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  • 1. Backman, A.C.
    et al.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Interaction between wood and polyvinyl acetate glue studied with dynamic mechanical analysis and scanning electron microscopy2004In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 91, no 5, p. 3009-3015Article in journal (Refereed)
    Abstract [en]

    The long-term properties of bonds are those that are of special interest. To achieve good bonds, the wood polymers and the adhering polymers must be compatible. This paper describes studies of the interaction of wood (Pinus sylvestris) with commercial polyvinyl acetate (PVAc) glue, polymethylmethacrylate (PMMA), and a more hydrophilic acrylate. Interaction was studied with a dynamic mechanical thermal analyzer (DMTA) operating in tensile mode in the tangential direction of wood. DMTA results were correlated with scanning electron microscopy (SEM) fractography studies of adhesion between polymers and wood on a cell wall level. The hypothesis put forward is that a good adhesion on the cell wall level results in a decrease in the glass transition temperature (Tg) measured with DMTA. A decrease in Tg for the hydrophilic acrylate was shown when it was impregnated in wood. The decrease of Tg was correlated with good adhesion to wood on the cell wall level. For PVAc and PMMA no decrease in Tg was measured when glued or impregnated in wood. SEM study also showed that the adhesion on a cell wall level was poor. The results show that DMTA can be a useful technique to study adhesion between wood and glue on a molecular level.

  • 2.
    Backman, A.C.
    et al.
    Luleå tekniska universitet.
    Lindberg, K.A.H.
    Luleå tekniska universitet.
    Interaction between wood and polyurethane-alkyd lacquer resulting in a decrease in the glass transition temperature2002In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 85, no 2, p. 595-605Article in journal (Refereed)
    Abstract [en]

    The long-term properties of paint and glue are of great interest to both manufacturers and users of these materials. If a good bond is achieved, the surface between the wood and the paint or glue will be less susceptible to degradation. Thus, the wood and polymer must be compatible and develop some kind of bonding force between them. A high degree of interaction between wood and commercial polyurethane-alkyd lacquer was shown as a decrease by 10°C of the glass transition temperature (Tg) for the lacquer on wood compared to the pure lacquer. The lacquer also demonstrated good adhesion to wood at a microscale. The interaction was investigated with dynamic mechanical thermal analysis and scanning electron microscopy fractography. The reason for the decrease in Tg is probably because of the lacquer having a higher free volume when applied to the wood, most likely due to it being subjected to tensile forces developed during the drying of the lacquer. Results from investigations of wood impregnated with two different acrylates, a polymethylmethacrylate and a more hydrophilic acrylate, support the suggestion that a decrease in Tg will occur if the polymer adheres to wood, but that poor interaction with little or no adhesion will result in no decrease in Tg. This article also presents results of the dynamic mechanical behavior of Scots Pine in the tangential direction

  • 3. Gebart, Rikard
    Critical parameters for heat transfer and chemical reactions in thermosetting materials1994In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 51, no 1, p. 153-168Article in journal (Refereed)
    Abstract [en]

    The equations of one-dimensional heat transfer with chemical reactions with isothermal initial conditions and constant wall temperature are solved approximately for all types of kinetic models. The general solution is valid for low exothermal peaks and it is characterized explicitly by two dimensionless parameters. The first parameter is the ratio between the time scale for heat conduction and that for the chemical reaction; the second parameter is the ratio between the processing temperature and the adiabatic temperature rise. The number of additional parameters depends on the particular choice of kinetic model. The maximum temperature in the solution always occur at the center line and its magnitude is proportional to the maximum rate of reaction. For a second-order autocatalytic kinetic model, closed form results can be obtained. The solution is in this case characterized by two additional dimensionless parameters. The analytical solution agrees excellently with numerical solutions for small exothermal temperature peaks (< 10% of the adiabatic temperature rise), but the qualitative agreement is very good also for cases with significant exothermal peaks. The general solution can be used also for the case when the kinetic model is unknown and only experimental DSC results are available.

  • 4.
    Haque, MD Minhaz Ul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Semi-IPN of biopolyurethane, benzyl starch, and cellulose nanofibers: Structure, thermal and mechanical properties2016In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 133, no 45, article id 43726Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to develop bionanocomposites of biopolyurethane (PU), benzyl starch (BS), and cellulose nanofibers (CNF) with semi-interpenetrating polymer network (S-IPN) structure of improved properties. Morphology, thermal and mechanical properties of S-IPN blends and nanocomposites were studied and compared with the neat polymers. Microscopy study showed that PU and BS were partially miscible as well as CNF were dispersed in both PU and BS phases in the nanocomposites. Dynamic mechanic thermal analysis demonstrated that BS decreased the tan δ peak of the PU while CNF increased it. The positive shifting of tan δ peak in the S-IPN nanocomposite also indicated the presence of CNF in the PU phase. It was also noticed that S-IPN nanocomposite displayed two tan δ peaks at higher temperature, indicating molecular interaction among BS, PU, and CNF. Furthermore, the S-IPN nanocomposites displayed significantly higher E-modulus and tensile strength compared with the neat PU

  • 5.
    Haque, Md. Minhaz-Ul
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Herrera, Natalia
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Geng, Shiyu
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Fibre and Particle Engineering, University of Oulu, Finland.
    Melt compounded nanocomposites with semi-interpenetrated network structure based on natural rubber, polyethylene, and carrot nanofibers2018In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 135, no 10, article id 45961Article in journal (Refereed)
    Abstract [en]

    The present study deals with the processing and characterization of cellulose nanocomposites natural rubber (NR), low-density polyethylene (LDPE) reinforced with carrot nanofibers (CNF) with the semi-interpenetrated network (S-IPN) structure. The nanocomposites were compounded using a co-rotating twin-screw extruder where a master-batch of NR and CNF was fed to the LDPE melt, and the NR phase was crosslinked with dicumyl peroxide. The prepared S-IPN nanocomposites exhibited a significant improvement in tensile modulus and yield strength with 5 wt % CNF content. These improvements are due to a better phase dispersion in the S-IPN nanocomposites compared with the normal blend materials, as demonstrated by optical microscopy, electron microscopy and ultraviolet–visible spectroscopy. The S-IPN nanocomposite also displayed an improved crystallinity and higher thermal resistance compared with NR, CNF, and the normal blend materials.

