The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
K E Evans - One of the best experts on this subject based on the ideXlab platform.
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the unusual thermal expansion behaviour of ptfe gf composites incorporating ptfe gf Recyclate
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: Oana Ghita, K E EvansAbstract:Abstract This study examines the thermal expansion behaviour of virgin and Recyclate polytetrafluoroethylene (PTFE)/glass fibre (GF) composites using two new sintering approaches – with and without pressure. In the case of composites sintered without pressure, the thermal expansion behaviour showed an unusual trace for both virgin and recycled samples. The introduction of a small amount glass fibre (
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effect of Recyclate ptfe gf laminate incorporation on the dielectric and mechanical properties of ptfe gf composites using a novel manufacturing process
Journal of Applied Polymer Science, 2011Co-Authors: Oana Ghita, K E EvansAbstract:This study examines the recycling of polytetrafluoroethylene (PTFE)/glass fiber (GF) printed circuit boards (PCB) laminates through mechanical grinding and the re-manufacture of new composites incorporating PTFE/GF Recyclate using sintering processes with and without pressure (SWOP and SWP). The PTFE/GF Recyclate was tested for mechanical and dielectric performance. Experimental data were fitted to modified Lichtenecker and Effective-Medium Theory (EMT) theoretical equations to estimate the dielectric constant of PTFE/GF Recyclate subsheets for further use in new PTFE/GF laminates. It was found that the experimental values were inside of the Wiener bounds and fitted well the two theories for both manufacturing methods proposed. Overall, the results showed that PTFE/GF Recyclate could be used as replacement for virgin PTFE/GF when incorporated in specific concentrations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
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successful closed loop recycling of thermoset composites
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: J Palmer, Luke Savage, Oana Ghita, K E EvansAbstract:This study investigates closed-loop thermoset composite recycling through grinding and reincorporation. Contrary to many other studies, it is shown that by careful attention to the separation and reformulation procedure, the mechanical integrity of recycled composites can be improved, and the use of substantially larger volumes of Recyclate is possible. Both factors are important aspects affecting the economic viability of regrinding as a possible future solution to the composites recycling problem.
Oana Ghita - One of the best experts on this subject based on the ideXlab platform.
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the unusual thermal expansion behaviour of ptfe gf composites incorporating ptfe gf Recyclate
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: Oana Ghita, K E EvansAbstract:Abstract This study examines the thermal expansion behaviour of virgin and Recyclate polytetrafluoroethylene (PTFE)/glass fibre (GF) composites using two new sintering approaches – with and without pressure. In the case of composites sintered without pressure, the thermal expansion behaviour showed an unusual trace for both virgin and recycled samples. The introduction of a small amount glass fibre (
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effect of Recyclate ptfe gf laminate incorporation on the dielectric and mechanical properties of ptfe gf composites using a novel manufacturing process
Journal of Applied Polymer Science, 2011Co-Authors: Oana Ghita, K E EvansAbstract:This study examines the recycling of polytetrafluoroethylene (PTFE)/glass fiber (GF) printed circuit boards (PCB) laminates through mechanical grinding and the re-manufacture of new composites incorporating PTFE/GF Recyclate using sintering processes with and without pressure (SWOP and SWP). The PTFE/GF Recyclate was tested for mechanical and dielectric performance. Experimental data were fitted to modified Lichtenecker and Effective-Medium Theory (EMT) theoretical equations to estimate the dielectric constant of PTFE/GF Recyclate subsheets for further use in new PTFE/GF laminates. It was found that the experimental values were inside of the Wiener bounds and fitted well the two theories for both manufacturing methods proposed. Overall, the results showed that PTFE/GF Recyclate could be used as replacement for virgin PTFE/GF when incorporated in specific concentrations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.
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Sheet moulding compound (SMC) from carbon fibre Recyclate
Composites Part A-applied Science and Manufacturing, 2010Co-Authors: J Palmer, Luke Savage, Oana Ghita, Kenneth E. EvansAbstract:This study reports on the first attempt to develop a new sheet moulding compound (SMC) using low cost carbon fibre (CF) Recyclate as the reinforcing component in place of conventional glass fibres. A newly designed manufacturing system allows large coarse Recyclate fibrous materials to be utilised within existing SMC production lines, and with careful control of virgin and Recyclate fibre distribution, a viable SMC grade utilising recycled CF can be obtained.
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successful closed loop recycling of thermoset composites
Composites Part A-applied Science and Manufacturing, 2009Co-Authors: J Palmer, Luke Savage, Oana Ghita, K E EvansAbstract:This study investigates closed-loop thermoset composite recycling through grinding and reincorporation. Contrary to many other studies, it is shown that by careful attention to the separation and reformulation procedure, the mechanical integrity of recycled composites can be improved, and the use of substantially larger volumes of Recyclate is possible. Both factors are important aspects affecting the economic viability of regrinding as a possible future solution to the composites recycling problem.
Roussel Xavier - One of the best experts on this subject based on the ideXlab platform.
