticles by the lignosulphonate polymer. This behaviour is intimately linked with the overallsize and amount of charged groups in the dispersing polymer. Traditional modifications oflignosulphonates have been limited to removal of sugars, filtration and fractionation. Thesemodifications are not sufficient for utilisation of lignosulphonates in high‐strength concrete. Heresynthetic dispersants and superplasticisers are used which are considerably more efficient evenat low dosages. To compete with these, additional modifications of lignosulphonates are likely tobe necessary. The molecular weight and functional group composition have been identified anddescribed as the most interesting parameters that can be modified.

    Currently, no suitable method exists to increase the molecular weight of lignosulphonates.Oxidation by the natural radical initiating enzyme laccase is an interesting tool to achieve suchmodifications. In this thesis several aspects of the mechanism through which this enzyme reactswith lignin and lignosulphonate structures have been elucidated through model compoundstudies. Further studies showed that laccase alone was a highly efficient tool for increasing themolecular weight of commercial lignosulphonates at low dosages and in short incubation times.Immobilisation of the laccase to a solid support to enable re‐utilisation was also investigated.

    Modification of functional group composition of lignosulphonates was achieved throughozonolysis and the Fenton’s reagent, a mixture of hydrogen peroxide and iron(II)acetate.Introduction of charged carboxylic groups was achieved through opening of the benzyl rings oflignosulphonates. It was found that a two‐stage process consisting of laccase oxidation followedby ozonolysis was an efficient technique to create a polymer enriched with carboxylic acidgroups with a sufficient molecular size.

    Oxidation by the Fenton’s reagent was shown to yield similar modifications as the combinedlaccase/ozonolysis treatment albeit with less pronounced results but with a large level of controlthrough variation of a number of reaction parameters. The Fenton’s reagent can therefore be aninteresting alternative to the aforementioned two‐stage treatment.

    These modifications are interesting for large‐scale applications not only because of theirsimplicity in terms of reaction parameters but also because of the ubiquity of the used enzymeand the chemicals in the pulp and paper industry.

  • 178.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Fenton's reaction: a simple and versatile method to structurally modify commercial lignosulphonates2011Ingår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 26, nr 1, s. 90-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Treatment of lignosulphonates with hydrogen peroxide and Fe (II) acetate under mild conditions can be used to increase the molecular weight and content of carboxylic acids. Such Fenton's oxidation can produce, in some of the conditions of and lignosulphonate concentration, a two-fold increase in the molecular weight and a 6-7 fold increase in the carboxylic acid content. The structural modifications of lignosulphonate may increase the technical performance of the product in several applications. Possible reaction mechanisms of the Fenton system are proposed and discussed.

  • 179.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Immobilisation of laccase for polymerisation of commercial lignosulphonates2011Ingår i: Process Biochemistry, ISSN 1359-5113, E-ISSN 1873-3298, Vol. 46, nr 5, s. 1071-1075Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The oxidoreductive enzyme laccase has previously been shown to be able to increase the average molecular weight of lignosulphonatesthrough generation of phenoxy radicals on end groups and the subsequent radical-radical coupling reactions that cross-link individual lignosulphonate molecules. Utilisation of laccases for this purpose is a potential industrial process not only to improve the properties of technical lignosulphonates but also to expand their utilisation to new areas. Immobilisation of the laccase is an interesting technique to enable reusage of the enzyme and thus reduce costs involved with such process. In this work, we demonstrate the potential of immobilised laccase to polymerise technical lignosulphonates. A number of factors that limits re-utilisation of the immobilised catalyst such as lignosulphonate adsorption onto the carrier and laccase deactivation have been identified and are discussed. However, by using a low-porosity support and lower reaction temperatures these problems can be limited.