  • 6.
    Hassan, Mohammad L.
    et al.
    Cellulose and Paper Department, National Research Center, Dokki.
    Fadel, Shaimaa M.
    Cellulose and Paper Department, National Research Center, Dokki.
    El-Wakil, Nahla A.
    Cellulose and Paper Department, National Research Center, Dokki.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Chitosan/rice straw nanofibers nanocomposites: preparation, mechanical, and dynamic thermomechanical properties2012In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 125, no Suppl. 2, p. E216-E222Article in journal (Refereed)
    Abstract [en]

    Nanofibers were isolated from rice straw pulp using ultrahigh friction grinding and high-pressure homogenization. Chitosan nanocomposites were prepared using the isolated nanofibers at fiber loading from 2.5 to 20% by solution casting and evaporation technique. The effect of nanofiber loading on dry and wet tensile strength, dynamic mechanical thermal properties, and cyrstallinity of chitosan were studied using tensile testing, thermogravimetric analysis, dynamic mechanical thermal analysis, and X-ray diffraction. Addition of rice straw nanofibers (RSNF) to chitosan resulted in significant improvement in wet and dry tensile strength, and shift of glass transition temperature (Tg) of chitosan matrix to higher values. Chitosan nanocomposites prepared using RSNF (CRSNF) had remarkable wet and dry tensile strength, which could be attributed to presence of both nanofibers and nanosilica particles originally present in rice straw fibers. Addition of RSNF to chitosan did not affect its onset thermal degradation temperature

  • 7.
    Hedmark, Per G.
    et al.
    Kungliga tekniska högskolan, KTH.
    Jansson, Jan-Fredrik
    Kungliga tekniska högskolan, KTH.
    Hult, Anders
    Kungliga tekniska högskolan, KTH.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Gedde, Ulf W.
    Luleå tekniska universitet.
    Selective etching of thermotropic liquid crystalline polyesters1987In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 34, no 2, p. 743-762Article in journal (Refereed)
    Abstract [en]

    DSC, IR, ESCA, macroscopic etching rate measurements, analysis of etchant solution, and electron microscopy conclusively show that n-alkylamines (ethylamine, n-propylamine, n-butylamine, and n-pentylamine) and NaOH selectively degrade (etch) the ethylene terephthalate (ET)-rich phase in glassy liquid crystalline poly(p-hydroxybenzoic acid-co-ethylene terephthalate) [P(HBA-ET)] with molar compositions 0.60:0.40 and 0.80:0.20. ESCA demonstrates the excellent selectivity of the n-alkylamine etchants in the 0.60:0.40 copolymer. The 50 Å top layer of the etched samples contains 95 mol% HBA. Treatment with H2SO4 and NH3 gives ambiguous results, and these compounds are not suitable as etchants. It is demonstrated by electron microscopy on the 0.60:0.40 copolymer, in accordance with earlier reports by Joseph et al.,5-8 that the ET-rich phase is discontinuous (1-2 m spheres) and surrounded by an HBA-rich matrix. SEM is a useful tool for characterization of this morphology. However, both phases have a substracture which is revealed only by TEM. The morphology of the 0.80:0.20 copolymer is fine-textured, which means that SEM is a less suitable method for the characterization of etched samples.

  • 8. Hietala, Maiju
    et al.
    Rollo, Pierre
    LTU.
    Kekäläinen, Kaarina
    Fibre and Particle Engineering Laboratory, Department of Process and Environmental Engineering, University of Oulu.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Extrusion processing of green biocomposites: Compounding, fibrillation efficiency, and fiber dispersion2014In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 6Article in journal (Refereed)
    Abstract [en]

    The efficiency of twin-screw extrusion process to fibrillate cellulose fibers into micro/nanosize in the same step as the compounding of green bionanocomposites of thermoplastic starch (TPS) with 10 wt % fibers was examined. The effect of the processing setup on micro/nanofibrillation and fiber dispersion/distribution in starch was studied using two types of cellulose fibers: bleached wood fibers and TEMPO-oxidized cellulose fibers. A composite with cellulose nanofibers was prepared to examine the nanofiber distribution and dispersion in the starch and to compare the properties with the composites containing cellulose fibers. Optical microscopy, scanning electron microscopy, and UV/Vis spectroscopy showed that fibers were not nanofibrillated in the extrusion, but good dispersion and distribution of fibers in the starch matrix was obtained. The addition of cellulose fibers enhanced the mechanical properties of the TPS. Moisture uptake study revealed that the material containing TEMPO-oxidized fibers had higher moisture absorption than the other composites

  • 9. Jackson-Etang, Ayuk
    et al.
    Mathew, Aji P.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    The effect of plasticizer and cellulose nanowhisker content on the dispersion and properties of cellulose acetate butyrate nanocomposites2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 114, no 5, p. 2723-2730Article in journal (Refereed)
    Abstract [en]

    We studied the effects of plasticizer and cellulose nanowhisker content on the dispersion and properties of cellulose acetate butyrate (CAB)-based bionanocomposites. The cellulose nanowhiskers in an aqueous medium were solvent-exchanged to nonaqueous polar solvent (acetone) and used for nanocomposite processing by solution casting. The plasticized and unplasticized nanocomposites with 5 and 10 wt % cellulose nanowhisker content were prepared. Atomic force microscopy indicated nanoscale dispersion of whiskers in the CAB matrix. The dynamic mechanical analysis showed an increase in storage modulus with addition of cellulose nanowhiskers, especially above the glassy-rubbery transition region. Thermogravimetric analysis showed an improvement in thermal stability with increased whisker content for both unplasticized and plasticized nanocomposites. The plasticized nanocomposites showed better transparency than the unplasticized composites, indicating a better dispersion of cellulose nanowhiskers in CAB, in the presence of a plasticizer. The dynamic mechanical properties and thermal stability increased, whereas transparency decreased with increased CNW content.

