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Kristiina Oksman - One of the best experts on this subject based on the ideXlab platform.
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Polylactic Acid polyurethane blend reinforced with cellulose nanocrystals with semi interpenetrating polymer network s ipn structure
European Polymer Journal, 2017Co-Authors: Kristiina Oksman, Jatin Sethi, Mirja Illikainen, Mohini SainAbstract:The aim of the current work was to prepare and characterize a cellulose nanocrystal reinforced semi-interpenetrated network (SIPN) derived from Polylactic Acid (PLA) and polyurethane (PU) polymers. ...
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plasticized Polylactic Acid cellulose nanocomposites prepared using melt extrusion and liquid feeding mechanical thermal and optical properties
Composites Science and Technology, 2015Co-Authors: Natalia Herrera, Aji P Mathew, Kristiina OksmanAbstract:Plasticized Polylactic Acid (PLA) and its nanocomposite based on cellulose nanofibers (CNF) and glycerol triacetate (GTA) were prepared using a co-rotating twin-screw extruder. GTA was used as a pl ...
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Polylactic Acid cellulose whisker nanocomposites modified by polyvinyl alcohol
Composites Part A-applied Science and Manufacturing, 2007Co-Authors: Daniel Bondeson, Kristiina OksmanAbstract:The aim of this study was to produce biodegradable Polylactic Acid/cellulose whisker nanocomposites by compounding extrusion and investigate the possibility to use polyvinyl alcohol to improve the dispersion of whiskers in the matrix. Two feeding methods of polyvinyl alcohol and cellulose nanowhiskers were used and evaluated, dry-mixing with Polylactic Acid prior extrusion or pumping as suspension directly into the extruder. Various microscopic techniques, tensile testing, and dynamic mechanical thermal analysis were used to study the structure and properties of the nanocomposites. Due to immiscibility of the polymers, phase separation occurred with a continuous Polylactic Acid phase and a discontinuous polyvinyl alcohol phase. The whiskers were primarily located in the polyvinyl alcohol phase and only a negligible amount was located in the Polylactic Acid phase. This inadequate dispersion of whiskers in the Polylactic Acid phase was probably the reason why no improvements in thermal properties were seen for the nanocomposites. The relative small improvements in tensile modulus, tensile strength, and elongation to break for the nanocomposites also indicated that it was principally the polyvinyl alcohol phase that was reinforced with whiskers but not the Polylactic Acid phase.
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manufacturing process of cellulose whiskers Polylactic Acid nanocomposites
Composites Science and Technology, 2006Co-Authors: Kristiina Oksman, Daniel Bondeson, Aji P Mathew, Ingvild KvienAbstract:Cellulose whiskers separated from commercially available microcrystalline cellulose (MCC) and Polylactic Acid (PLA) were used to develop novel nanostructured biocomposites by compounding extrusion. MCC was treated with N,N-dimethylacetamide (DMAc) containing lithium chloride (LiCl) in order to swell the MCC and partly separate the cellulose whiskers. The suspension of whiskers was pumped into the polymer melt during the extrusion process. Different microscopy techniques, thermogravimetric analysis, X-ray diffraction and mechanical testing were used to study the structure and properties of the whiskers and composites. The results showed that DMAc/LiCl can be used as swelling/separation agent for MCC but seems to cause degradation of the composites at high temperature processing. The structure of composites was made up of partly separated nanowhiskers when PEG was used as processing aid. The mechanical properties of nanocomposites were improved and compared to reference material the elongation to break was increased about 800% for one material combination. The future studies will be focused on process optimization, dispersion of nanowhiskers and finding a more suitable pumping medium to avoid thermal degradation of the composite.
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the effect of morphology and chemical characteristics of cellulose reinforcements on the crystallinity of Polylactic Acid
Journal of Applied Polymer Science, 2006Co-Authors: Aji P Mathew, Kristiina Oksman, Mohini SainAbstract: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 cellul ...
David Amiel - One of the best experts on this subject based on the ideXlab platform.