  • 180.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Investigation of the Molecular Weight Increase of Commercial Lignosulfonates by Laccase Catalysis2010Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, nr 4, s. 904-910Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lignosulfonates are by-products from the sulfite pulping process. During this process, lignin is liberated from pulp fibers through sulfonation and washed away. As a consequence, the lignosulfonate molecules contain both hydrophobic and hydrophilic moieties. Lignosulfonates are low-value products with limited performance and are used as such as binders, surfactants, and plasticizers in concrete. Lignosulfonates face strong competition from synthetic petroleum-based plasticizers with superior quality. Therefore, increasing the performance of lignosulfonates is desirable not only from a sustainability point of view but also to expand their usage. One important aspect that describes how well lignosulfonates can act as plasticizers is the molecular weight. In this paper, the molecular weight of four commercial lignosulfonates is increased through oxidation by two laccases without utilization of mediators. Different parameters to obtain maximal molecular weight increase were identified and the technical significance of the experiments is discussed.

  • 181.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Polymerization of lignosulohonates by laccase - from model studies to application evaluation trials2010Ingår i: Oxidative enzymes as sustainable industrial biocatalysts / [ed] G Feijoo and MT Moreira, 2010, s. 151-156Konferensbidrag (Refereegranskat)
  • 182.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Reaction mechanism of laccase-catalyzed polymerization of lignin revealed with model study2008Ingår i: 10th European workshop on lignocellulosics and pulp proceedings, 2008, s. 101-104Konferensbidrag (Refereegranskat)
  • 183.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Structural modification of commercial lignosulphonates through laccase catalysis and ozonolysis2010Ingår i: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 32, nr 3, s. 458-466Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lignosulphonates are by-products from the sulphite pulping process, in which lignin is separated from cellulose by the addition of sulphonic acid groups to the alpha-position of lignin, thereby increasing the solubility of lignin in water. The predominant industrial utilisations of lignosulphonates are as dispersants, plasticisers and water-reducing agents in concrete preparation. The ability of lignosulphonates to function as a good plasticisers and water reducers is intimately linked with the purity of the lignosulphonate, its molecular weight and the number of charged groups present in the macromolecule. Currently, lignosulphonates are outrivaled by synthetic plasticisers termed superplasticisers due to their superior properties when used as additives to high-strength concrete. If lignosulphonates are to successfully compete with these superplasticisers, significant modifications are required. This paper describes a two-stage treatment of lignosulphonates in which the molecular weight is increased through laccase oxidation and carboxylic groups are introduced through ozonolysis. The technical significance of the results is also discussed.

  • 184.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Nousiainen, Paula
    University of Helsinki, Department of Chemistry.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Sipilä, Jussi
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Träkemi och massateknologi.
    Oxidative polymerisation of models for phenolic lignin end-groups by laccase2010Ingår i: Holzforschung, ISSN 0018-3830, E-ISSN 1437-434X, Vol. 64, nr 1, s. 21-34Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The redox enzyme laccase can lead to cross-linking of lignin molecules by oxidising phenolic end groups to resonance-stabilised radicals that can undergo radical coupling to form covalent bonds. This property has potential for many technical applications. However, laccase treatment can also lead to degradation. Experiments were performed with two laccases of different oxidation potential and pH and temperature optima. The predominant reaction following laccase oxidation is the formation of 5-5' and 4-O-5' bonds. If the 5-position is blocked, other reactions occur, including coupling of the 1-position and oxidation of the a-position, which aggravates cross-linking of different lignin molecules. The product profile generated by the two laccases is somewhat different, mainly because of the different pH rather than differences in enzyme activity. Reaction mechanisms and the technical and biological significance of the results are discussed.

  • 185.
    Areskogh, Dimitri
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Nousiainen, Paula
    University of Helsinki, Department of Chemistry.
    Li, Jiebing
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Gellerstedt, Göran
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Sipilä, Jussi
    Henriksson, Gunnar
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Träkemi och massateknologi.
    Sulfonation of phenolic end groups in lignin directs laccase-initiated reactions towards cross-linking2010Ingår i: Industrial Biotechnology, ISSN 1550-9087, E-ISSN 1931-8421, Vol. 6, nr 1, s. 50-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of sulfonation of the a-carbon on model compounds representing phenolic end groups on lignin was studied with respect to the reactions initiated by oxidation of laccase, by mass spectrometry. Sulfonation seems to direct the reactions towards formation of 5-5´ and 4-O-5´ bonds, avoiding formation of 1-O-4´ bonds and oxidation of the a-carbon. This, in turn, will facilitate cross-linking reactions between lignin molecules. Sulfonation therefore has potential as an industrial pretreatment prior to laccase treatment for various wood-containing materials.