  • 10.
    John, Maya Jacob
    et al.
    CSIR, Materials Science and Manufacturing, Polymers and Composites, Port Elizabeth.
    Anandjiwala, Rajesh
    CSIR, Materials Science and Manufacturing, Polymers and Composites, Port Elizabeth.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Melt-spun polylactic acid fibers: Effect of cellulose nanowhiskers on processing and properties2013In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 127, no 1, p. 274-281Article in journal (Refereed)
    Abstract [en]

    Bio-based continuous fibers were processed from polylactic acid (PLA) and cellulose nanowhiskers (CNWs) by melt spinning. Melt compounding of master batches of PLA with 10 wt % CNWs and pure PLA was carried out using a twin-screw extruder in which compounded pellets containing 1 and 3 wt % of CNWs were generated for subsequent melt spinning. The microscopy studies showed that the fiber diameters were in the range of 90-95 µm, and an increased surface roughness and aggregations in the fibers containing CNWs could be detected. The addition of the CNWs restricted the drawability of the fibers to a factor of 2 and did not affect the fiber stiffness or strength, but resulted in a significantly lower strain and slightly increased crystallinity. Furthermore, CNWs increased the thermal stability, creep resistance and reduction in thermal shrinkage of PLA fibers, possibly indicating a restriction of the polymer chain mobility due to the nanoscale additives.

  • 11.
    Kanelli, Maria
    et al.
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Douka, Aliki
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Vouyiouka, Stamatina
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Papaspyrides, Constatine D.
    Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens.
    Topakas, Evangelos
    BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens.
    Papaspyridi, Lefki-Maria
    National Technical University of Athens.
    Christakopoulos, Paul
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Production of biodegradable polyesters via enzymatic polymerization and solid state finishing2014In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 19, article id 40820Article in journal (Refereed)
    Abstract [en]

    The synthesis of aliphatic polyesters (PEs) derived from diols (1,4-butanediol and 1,8-octanediol) and diacids or their derivatives (diethyl succinate, sebacic acid, 1,12-dodecanedioic acid, and 1,14-tetradecanedioic acid) was achieved in order to produce poly(butylene succinate) (PE 4.4), poly(octylene sebacate) (PE 8.10), poly(octylene dodecanate) (PE 8.12), and poly(octylene tetradecanate) (PE 8.14). The herein suggested procedure involved two stages, both sustainable and in accordance with the principles of "green" polymerization. The first comprised an enzymatic prepolymerization under vacuum, in the presence of diphenylether as solvent using Candida antarctica lipase B as biocatalyst, whereas a low-temperature postpolymerization step [solid state polymerization (SSP)] followed in order to upgrade the PEs quality. In the enzymatically synthesized prepolymers, the range of number-average molecular weight attained was from 3700 to 8000 g/mol with yields reaching even 97%. Subsequently, SSP of PE 4.4 and 8.12 took place under vacuum or flowing nitrogen and lasted 10-48 h, at temperatures close to the prepolymer melting point (Tm -  TSSP varied between 4°C and 14°C). The solid state finishing led to increase in the molecular weight depending on the prepolymer type, and it also contributed to improvement of the physical characteristics and the thermal properties of the enzymatically synthesized PEs

  • 12.
    Keskisaari, Anna
    et al.
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Butylina, Svetlana
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Kärki, Timo
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Use of construction and demolition wastes as mineral fillers in hybrid wood-polymer composites2016In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 133, no 19, article id 43412Article in journal (Refereed)
    Abstract [en]

    The recycling of construction materials has been the subject of much research in past years. In this study, the use of construction and demolition wastes (CDWs) as mineral fillers in hybrid wood-polymer composites was studied. Two types of waste materials were used as fillers in the composites: (1) a mixture consisting of waste mineral wool (MW) and plasterboard (PB) and (2) mixed CDWs. The performance of the composites was evaluated from their mechanical properties and water-absorption behavior. We found in the study that the addition of mineral fillers decreased the flexural strength and modulus values of the wood-polypropylene (PP) composites. On the other hand, the exchange of part of the wood with a mineral filler resulted in an increase in the impact strength of the composite. The composite manufactured with the combination of MW and PB had the lowest water absorption. The decrease in wood loading resulted in improved dimensional stability in the hybrid wood-mineral filler-PP composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43412.

  • 13.
    Kornmann, Xavier
    et al.
    Luleå tekniska universitet.
    Thomann, Ralph
    Freiburg Materials Research Centre, Institute for Macromolecular Chemistry, Albert-Ludwigs-Universität.
    Mülhaupt, Rolf
    Freiburg Materials Research Centre, Institute for Macromolecular Chemistry, Albert-Ludwigs-Universität.
    Finter, Jürgen
    Vantico AG.
    Berglund, Lars
    Luleå tekniska universitet.
    Synthesis of amine-cured, epoxy-layered silicate nanocomposites: the influence of the silicate surface modification on the properties2002In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 86, no 10, p. 2643-2652Article in journal (Refereed)
    Abstract [en]

    Fluorohectorites were rendered organophilic through the cation exchange of sodium intergallery cations for protonated monoamine, diamine, and triamine oligopro-pyleneoxides and octadecylamine, benzylamine, and ad-ducts of octadecylamine and benzylamine with diglycidyl ether of bisphenol A (DGEBA). The influence of the silicate surface modification and compatibility on the morphology and thermal and mechanical properties was examined. Surface modification with protonated octadecylamine and its adduct with DGEBA promoted the formation of microscale domains of silicate layers separated by more than 50 A, as evidenced by transmission electron microscopy and wide-angle X-ray scattering. Young's modulus of these two nano-composites increased parabolically with the true silicate content, whereas conventionally filled composites exhibited a linear relationship. The highest fracture toughness was observed for conventionally filled composites.