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cartilage repair with autogenic perichondrium cell and Polylactic Acid grafts
Clinical Orthopaedics and Related Research, 2000Co-Authors: Jon S Dounchis, Richard D Coutts, Albert C Chen, David AmielAbstract:The repair of articular cartilage injuries remains a challenge, with many of the current therapeutic strategies based on the grafting or recruitment of chondrogenic tissues or cells. This 1-year study compared the repair of a 3.7-mm diameter by 3-mm deep osteochondral defect in the medial femoral condyle of 24 New Zealand White rabbits; the defect was obtained using an autogenic perichondrium cell Polylactic Acid composite graft with a contralateral control in which the osteochondral defect remained empty. To elucidate the effect of host immune responses on the repair process after perichondrium cell transplantation, the results of the autogenic perichondrium cell Polylactic Acid graft group were compared with those obtained in the authors' previous 1-year study of allogenic perichondrium cell Polylactic Acid composite grafts implanted in a similar model. One year after surgery, the repair site underwent gross inspection and histologic, histomorphometric, biochemical, and biomechanical analyses. The autogenic perichondrium cell Polylactic Acid graft group (92%) and the control group in which the osteochondral defect remained empty (88%) resulted in a high percentage of grossly acceptable repairs. The autogenic grafts appeared to augment the intrinsic healing capacity of the animals (as compared with the animals in the No Implant Group). The autogenic perichondrium cell Polylactic Acid grafts improved the histologic appearance and percentage of Type II collagen of the cartilaginous repair tissue. Compared with allogenic grafts, the autogenic grafts had better reconstitution of the subchondral bone. However, the results of this experimental model suggest a suboptimal concentration of glycosaminoglycans in the neocartilage matrix, a depressed surface of the repair tissue, a histologic appearance that was not equivalent to that of normal articular cartilage, and reduced biomechanical properties for the repair tissue. The future application of growth factors to this model may yield a treatment that can be applied in the clinical arena.
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articular cartilage repair using allogeneic perichondrocyteseeded biodegradable porous Polylactic Acid pla a tissue engineering study
Journal of Biomedical Materials Research, 1995Co-Authors: Richard D Coutts, Anna Z Monosov, Frederick L Harwood, Makoto Yoshioka, David AmielAbstract:Efforts to expand treatment options for articular cartilage repair have increasingly focused on the implantation of cell-polymer constructs. The purpose of this study is to determine the suitability of porous D,D-L,L-Polylactic Acid as a carrier for delivering repair cells obtained from rib perichondrium into full-thickness articular cartilage defects. In vitro characterization of perichondrocyte-Polylactic Acid composite grafts was combined with in vivo assessment of the early articular cartilage repair in a clinically relevant model. Using a fluorescent double-stain protocol to visualize live and dead cells in situ, primary cells cultured from perichondrium were found to be capable of attaching to and surviving within a porous D,D-L,L-Polylactic Acid matrix. These perichondrocyte-Polylactic Acid composite grafts were then implanted within osteochondral defects drilled into the left medial femoral condyles of 16 adult New Zealand white rabbits. Experimental animals were sacrificed 6 weeks after implantation and the repair tissue was evaluated grossly, histologically, and biochemically. Grossly, 96% (15/16) of the experimental animals demonstrated repairs consisting of a smooth, firm neocartilage which appeared similar in color and texture to the surrounding articular surface. Matrix staining for cartilaginous protein was seen surrounding chondrocyte-like cells in the cartilage regions of the repair. Cellular alignment was found to be related to scaffold architecture. These results suggest that scaffolds composed of porous D,D-L,L-Polylactic Acid support the growth of cartilaginous repair tissue and are compatible with both in vitro and in vivo survival of chondrogenic cells.
Sergio I. Molina - One of the best experts on this subject based on the ideXlab platform.
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Development of Surface-Coated Polylactic Acid/Polyhydroxyalkanoate (PLA/PHA) Nanocomposites
Polymers, 2019Co-Authors: J. J. Relinque, A. S. De León, J. Hernández-saz, M. G. García-romero, Francisco J. Navas-martos, Gabriel Morales-cid, Sergio I. MolinaAbstract:This work reports on the design and development of nanocomposites based on a polymeric matrix containing biodegradable Polylactic Acid (PLA) and Polyhydroxyalkanoate (PHA) coated with either Graphite NanoPlatelets (GNP) or silver nanoparticles (AgNP). Nanocomposites were obtained by mechanical mixing under mild conditions and low load contents (
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Development of Surface-Coated Polylactic Acid/Polyhydroxyalkanoate (PLA/PHA) Nanocomposites
MDPI AG, 2019Co-Authors: J. J. Relinque, A. S. De León, J. Hernández-saz, M. G. García-romero, Francisco J. Navas-martos, Gabriel Morales-cid, Sergio I. MolinaAbstract:This work reports on the design and development of nanocomposites based on a polymeric matrix containing biodegradable Polylactic Acid (PLA) and Polyhydroxyalkanoate (PHA) coated with either Graphite NanoPlatelets (GNP) or silver nanoparticles (AgNP). Nanocomposites were obtained by mechanical mixing under mild conditions and low load contents (<0.10 wt %). This favours physical adhesion of the additives onto the polymer surface, while the polymeric bulk matrix remains unaffected. Nanocomposite characterisation was performed via optical and focused ion beam microscopy, proving these nanocomposites are selectively modified only on the surface, leaving bulk polymer unaffected. Processability of these materials was proven by the fabrication of samples via injection moulding and mechanical characterisation. Nanocomposites showed enhanced Young modulus and yield strength, as well as better thermal properties when compared with the unmodified polymer. In the case of AgNP coated nanocomposites, the surface was found to be optically active, as observed in the increase of the resolution of Raman spectra, acquired at least 10 times, proving these nanocomposites are promising candidates as surface enhanced Raman spectroscopy (SERS) substrates
Kim Pickering - One of the best experts on this subject based on the ideXlab platform.