  • 186.
    Arias Goa, Veluska
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Macrostructural Design of Polylactide-based Materials for Improved Mechanical and Degradation Properties2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 187.
    Arias, Veluska
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Towards a retro-structural design of degradable aliphatic polyester-based materials2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The increasing amount of accumulated plastic waste has led to a continuous search for degradable materials for use in a variety of applications. This eco-friendly approach contemplates the use of degradable alternatives to the inert polymers (the main components in plastics) used today and further engineering of their degradation pathways. The most extensively investigated group of degradable polymers is the poly(α-esters), due to their tailorable thermo-mechanical properties and degradability. However, degradation of these polymers can be undesirable or desirable depending on the time of occurrence. Thus, by controlling the degradation process, it is possible to predict and, consequently, tailor the materials’ lifetime for specific needs.Herein, a methodology to allow for a retro-structural design of degradable materials based on aliphatic polyesters is presented. Insights into the degradation behavior of the systems were obtained and further translated to different levels of structural designs to achieve desired macroscopic properties in terms of performance and degradability. Several combinational strategies based on polymer morphology, polymer structure and block design, were developed. As a result, homopolymers and block copolymers with projected degradation for different instances were created. Apart from bulk modifications in the material, it was shown that it was possible to tailor degradation pathways by means of specific interactions between polymer pairs in block copolymers and also in polymer blends. Furthermore, well-defined structure-property relationships are crucial when designing materials with specific degradability properties. In light of this, degradable polyester-based particles with tunable crystalline structures and, hence, physical properties, were developed. These particles proved to function as reinforcing agents in the creation of “green” homocomposites. These composites are promising alternatives in the search for materials that are completely degradable and sustainable.

  • 188.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Höglund, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Polylactides with "green" plasticizers: Influence of isomer composition2013Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 130, nr 4, s. 2962-2970Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Synthesized polylactides (PLA) with different D-isomer contents in the polymer chain were melt-blended with a series of green plasticizers by extrusion. Mechanical and thermal properties as well as the morphology of the plasticized materials were characterized to demonstrate how the combination of PLA with different D-contents and plasticizer controls the material properties. After addition of acetyl tributyl citrate (ATC), the elongation at break for PLA with a low D-isomer content was twice as high as that for PLAs with high D-isomer contents. Similar variations in the plasticization effect on the PLAs were also observed with the other plasticizers used, glyceryl triacetate (GTA), glycerol trihexanoate (GTH) and polyethylene glycol (PEG). In order to continue with the development of renewable polymers in packaging applications, the interrelation between a plasticizer and a specific polymer needs to be understood.