  • 14.
    Lindhagen, Johan
    et al.
    Luleå tekniska universitet.
    Berglund, Lars A.
    Luleå tekniska universitet.
    Microscopical damage mechanisms in glass fiber reinforced polypropylene1998In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 69, no 7, p. 1319-1327Article in journal (Refereed)
    Abstract [en]

    The damage mechanisms in two structurally different glass mat reinforced polypropylene materials were studied. In situ microscopy was applied during the tensile testing of thin notched sheets. Micrographs of the damage processes in the two materials are presented. The major points of damage initiation were transversely oriented fibers and fiber bundles. In the swirled mat material, cracks grew along the fiber bundles; crack formation and growth was relatively unaffected by macroscopical stress concentration. In the short fiber material, crack growth occurred at the notch. In both materials the maximum load was determined by the fibers oriented in the longitudinal direction. The different damage mechanisms were interpreted in terms of damage zone size

  • 15.
    Liu, Xiaohui
    et al.
    Luleå tekniska universitet.
    Wu, Qiuju
    Luleå tekniska universitet.
    Berglund, Lars A.
    Luleå tekniska universitet.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Fan, Jiaqi
    State Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences.
    Zongneng, Qi
    State Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences.
    Polyamide 6/clay nanocomposites using a cointercalation organophilic clay via melt compounding2003In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 88, no 4, p. 953-958Article in journal (Refereed)
    Abstract [en]

    Polyamide 6/clay nanocomposites (PA6CN) were prepared via the melt compounding method by using a new kind of organophilic clay, which was obtained through cointercalation of epoxy resin and quaternary ammonium into Na-montmorillonite. The dispersion effect of this kind of organophilic clay in the matrix was studied by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM); the silicate layers were dispersed homogeneously and nearly exfoliated in the matrix. This was probably the result of the strong interaction between epoxy groups and amide end groups of PA6. The mechanical properties and heat distortion temperature (HDT) of PA6CN increased dramatically. The notched Izod impact strength of PA6CN was 80% higher than that of PA6 when the clay loading was 5 wt %. Even at 10 wt % clay content, the impact strength was still higher than that of PA6. The finely dispersed silicate layers and the strong interaction between silicate layers and matrix decreased the water absorption. At 10 wt % clay content, PA6CN only absorbs half the amount of water compared with PA6. The dynamic mechanical properties of PA6CN were also studied

  • 16. Mathew, Aji P.
    et al.
    Oksman, Kristiina
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Sain, Mohini
    University of Toronto.
    Mechanical properties of biodegradable composites from poly lactic acid (PLA) and microcrystalline cellulose (MCC)2005In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 97, no 5, p. 2014-2025Article in journal (Refereed)
    Abstract [en]

    Biodegradable composites were prepared using microcrystalline cellulose (MCC) as the reinforcement and polylactic acid (PLA) as a matrix. PLA is polyester of lactic acid and MCC is cellulose derived from high quality wood pulp by acid hydrolysis to remove the amorphous regions. The composites were prepared with different MCC contents, up to 25 wt %, and wood flour (WF) and wood pulp (WP) were used as reference materials. Generally, the MCC/PLA composites showed lower mechanical properties compared to the reference materials. The dynamic mechanical thermal analysis (DMTA) showed that the storage modulus was increased with the addition of MCC. The X-ray diffraction (XRD) studies on the materials showed that the composites were less crystalline than the pure components. However, the scanning electron microscopy (SEM) study of materials showed that the MCC was remaining as aggregates of crystalline cellulose fibrils, which explains the poor mechanical properties. Furthermore, the fracture surfaces of MCC composites were indicative of poor adhesion between MCC and the PLA matrix. Biodegradation studies in compost soil at 58°C showed that WF composites have better biodegradability compared to WP and MCC composites. The composite performances are expected to improve by separation of the cellulose aggregates to microfibrils and with improved adhesion

  • 17. Mathew, Aji P.
    et al.
    Thielemans, W.
    Ecole Française de Papeterie et des Industries Graphiques, Institut National Polytechique de Grenoble (EFPG-INGP).
    Dufresne, A.
    Centre de Recherches sur les Macromolécules Végétales (CERMAV-CNRS), Université Joseph Fourier.
    Mechanical properties of nanocomposites from sorbitol plasticized starch and tunicin whiskers2008In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 109, no 6, p. 4065-4074Article in journal (Refereed)
    Abstract [en]

    Nanocomposite materials were obtained using sorbitol plasticized waxy maize starch as matrix and tunicin whiskers as the reinforcement. The effect of filler load (0-25 wt % whiskers) and the relative humidity levels (0-98%) on the mechanical behavior of the films are discussed for linear and nonlinear deformation. The performance of the films is explained, based on the morphology and structural behavior of the composite materials (Mathew and Dufresne, Biomacromolecules 2002, 3, 609). The nanocomposites exhibit good mechanical strength due to the strong interaction between tunicin whiskers, matrix, plasticizer (sorbitol), and water, and due to the ability of the cellulose filler to form a rigid three-dimensional network. The evolution of Tg as a function of relative humidity level and filler load is studied in detail. A decrease in crystallinity of the amylopectin phase is observed at high filler loads, due to the resistance to chain rearrangement imposed by the whiskers. The mechanical strength increased proportionally with filler loads, showing an effective stress transfer from the matrix to the whiskers. An even distribution of whiskers (as determined by SEM) and plasticizer in the matrix contributes to the mechanical performance. The mechanical properties of the nanocomposites showed a strong dependence on relative humidity conditions

  • 18.
    Nikjoo, Dariush
    et al.
    Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar, Istanbul .
    Aroguz, Ayse
    Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar, Istanbul .
    Dual responsive polymeric bionanocomposite gel beads for controlled drug release systems2017In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 134, no 33, p. 45143-Article in journal (Refereed)
    Abstract [en]

    Scientists are searching potential solutions for cancer treatments as well as ways to avoid the side effects of anti-cancer agents, via targeted drug delivery. The aim of this research is to propose dual responsive beads based on sodium alginate (SA), methylcellulose (MC), and magnetic iron oxide nanoparticles (MIONs) for controlled release of 5-Fluorouracil (5-FU) as model drug. The beads were prepared by the dual crosslinking of SA and MC in the presence of MIONs. The structural, thermal, morphological, magnetic characteristics as well as the release profile of 5-FU were studied. The characterization results showed that the drug molecules and MIONs were well dispersed in the polymeric matrix. The cumulative release percentage was ca. 80% at pH = 4.2 and 40% at pH = 7.2 after 6 h. Thus, the sensitivity of beads on the pH value was verified. Moreover, the release profile exhibited reduction with an increase in the concentration of MIONs under an external magnetic field. The obtained results confirmed the dual sensitive release of 5-FU (i.e., PH/magnetic) that can be used for the targeted and controlled drug delivery systems.