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Fused Deposition Modelling of Natural Fibre/Polylactic Acid Composites
Journal of Composites Science, 2017Co-Authors: David Stoof, Kim PickeringAbstract:Fused deposition modelling is a simple additive manufacturing technology utilising fine filament extrusion of predominantly thermoplastic materials to build 3D objects layer by layer. This research explores the feasibility and the factors involved in using fused deposition modelling to produce natural fibre reinforced composite components. Uniform 3-mm filaments of both hemp and harakeke (Phormium tenax) in varying weight percentages within Polylactic Acid (PLA) polymer were successfully produced and used to print tensile test samples. Tensile test results supported harakeke to be a useful fibre in terms of mechanical properties achieved which surpassed the Young’s modulus and tensile strength of plain PLA samples by 42.3% and 5.4%, respectively.
Richard D Coutts - One of the best experts on this subject based on the ideXlab platform.
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cartilage repair with autogenic perichondrium cell and Polylactic Acid grafts
Clinical Orthopaedics and Related Research, 2000Co-Authors: Jon S Dounchis, Richard D Coutts, Albert C Chen, David AmielAbstract:The repair of articular cartilage injuries remains a challenge, with many of the current therapeutic strategies based on the grafting or recruitment of chondrogenic tissues or cells. This 1-year study compared the repair of a 3.7-mm diameter by 3-mm deep osteochondral defect in the medial femoral condyle of 24 New Zealand White rabbits; the defect was obtained using an autogenic perichondrium cell Polylactic Acid composite graft with a contralateral control in which the osteochondral defect remained empty. To elucidate the effect of host immune responses on the repair process after perichondrium cell transplantation, the results of the autogenic perichondrium cell Polylactic Acid graft group were compared with those obtained in the authors' previous 1-year study of allogenic perichondrium cell Polylactic Acid composite grafts implanted in a similar model. One year after surgery, the repair site underwent gross inspection and histologic, histomorphometric, biochemical, and biomechanical analyses. The autogenic perichondrium cell Polylactic Acid graft group (92%) and the control group in which the osteochondral defect remained empty (88%) resulted in a high percentage of grossly acceptable repairs. The autogenic grafts appeared to augment the intrinsic healing capacity of the animals (as compared with the animals in the No Implant Group). The autogenic perichondrium cell Polylactic Acid grafts improved the histologic appearance and percentage of Type II collagen of the cartilaginous repair tissue. Compared with allogenic grafts, the autogenic grafts had better reconstitution of the subchondral bone. However, the results of this experimental model suggest a suboptimal concentration of glycosaminoglycans in the neocartilage matrix, a depressed surface of the repair tissue, a histologic appearance that was not equivalent to that of normal articular cartilage, and reduced biomechanical properties for the repair tissue. The future application of growth factors to this model may yield a treatment that can be applied in the clinical arena.
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articular cartilage repair using allogeneic perichondrocyteseeded biodegradable porous Polylactic Acid pla a tissue engineering study
Journal of Biomedical Materials Research, 1995Co-Authors: Richard D Coutts, Anna Z Monosov, Frederick L Harwood, Makoto Yoshioka, David AmielAbstract:Efforts to expand treatment options for articular cartilage repair have increasingly focused on the implantation of cell-polymer constructs. The purpose of this study is to determine the suitability of porous D,D-L,L-Polylactic Acid as a carrier for delivering repair cells obtained from rib perichondrium into full-thickness articular cartilage defects. In vitro characterization of perichondrocyte-Polylactic Acid composite grafts was combined with in vivo assessment of the early articular cartilage repair in a clinically relevant model. Using a fluorescent double-stain protocol to visualize live and dead cells in situ, primary cells cultured from perichondrium were found to be capable of attaching to and surviving within a porous D,D-L,L-Polylactic Acid matrix. These perichondrocyte-Polylactic Acid composite grafts were then implanted within osteochondral defects drilled into the left medial femoral condyles of 16 adult New Zealand white rabbits. Experimental animals were sacrificed 6 weeks after implantation and the repair tissue was evaluated grossly, histologically, and biochemically. Grossly, 96% (15/16) of the experimental animals demonstrated repairs consisting of a smooth, firm neocartilage which appeared similar in color and texture to the surrounding articular surface. Matrix staining for cartilaginous protein was seen surrounding chondrocyte-like cells in the cartilage regions of the repair. Cellular alignment was found to be related to scaffold architecture. These results suggest that scaffolds composed of porous D,D-L,L-Polylactic Acid support the growth of cartilaginous repair tissue and are compatible with both in vitro and in vivo survival of chondrogenic cells.