  • 189.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Höglund, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Tailoring the hydrolytic endurance of Poly(L-lactide)-based products2014Ingår i: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 248Artikel i tidskrift (Övrigt vetenskapligt)
  • 190.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Höglund, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Tuning the Degradation Profiles of Poly(L-lactide)-Based Materials through Miscibility2014Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 15, nr 1, s. 391-402Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effective use of biodegradable polymers relies on the ability to control the onset of and time needed for degradation. Preferably, the material properties should be retained throughout the intended time frame, and the material should degrade in a rapid and controlled manner afterward. The degradation profiles of polyester materials were controlled through their miscibility. Systems composed of PLLA blended with poly[(R,S)-3-hydroxybutyrate] (a-PHB) and polypropylene adipate (PPA) with various molar masses were prepared through extrusion. Three different systems were used: miscible (PLLA/a-PHB5 and PLLA/a-PHB20), partially miscible (PLLA/PPA5/comp and PLLA/PPA20/comp), and immiscible (PLLA/PPA5 and PLLA/PPA20) blends. These blends and their respective homopolymers were hydrolytically degraded in water at 37 degrees C for up to I year. The blends exhibited entirely different degradation profiles but showed no diversity between the total degradation times of the materials. PLLA presented a two-stage degradation profile with a rapid decrease in molar mass during the early stages of degradation, similar to the profile of PLLA/a-PHB5. PLLA/a-PHB20 presented a single, constant linear degradation profile. PLLA/PPA5 and PLLA/PPA20 showed completely opposing degradation profiles relative to PLLA, exhibiting a slow initial phase and a rapid decrease after a prolonged degradation time. PLLA/PPA5/comp and PLLA/PPA20/comp had degradation profiles between those of the miscible and the immiscible blends. The molar masses of the materials were approximately the same after 1 year of degradation despite their different profiles. The blend composition and topographical images captured at the last degradation time point demonstrate that the blending component was not leached out during the period of study. The hydrolytic stability of degradable polyester materials can be tailored to obtain different and predetermined degradation profiles for future applications.

  • 191.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik.
    Nano-Stereocomplexation of Polylactide (PLA) Spheres by Spray Droplet Atomization2014Ingår i: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 35, nr 22, s. 1949-1953Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A direct, efficient, and scalable method to prepare stereocomplexed polylactide (PLA)-based nanoparticles (NPs) is achieved. By an appropriate combination of fabrication parameters, NPs with controlled shape and crystalline morphology are obtained and even pure PLA stereocomplexes (PLASC) are successfully prepared using the spray-drying technology. The formed particles of varying D- and L-LA content have an average size of approximate to 400 nm, where the smallest size is obtained for PLA50, which has an equimolar composition of PLLA and PDLA in solution. Raman spectra of the particles show the typical shifts for PLASC in PLA50, and thermal analysis indicates the presence of pure stereocomplexation, with only one melting peak at 226 degrees C. Topographic images of the particles exhibit a single phase with different surface roughness in correlation with the thermal analysis. A high yield of spherically shaped particles is obtained. The results clearly provide a proficient method for achieving PLASC NPs that are expected to function as renewable materials in PLA-based nanocomposites and potentially as more stable drug delivery carriers.

  • 192.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Höglund, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites2015Ingår i: ACS Sustainable Chemistry & Engineering, ISSN 2168-0485, Vol. 3, nr 9, s. 2220-2231Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The demand for “green” degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of “green” homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300–500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young’s modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable.

  • 193.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Polymerteknologi.
    Odent, Jeremy
    Raquez, Jean-Marie
    Dubois, Philippe
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Toward "Green" Hybrid Materials: Core-Shell Particles with Enhanced Impact Energy Absorbing Ability2016Ingår i: ACS Sustainable Chemistry and Engineering, ISSN 2168-0485, Vol. 4, nr 7, s. 3757-3765Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Restrained properties of "green" degradable products drive the creation of materials with innovative structures and retained eco-attributes. Herein, we introduce the creation of impact modifiers in the form of core-shell (CS) particles toward the creation of "green" composite materials. Particles with CS structure constituted of PLA stereocomplex (PLASC) and a rubbery phase of poly(epsilon-caprolactone-co-D,L-lactide) (P[CL-co-LA]) were successfully achieved by spray droplet atomization. A synergistic association of the soft P[CL-co-LA] and hard PLASC domains in the core-shell structure induced unique thermo-mechanical effects on the PLA-based composites. The core-shell particles enhanced the crystallization of PLA matrices by acting as nucleating agents. The core-shell particles functioned efficiently as impact modifiers with minimal effect on the composites stiffness and strength. These findings provide a new platform for scalable design of polymeric-based structures to be used in the creation of advanced degradable materials.