  • 19.
    Norberg, Ida
    et al.
    Innventia AB, SE-114 86 Stockholm, Sweden.
    Nordström, Ylva
    Innventia AB, SE-114 86 Stockholm, Sweden.
    Drougge, Rickard
    Innventia AB, SE-114 86 Stockholm, Sweden.
    Gellerstedt, Göran
    Department of Fiber and Polymer Technology, Royal Institute of Technology - KTH.
    Sjöholm, Elisabeth
    Innventia AB, SE-114 86 Stockholm, Sweden.
    A new method for stabilization of softwood kraft lignin fibers for carbon fiber production2013In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 128, no 6, p. 3824-3830Article in journal (Refereed)
    Abstract [en]

    Renewable resources, such as kraft lignin, have shown great potential as precursors for carbon fiber production. This manuscript reports an investigation into the stabilization of softwood kraft lignin (SKL) fibers and the determination of the difference in stabilization between hardwood- and softwood-based kraft lignin fibers. The stabilization was achieved either thermally by using only heat or oxidatively in the presence of air, at various heating rates. A heating rate of 4°C min−1 and a holding time of 30 min at 250°C were successfully used for the thermal stabilization experiments. Faster stabilization was achieved using oxidative conditions at a heating rate of 15°C min−1 and 30 min holding time at 250°C. Furthermore, stabilization and carbonization in a one-step process was performed on SKL fibers, which show great potential to reduce both production time and costs. The stabilized and carbonized fibers were evaluated using thermal, spectroscopic, and microscopic methods

  • 20.
    Nordström, Ylva
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Joffe, Roberts
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sjöholm, Elisabeth
    Biorefinery Processes and Products, Innventia AB.
    Mechanical characterization and application of Weibull statistics to the strength of softwood lignin-based carbon fibers2013In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 130, no 5, p. 3689-3697Article in journal (Refereed)
    Abstract [en]

    Mechanical characterization of the first generation of softwood kraft lignin-based carbon fibers (CF) was carried out. The single fiber tensile tests of filaments with different diameters and length were performed to evaluate stiffness and strength of carbon fibers. The average mechanical properties were measured as follows: tensile strength of approximately 300 MPa, the elastic modulus of 30 GPa and a strain at failure within interval of 0.7-1.2%. The fiber strength data was evaluated by the two-parameter Weibull statistics and parameters of this distribution were obtained. Although strength of the produced fibers is still significantly lower than that of commercially available, the experimental results and predictions based on Weibull statistics show a fairly good fit.

  • 21.
    Nordström, Ylva
    et al.
    Innventia AB, SE-114 86 Stockholm, Sweden.
    Norberg, Ida
    Innventia AB, SE-114 86 Stockholm, Sweden.
    Sjöholm, Elisabeth
    Innventia AB, SE-114 86 Stockholm, Sweden.
    Drougge, Rickard
    Innventia AB, SE-114 86 Stockholm, Sweden.
    A new softening agent for melt spinning of softwood kraft lignin2013In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 129, no 3, p. 1274-1279Article in journal (Refereed)
    Abstract [en]

    Kraft lignin obtained from the pulping of wood is an interesting new precursor material for carbon fiber production because of its high carbon content and ready availability. However, continuous spinning of softwood kraft lignin (SKL) has been impossible because of its insufficient softening characteristics and neat hardwood kraft lignin (HKL) has required extensive pretreatments to enable fiber formation. Softwood kraft lignin permeate (SKLP) and hardwood kraft lignin permeate (HKLP), fractionated by membrane filtration, were continuously melt spun into fibers. To improve the spinnability of SKL and HKL, HKLP was added as a softening agent. SKL- and HKL-based fibers were obtained by adding 3–98 wt % HKLP. A suitable temperature range for spinning was 20–85°C above the Tg of the lignin samples, and this range gave a flawless appearance according to the SEM analysis. Smooth, homogeneous fibers of SKLP, HKLP, and SKL with HKLP were successfully processed into solid carbon fibers

  • 22.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Clemons, Craig
    Forest Products Laboratory.
    Mechanical properties and morphology of impact modified polypropylene-wood flour composites1998In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 67, no 9, p. 1503-1513Article in journal (Refereed)
    Abstract [en]

    The mechanical properties and morphology of polypropylene/wood flour (PP/WF) composites with different impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. Two different ethylene/propylene/diene terpolymers (EPDM) and one maleated styrene-ethylene/butylene-styrene triblock copolymer (SEBS-MA) have been used as impact modifiers in the PP/WF systems. All three elastomers increased the impact strength of the PP/WF composites but the addition of maleated EPDM and SEBS gave the greatest improvements in impact strength. Addition of MAPP did not affect the impact properties of the composites but had a positive effect on the composite unnotched impact strength when used together with elastomers. Tensile tests showed that MAPP had a negative effect on the elongation at break and a positive effect on tensile strength. The impact modifiers were found to decrease the stiffness of the composites. Scanning electron microscopy showed that maleated EPDM and SEBS had a stronger affinity for the wood surfaces than did the unmodified EPDM. The maleated elastomers are, therefore, expected to form a flexible interphase around the wood particles giving the composites better impact strength. MAPP further enhanced adhesion between WF and impact-modified PP systems. EPDM and EPDM-MA rubber domains were homogeneously dispersed in the PP matrix, the diameter of domains being between 0.1-1 m.

  • 23.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Influence of thermoplastic elastomers on adhesion in polyethylene-wood flour composites1998In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 68, no 11, p. 1845-1855Article in journal (Refereed)
    Abstract [en]

    The mechanical properties of recycled low-density polyethylene/wood flour (LDPE/WF) composites are improved when a maleated triblock copolymer styrene-ethylene/butylene-styrene (SEBS-MA) is added as a compatibilizer. The composites' tensile strength reached a maximum level with 4 wt% SEBS-MA content. The compatibilizer had a positive effect on the impact strength and elongation at break but decreased the composites' stiffness. Dynamic mechanical thermal analysis (DMTA), a lap shear adhesion test, and a scanning electron microscope (SEM) were used to investigate the nature of the interfacial adhesion between the WF/SEBS and between the WF/SEBS-MA. Tan δ peak temperatures for the various combinations showed interaction between the ethylene/butylene (EB) part of the copolymer and the wood flour in the maleated system. The shear lap test showed that adhesion between the wood and SEBS-MA is better than between the wood and SEBS. The electron microscopy study of the fracture surfaces confirmed good adhesion between the wood particles and the LDPE/SEBS-MA matrix.

  • 24.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lindberg, Henrik
    Luleå tekniska universitet.
    Holmgren, Allan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    The nature and location of SEBS-MA compatibilizer in polyethylene-wood flour composites1998In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 69, no 1, p. 201-209Article in journal (Refereed)
    Abstract [en]

    A maleic-anhydride-grafted styrene-ethylene - butylene-styrene (SEBS-MA) triblock copolymer has been used as a compatibilizer in low-density polyethylene-wood flour (LDPE-WF) composite system. The location of compatibilizer was studied using transmission electron microscopy (TEM). The unsaturated parts of the copolymer were stained with osmium tetraoxide (OsO4) to enhance contrast between the different phases. TEM micrographs indicated that part of the compatibilizer was located at the interface between the wood particles and PE matrix and that wood was also stained by the OsO4. The nature of the interface between the wood surface and the SEBS-MA was studied using Fourier transform infrared spectroscopy (FTIR). The results indicated that MA reacts with wood through esterification and hydrogen bonding and also possibly through interaction between the styrene and wood.

  • 25.
    Oksman, Kristiina
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Mathew, Aji P.
    Sain, Mohini
    University of Toronto.
    The effect of morphology and chemical characteristics of cellulose reinforcements on the crystallinity of polylactic acid2006In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 101, no 1, p. 300-310Article in journal (Refereed)
    Abstract [en]

    The aim of this work has been to study the crystallization behavior of composites based on polylactic acid (PLA) and three different types of cellulose reinforcements, viz., microcrystalline cellulose (MCC), cellulose fibers (CFs), and wood flour (WF). The primary interest was to determine how the size, chemical composition, and the surface topography of cellulosic materials affect the crystallization of PLA. The studied composite materials were compounded using a twin-screw extruder and injection-molded to test samples. The content of cellulose reinforcements were 25% by weight. The MCC and WF were shown to have a better nucleating ability than CFs based on differential scanning calorimetry and optical microscopy studies. It is difficult to visualize that transcrystallization will occur during melting process and this process is influenced by the morphological and chemical characteristics of the reinforcement. Bulk crystallization seems to be mainly dependent on the processing temperature. The cold crystallization process was shown to improve the thermal stability and storage modulus of the composites

  • 26.
    Oksman, Kristiina
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Wallström, Lennart
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Berglund, Lars A.
    Luleå tekniska universitet.
    Filho, Romildo Dias Toledo
    Federal University of Rio de Janeiro.
    Morphology and mechanical properties of unidirectional sisal-epoxy composites2002In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 84, no 13, p. 2358-2365Article in journal (Refereed)
    Abstract [en]

    Plant fibers are of increasing interest for use in composite materials. They are renewable resources and waste management is easier than with glass fibers. In the present study, longitudinal stiffness and strength as well as morphology of unidirectional sisal-epoxy composites manufactured by resin transfer molding (RTM) were studied. Horseshoe-shaped sisal fiber bundles (technical fibers) were nonuniformly distributed in the matrix. In contrast to many wood composites, lumen was not filled by polymer matrix. Technical sisal fibers showed higher effective modulus when included in the composite material than in the technical fiber test (40 GPa as compared with 24 GPa). In contrast, the effective technical fiber strength in the composites was estimated to be around 400 MPa in comparison with a measured technical fiber tensile strength of 550 MPa. Reasons for these phenomena are discussed

  • 27.
    Petersson, L.
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Oksman, Kristiina
    Mathew, Aji P.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Using maleic anhydride grafted poly(lactic acid) as a compatibilizer in poly(lactic acid)/layered-silicate nanocomposites2006In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 102, no 2, p. 1852-1862Article in journal (Refereed)
    Abstract [en]

    The goal of this work was to prepare exfoliated poly(lactic acid) (PLA)/layered-silicate nanocomposites with maleic anhydride grafted poly(lactic acid) (PLA-MA) as a compatibilizer. Two different layered silicates were used in the study: bentonite and hectorite. The nanocomposites were prepared by the incorporation of each layered silicate (5 wt %) into PLA via solution casting. X-ray diffraction of the prepared nanocomposites indicated exfoliation of the silicates. However, micrographs from transmission electron microscopy showed the presence of intercalated and partially exfoliated areas. Tensile testing showed improvements in both the tensile modulus and yield strength for all the prepared nanocomposites. The results from the dynamic mechanical thermal analysis showed an improvement in the storage modulus over the entire temperature range for both layered silicates together with a shift in the tan peak to higher temperatures. The effect of using PLA-MA differed between the two layered silicates because of a difference in the organic treatment. The bentonite layered silicate showed a more distinct improvement in exfoliation and an increase in the mechanical properties because of the addition of PLA-MA in comparison with the hectorite layered silicate

  • 28.
    Petersson, Linnea
    et al.
    Norwegian University of Science and Technology (NTNU), Trondheim.
    Mathew, Aji P.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Dispersion and properties of cellulose nanowhiskers and layered silicates in cellulose acetate butyrate nanocomposites2009In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 112, no 4, p. 2001-2009Article in journal (Refereed)
    Abstract [en]

    The aim of this work was to develop well dispersed nanocomposites, in a non water soluble polymer using a non aqueous, low polarity solvent as a dispersion medium. The nanoreinforcements were cellulose whiskers and layered silicates (LSs) and matrix was cellulose acetate butyrate (CAB). Before nanocomposite processing, a homogenizer was used in combination with sonification to achieve full dispersion of the nanoreinforcements in a medium of low polarity (ethanol). After processing, the cellulose nanowhiskers (CNW) showed flow birefringence in both ethanol and dissolved CAB, which indicated well dispersed whiskers. The microscopy studies indicated that the processing was successful for both nanocomposites. The CNW showed a homogeneous dispersion on nanoscale. The LS nanocomposite contained areas with lower degree of dispersion and separation of the LS sheets and formed mainly an intercalated structure. The produced materials were completely transparent, which indicated good dispersion. Transparency measurements also indicated that the nanocomposite containing CNW showed similar performance as the pure CAB. Dynamic mechanical thermal analysis (DMTA) showed improved storage modulus for a wide temperature range for both nanocomposites compared with the pure CAB matrix. This study indicated that CNW have a potential application in transparent nanocomposites based on fully renewable resources.