  • 194.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Olsén, Peter
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Höglund, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Forecasting linear aliphatic copolyester degradation through modular block design2016Ingår i: Polymer degradation and stability, ISSN 0141-3910, E-ISSN 1873-2321, Vol. 130, s. 58-67Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The development of efficient methods to predict the degradation of renewable polymeric materials is continuously sought in the field of polymer science. Herein, we present a modular build-up approach to create polyester-based materials with forecasted degradation rates based on the hydrolysis of the constituent polymer blocks. This involved the strategic combination of critical factors affecting polyester hydrolysis, i.e. hydrophobicity and degree of crystallinity. The starting point of this method was a toolbox of polymers with different hydrophobicities and degrees of crystallinity, as well as an understanding of their inherent differences in hydrolysis rate. Knowledge of the hydrolysis of each polymer block module enabled the prediction of the overall degradation behavior of the constructed copolymers. Taking advantage of the primary factors that affect polymer degradation, block copolymers could be independently designed to incorporate soft or rigid and faster or slower degradation properties. This approach generated a shift for how molecular design can be used to predict the degradation behavior of intended materials for different applications.

  • 195.
    Arias, Veluska
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Olsén, Peter
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Odelius, Karin
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Höglund, Anders
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Selective degradation in aliphatic block copolyesters by controlling the heterogeneity of the amorphous phase2015Ingår i: Polymer Chemistry, ISSN 1759-9954, E-ISSN 1759-9962, Vol. 6, nr 17, s. 3271-3282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Controlling the course of the degradation of aliphatic polyesters is a key question when designing new degradable materials. It is shown herein that it is possible to predetermine the degradation path of aliphatic block copolyesters by controlling the heterogeneity of the amorphous phase, which in turn regulates the availability of the hydrolyzable groups in the polyester backbone. To demonstrate these processes, we synthesized a set of degradable materials based on poly(l-lactide) (PLLA), poly(ε-decalactone) (PεDL) and poly(ε-caprolactone) (PCL) with varying compositions. The materials were subjected to hydrolysis for a six months period. The materials composed of PLLA and PεDL exhibited a heterogeneous amorphous phase, whereas the materials composed of PCL and PεDL presented a more homogeneous phase. The kinetics of the degradation indicated that the slowest degradation rate was observed for the more homogeneous compositions. The degradation path of the heterogeneous amorphous phase materials was driven by a random chain scission process, whereas the more homogeneous composition presented a degradation path driven by a more selective chain scission. The confinement of the amorphous phase by the more hydrolytically stable PεDL permitted a selective degradation of the available hydrolyzable groups. The random and more selective chain scission processes were further verified by using previously determined molecular modeling based on Monte Carlo procedures. Topographical images and thermal analyses of the materials under different degradation periods correlated with the proposed degradation paths. Detailed insights and the ability to predetermine the degradation pathways of aliphatic polyesters will continue to expand the great potential of renewable materials and their use in specific applications for a future sustainable society.

  • 196.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Beccera, Marley
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Methling, Ralf
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Gortschakow, Sergey
    Inception of first mode negative streamers at mineral oil-solid interfacesManuskript (preprint) (Övrigt vetenskapligt)
  • 197.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Becerra, Marley
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. ABB Corp Res, Stockholm, Sweden.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pitois, Claire
    On the initiation of negative streamers at mineral oil-solid interfaces2015Ingår i: IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP), IEEE conference proceedings, 2015, s. 563-565Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper reports the probability distribution of negative streamers initiated in mineral oil with and without a solid interface. In addition, the charge injected by conduction currents prior to the streamer inception is presented. Impregnated paper and polymeric films made of PET, PTFE and PVDF are tested as solid materials. Comparison of the conduction charge for the different oil-solid interfaces is presented. It is found that the permittivity of the material used at the solid interface does not influence significantly the condition for streamer initiation in mineral oil. A nonlinear increasing of the charge readings for the impregnated paper, PET and PVDF cases are observed.