  • 29.
    PM, Visakh
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Thomas, Sabu
    Centre for Nanoscience and Nanotechnology, Mahatma Gandhi University, Kottayam, Kerala.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Cellulose nanofibres and cellulose nanowhiskers based natural rubber composites: Diffusion, sorption, and permeation of aromatic organic solvents2012In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 124, no 2, p. 1614-1623Article in journal (Refereed)
    Abstract [en]

    This article investigates the transport behavior of three aromatic organic solvents, viz. benzene, toluene, and p-xylene in natural rubber nanocomposite membranes containing cellulose nanofibres (CNFs) and cellulose nanowhiskers (CNWs) isolated from bamboo pulp. The solvent molecules act as molecular probes to study the diffusion, sorption, and permeation through the nanocomposites, and provide information on the nanocomposite structure and matrix-filler interactions. Both the nanocelluloses were found to decrease the uptake of aromatic solvents in nanocomposite membranes, but the effect was more significant in the case on nanofibers compared to nanowhiskers. Furthermore, the uptake decreased with increased penetrant size; being the highest for benzene and the lowest for p-xylene. Transport parameters such as diffusion coefficient, sorption coefficient, and permeation coefficient have been calculated. Comparison of the experimental values of equilibrium solvent uptake with the predicted values indicated that both the nanocelluloses have restricted the molecular mobility at the interphase and thereby decreased the transport of solvents through the materials; being more significant for nanofibers. The results showed that both the used cellulosic nanomaterials act as functional additives capable of manipulating and tailoring the transport of organic solvents through elastomeric membranes, even at concentrations as low as 2.5 wt %.

  • 30.
    Ranganathan, Nalini
    et al.
    Faculty of Forestry, University of Toronto.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nayak, Sanjay K.
    Central Institute of Plastics Engineering & Technology, TVK Industrial Estate, Guindy.
    Sain, Mohini
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Impact toughness, viscoelastic behavior, and morphology of polypropylene–jute–viscose hybrid composites2016In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 133, no 7, article id 42981Article in journal (Refereed)
    Abstract [en]

    In this investigation, we studied the impact toughness and viscoelastic behavior of polypropylene (PP)–jute composites. In this study, we used viscose fiber as an impact modifier and maleated PP as a compatibilizer. The toughness of the composites was studied with conventional Charpy and instrumental falling-weight impact tests. The composites' viscoelastic properties were studied with dynamic mechanical analysis. The results show that the incorporation of viscose fibers improved the impact strength and toughness to 134 and 65% compared to those of the PP–jute composites. The tan δ peak amplitude also increased with the addition of the impact modifier and indicated a greater degree of molecular mobility. The thermal stability of the composites was evaluated with thermogravimetric analysis. The addition of 2 wt % maleated polypropylene (MAPP) to the impact-modified composite improved the impact strength and toughness to 144 and 93%, respectively. The fiber–matrix morphology of the fracture surface and the Fourier transform infrared spectra were also studied to ascertain the existence of the type of interfacial bonds. Microstructural analysis showed the retention of viscose fibers in the composites compared to the more separated jute fibers

  • 31.
    Ranganathan, Nalini
    et al.
    Faculty of Forestry, University of Toronto.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nayak, Sanjay K
    Central Institute of Plastics Engineering and Technology, Chennai.
    Sain, Mohini
    Centre for Biocomposites and Biomaterials Processing, University of Toronto.
    Regenerated cellulose fibers as impact modifier in long jute fiber reinforced polypropylene composites: Effect on mechanical properties, morphology, and fiber breakage2015In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 132, no 3, article id 41301Article in journal (Refereed)
    Abstract [en]

    Polypropylene/jute fiber (PP-J) composites with various concentrations of viscose fibers (VF) as impact modifiers and maleated polypropylene (MAPP) as a compatibilizer have been studied. The composite materials were manufactured using direct long fiber thermoplastic (D-LFT) extrusion and compression molding. The effect of fiber length, after the extrusion process, on composites mechanical performance and toughness was investigated. The results showed that the incorporation of soft and tough VF on the PP-J improved the energy absorption of the composites. The higher impact strength was found with the addition of 10 wt % of the impact modifier, but the increased concentration of the impact modifier affected the tensile and flexural properties negatively. Similarly, HDT values were reduced with addition of viscose fibers whereas the addition of 2 wt % of maleated polypropylene significantly improved the overall composite properties. The microscopic analysis clearly demonstrated longer fiber pullouts on the optimized impact modified composite

  • 32.
    Skrifvars, Mikael
    et al.
    Neste Chemicals R&T.
    Berglund, Lars
    Luleå tekniska universitet.
    Ericson, Mats
    Luleå tekniska universitet.
    Microscopy of the morphology in low styrene emission glass fiber/unsaturated polyester laminates1999In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 71, no 10, p. 1555-1562Article in journal (Refereed)
    Abstract [en]

    Low styrene emission (LSE) unsaturated polyester resins are of interest in the context of increasing environmental concerns in the society. LSE resins have been developed to decrease styrene emission during the processing of composites based on unsaturated polyesters. In this article we applied a microscopy methodology to study morphology effects in laminates based on LSE polyesters. The study connects to the longer term objective to improve the understanding of how additives reduce styrene emission without imparting delamination resistance in composite laminates based on LSE polyesters. The major morphology differences between laminates made from different polyesters are discussed, including birefringent layers present as an interphase between different layers

  • 33.
    Tanpichai, Supachok
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Learning Institute, King Mongkut's University of Technology Thonburi, Bangkok; Nanotec–KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology Thonburi, Bangkok .
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Fibre and Particle Engineering, University of Oulu.
    Crosslinked poly(vinyl alcohol) composite films with cellulose nanocrystals: Mechanical and thermal properties2017In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 135, no 3, article id 45710Article in journal (Refereed)
    Abstract [en]

    In this work, poly(vinyl alcohol) (PVA) and cellulose nanocrystals (CNCs) were crosslinked using sodium tetraborate decahydrate (borax) to improve the mechanical and thermal properties of the neat PVA. The results showed that the CNCs affected the crystallization behavior of the crosslinked PVA. The crystallization temperature of the crosslinked PVA with CNCs increased considerably from ∼152 to ∼187 °C. The continuous improvement of the thermal stability was observed with the increasing content of CNCs in the crosslinked PVA films. Additionally, the strong interaction between the CNCs and PVA was theoretically estimated from the Young's modulus values of the composites. Thermodynamic mechanical testing revealed that the crosslinked PVA composite films with CNCs could bear higher loads at high temperature compared to the films without the CNCs. At 60 °C, 2.7 GPa was reported for the storage modulus of the crosslinked composites with 3 wt % of CNCs, twice as high as that for the crosslinked films without CNCs. Moreover, creep results were improved when CNCs were added in the crosslinked nanocomposites. The materials prepared in this work could broaden the opportunities for applications in a wide range of temperatures.

  • 34.
    Yuwawech, Kitti
    et al.
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Wootthikanokkhan, Jatuphorn
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Wanwong, Sompit
    Nanotec-KMUTT Center of Excellence on Hybrid Nanomaterials for Alternative Energy, King Mongkut's University of Technology (KMUTT)Thonburi, Bangkok .
    Tanpichai, Supachok
    School of EnergyEnvironment and Materials, King Mongkut's University of Technology Thonburi (KMUTT)Bangkok .
    Polyurethane/esterified cellulose nanocrystal composites as a transparent moisture barrier coating for encapsulation of dye sensitized solar cells2017In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 134, no 45, article id 45010Article in journal (Refereed)
    Abstract [en]

    This research work aims to investigate the effects of types and concentration of cellulose nanocrystals (CNCs) prepared from bacterial cellulose (BC) and nanofibrillated cellulose (NFC) on structure properties of polyurethane (PU) composites. Feasibility of applying the polymer composite for encapsulation of dye sensitized solar cells was of interest. Both CNCs were pretreated via esterification before mixing with the polyurethane by a solution process. Tensile strength and thermal stability of the PU/esterified CNCs were found to be superior to those of the systems reinforced with untreated CNCs. With the introduction of both untreated and esterified CNCs, water vapor transmission rates through the PU composite films were lowered while their visible light transmittance values were maintained to be above 80%. Also, better efficiency and stability of the solar cell were obtained when the PU was reinforced with CNCs, indicating its longer lifetime usage. The most suitable cell, described in terms of durability, was obtained when the PU was mixed with 2 wt % of esterified CNCs obtained from BC. Overall, this study shows that the surface modification of the CNCs is an important factor, affecting the reinforcing efficacy.

  • 35.
    Zhang, Yaolin
    et al.
    FPInnovations-Wood Products, Quebec City, Quebec.
    Wang, Xiang-Ming
    FPInnovations-Wood Products, Quebec City, Quebec.
    Casilla, Romulo Casilla
    FPInnovations-Wood Products, Vancouver, British Columbia.
    Cooper, Paul
    Faculty of Forestry, University of Toronto.
    Huang, Zeen
    Faculty of Forestry, University of Toronto.
    Wang, Xiaodong (Alice)
    Evaluation of block shear properties of selected extreme-PH structural adhesives by short term exposure test.2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 120, no 2, p. 657-665Article in journal (Refereed)
    Abstract [en]

    Nine structural adhesives with varying pH were selected to examine the effect of adhesive pH on wood–adhesive bond quality. The adhesives evaluated included four highly alkaline phenol–formaldehyde, one intermediate pH phenol–resorcinol–formaldehyde, two acidic melamine–urea–formaldehyde, and two acidic melamine–formaldehyde resins. Block shear specimens were prepared using Douglas-fir and black spruce wood. The adhesive performance was evaluated by measuring the shear properties (strength and wood failure) of the specimens tested at the dry and vacuum–pressure–redry (VPD) conditions. Adhesive pH, test condition, and wood species showed significant effects on shear properties. The different adhesives performed differently at the dry and VPD conditions. The high-pH adhesives (phenol–formaldehyde and phenol–resorcinol–formaldehyde) showed similar high wood failures at both test conditions and performed better than the low-pH adhesives (melamine–formaldehyde and melamine–urea–formaldehyde), especially after the VPD conditioning. The low-pH adhesives showed high wood failure at the dry condition, but wood failure decreased significantly after VPD conditioning for both species, indicating that the low-pH adhesives were less durable than the high-pH adhesives. High-pH adhesives did not have a negative impact on the strength of the bonded specimens.

  • 36.
    Zhang, Yaolin
    et al.
    FPInnovations–Forintek Division, Québec City.
    Wang, Xiang-Ming
    FPInnovations–Forintek Division, Québec City.
    Casilla, Romulo
    FPInnovations—Forintek Division, Vancouver BC.
    Cooper, Paul
    University of Toronto, Faculty of Forestry, Toronto, Ontario, Canada.
    Huang, Zeen
    University of Toronto, Faculty of Forestry, Toronto, Ontario, Canada.
    Wang, Xiaodong (Alice)
    Laurentian Forestry Centre, Canadian Forest Service, Quebec QC.
    Impact of Curing Condition on pH and Alkalinity/ Acidity of Structural Wood Adhesives2010In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 117, no 5, p. 2888-2898Article in journal (Refereed)
    Abstract [en]

    Nine formulations were selected for evalu- ating the effect of different curing methods on pH and alkalinity or acidity of various structural wood adhesives. These included four phenol–formaldehyde (PF) resins with high pH, one phenol–resorcinol–formaldehyde (PRF) resin with intermediate pH, two melamine–urea–formalde- hyde (MUF) resins, and two melamine–formaldehyde (MF) resins with low pH. The four curing methods used in the study were: (1) curing at 102–105C for 1 h (based on CSA O112.6-1977), (2) four-hour curing at 66C fol- lowed by 1-hour curing at 150C (based on ASTM D1583- 01), (3) curing at room temperature overnight (based on ASTM D 1583-01), and (4) cured adhesive squeezed out from glue lines of bonded shear block samples. The effect of the different methods on pH and alkalinity/acidity of the cured adhesive depended strongly on the individual adhesives. For the PF, the alkalinity was different for the different formulations in the liquid form, while in the cured form, the difference in the alkalinity depended on the curing method used. The MF and the MUF were the adhesives most affected by the method used. In particular, the MUF showed much higher cured film pH values when cured by method 2 compared to the other three methods, while both the cured MF and MUF exhibited quite variable acidity values when cured with the different methods. The PRF showed reasonably uniform cured film pH but varying acidity values when cured with the different methods.

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