  • 198.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Becerra, Marley
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. ABB Corporate Research, Sweden.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Pitois, Claire
    ABB Corporate research .
    Propagation of negative streamers along mineral oil-solid interfaces2015Ingår i: Proceedings of the 2015 CEIDP Conference on Electrical insulation and Dielectric phenomena, CEIDP 2015, IEEE conference proceedings, 2015, s. 566-569Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper introduces an experimental study on the propagation of negative streamers along mineral oil-solid interfaces. A standard type of impregnated paper and different polymeric films (made of PET, PTFE and PVDF) are selected as solid materials immersed in mineral oil. The effect of the solid material on the streamer propagation along the interface formed with transformer oil is studied. Streamer velocities classified as first mode propagation point cathode are reported. Voltage gradient of the streamer channel and its stopping voltage are calculated for all the cases. Comparison of streamer charge and stopping length propagation are reported.  

  • 199.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Becerra, Marley
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Inception of first mode negative streamers at liquid/solid interfacesIngår i: Journal of Physics D: Applied PhysicsArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents an experimental study on the inception of first mode negative streamers at different mineral-oil/solid interfaces. This study is performed with a point-plane configuration immersed in mineral oil (point cathode). The mineral-oil/solid interface is done by assembling a solid in an inclined position into the point-plane gap. The solid is in contact (or in the proximity) with the point electrode tip. The tested solids are a kraft paper, a paper made from cellulosic micro and nano fibrils and different polymeric films (low density polyethylene (LDPE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF)). These solids have different relative permittivity and structural composition. It is found that the streamer inception voltage is statistically similar for the cases with solids with higher permittivity than mineral oil. The streamer inception voltage for the case without any solid barrier is also statistically similar to the cases with solids with higher permittivity than mineral oil. It is also found that the inception voltage is higher for streamers initiated at permittivity-matched interfaces (cases with LDPE and PTFE). Additionally, the influence of the spatial limitation with the solid surface to the volume where the streamer initiation process takes is performed with PTFE by varying the distance between the point electrode and the solid surface. It is shown that the streamer inception voltage depends on the distance between the point electrode and the solid surface. Furthermore, It is observed that the streamer inception voltage is also influenced when the distance between the point electrode and the surface of the PTFE is several micrometers (twenty times longer than the penetration depth of the avalanche responsible of streamer initiation). Additionally, it is also shown that a recently-proposed streamer inception criterion is unsuitable to predict the streamer inception conditions close to permittivity matched and mismatched liquid/solid interfaces.

  • 200.
    Ariza, David
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Becerra, Marley
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Hollertz, Rebecca
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi, Fiberteknologi.
    Wågberg, Lars
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknologi.
    Second Mode Positive Streamers Propagating Along Mineral-oil/solid InterfacesManuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    This paper presents an experimental study on second mode positive streamers propagating along mineral-oil/solid interfaces. The inception and propagation of these streamers is investigated with different impregnated solids (low density polyethylene (LDPE), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE) polyvinylidene fluoride (PVDF), two papers referred to as kraft paper and a kraft fibril paper, made from cellulosic micro and nano fibrils, a lignin-free paper and a paper with high lignin content referred to as k107 kraft paper). Streamers are initiated in a point-plane configuration under step voltages with 35 ns rise time. The radius of the tip is 2.9 μm and the solid is installed in an inclined position in close contact to the point electrode. Shadowgraphs, charge and light recording of the streamers are reported for each case. Furthermore, estimations of the streamer stopping length, velocity, current and average charge are reported. It is found that the streamer inception is influenced by the solid interface indicating that the inception process is not only conditioned by the field at the tip but also by the interface. A time delay is observed before the initiation of the streamer and probably correlated with the initiation process and formation of the gaseous phase. Additionally, the threshold propagation voltage of the second mode streamers at mineral-oil/solid interfaces is shown to be independent of the interface. It is also shown that the different characteristics of streamers propagating along the tested interfaces cannot be fully explained by the capacitive coupling effect due to permittivity mismatch. Thus, it is suggested that the characteristics of streamers propagating near interfaces is affected by other properties of the solid such as chemical composition, wettability and surface roughness.

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