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Enzymology of Sulfiredoxine, a sulfinyl reductase : characterization of the catalytic mechanism
2009Co-Authors: Roussel XavierAbstract:Les peroxyrédoxines à deux cystéines typiques (2-Cys Prx) sont impliquées dans la résistance des cellules au stress oxydant associé à H2O2, en réduisant H2O2 en H2O. En parallèle, ces enzymes participent à la transduction du signal dépendant de H2O2 en tant que second messager, via leur état rédox. La suroxydation sous forme d’acide sulfinique des 2-Cys Prx typiques eucaryotes est une modification posttraductionnelle qui inactive l’activité peroxydase, permettant de réguler le passage du message cellulaire H2O2-dépendant. La réduction de cette espèce oxydée est essentielle pour la viabilité des cellules. Cette réaction est catalysée par les sulfirédoxines (Srx). Les études réalisées ont permis de caractériser le mécanisme catalytique de Srx de S. cerevisiae qui consiste en : 1) l’activation de la fonction acide sulfinique sous forme d’anhydride phosphoryl sulfinique, par transfert direct du phosphate ? de l’ATP ; 2) la réduction de la fonction acide sulfinique activée par attaque de la Cys catalytique de Srx, ce qui conduit à un intermédiaire covalent thiosulfinate Prx/Srx ; 3) le recyclage de Srx avec la libération de PrxSOH. Au niveau du recyclage de l’activité Srx, deux classes de Srx peuvent être définies, celle à deux Cys et celle à une Cys. La classe de Srx à deux Cys, composée jusqu’à présent de Srx de levures, possède une Cys de recyclage qui attaque le thiosulfinate au niveau de la Cys de Srx, libérant la PrxSOH et la Srx oxydée sous forme de pont disulfure intramoléculaire. Cette forme oxydée de Srx est ensuite reconnue et réduite par la thiorédoxine. La classe de Srx à une Cys dont font partie les Srx de mammifères, ne possédant pas de Cys de recyclage, passe par un mécanisme de recyclage impliquant un réducteur autre que la Trx, qui reduit directement la fonction thiosulfinate, et dont la nature reste à déterminer.Typical two-cysteine peroxiredoxines are involved in cell resistance against H2O2-induced oxidative stress, by reducing H2O2 in H2O. Furthermore, these enzymes take part in H2O2 signalling, which is transmitted and regulated by their redox state. The eukaryotic typical 2-Cys Prxs are subject to post-translational modification under sulfinic acid oxidation state, which inactivates have lost their peroxidase activity and thus regulates allows the passage of H2O2-dependent cellular message. Reduction of the sulfinic acid oxidation state is essential for the cell viability. Sulfiredoxin (Srx) catalyzes this reduction. These research studies demonstrated that the catalytic mechanism of Srx occurs in three steps: first, the sulfinic acid is activated as a sulfinyl phosphoryl anhydride intermediate by a direct transfer of the ?-phosphate of ATP; second, the activated sulfinic acid intermediate is reduced via attack of the catalytic Cys of Srx, which leads to formation of a thiosulfinate intermediate and; third Srx, is recycled with concomitant release of the PrxSOH product of the reaction. Two classes of Srx could be defined depending on the mechanism of Srx recycling. The class comprising yeast Srxs have one recycling Cys. This Cys attacks the thiosulfinate intermediate, resulting in PrxSOH release and formation of an oxidized Srx intermediate. This oxidized species, with an intramolecular disulfide bond, is recognized and reduced by thioredoxin. In the class comprising Srx devoid of recycling Cys, which includes the mammalian Srxs, Srx is recycled by a reducer distinct from thioredoxin, which reduces directly the thiosulfinate function
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Enzymologie moléculaire d'une sulfinyl réductase, la sulfirédoxine : Caractérisation du mécanisme catalytique
HAL CCSD, 2009Co-Authors: Roussel XavierAbstract:Typical two-cysteine peroxiredoxines are involved in cell resistance against H2O2-induced oxidative stress, by reducing H2O2 in H2O. Furthermore, these enzymes take part in H2O2 signalling, which is transmitted and regulated by their redox state. The eukaryotic typical 2-Cys Prxs are subject to post-translational modification under sulfinic acid oxidation state, which inactivates have lost their peroxidase activity and thus regulates allows the passage of H2O2-dependent cellular message. Reduction of the sulfinic acid oxidation state is essential for the cell viability. Sulfiredoxin (Srx) catalyzes this reduction. These research studies demonstrated that the catalytic mechanism of Srx occurs in three steps: first, the sulfinic acid is activated as a sulfinyl phosphoryl anhydride intermediate by a direct transfer of the ?-phosphate of ATP; second, the activated sulfinic acid intermediate is reduced via attack of the catalytic Cys of Srx, which leads to formation of a thiosulfinate intermediate and; third Srx, is recycled with concomitant release of the PrxSOH product of the reaction. Two classes of Srx could be defined depending on the mechanism of Srx recycling. The class comprising yeast Srxs have one recycling Cys. This Cys attacks the thiosulfinate intermediate, resulting in PrxSOH release and formation of an oxidized Srx intermediate. This oxidized species, with an intramolecular disulfide bond, is recognized and reduced by thioredoxin. In the class comprising Srx devoid of recycling Cys, which includes the mammalian Srxs, Srx is recycled by a reducer distinct from thioredoxin, which reduces directly the thiosulfinate function.Les peroxyrédoxines à deux cystéines typiques (2-Cys Prx) sont impliquées dans la résistance des cellules au stress oxydant associé à H2O2, en réduisant H2O2 en H2O. En parallèle, ces enzymes participent à la transduction du signal dépendant de H2O2 en tant que second messager, via leur état rédox. La suroxydation sous forme d'acide sulfinique des 2-Cys Prx typiques eucaryotes est une modification posttraductionnelle qui inactive l'activité peroxydase, permettant de réguler le passage du message cellulaire H2O2-dépendant. La réduction de cette espèce oxydée est essentielle pour la viabilité des cellules. Cette réaction est catalysée par les sulfirédoxines (Srx). Les études réalisées ont permis de caractériser le mécanisme catalytique de Srx de S. cerevisiae qui consiste en : 1) l'activation de la fonction acide sulfinique sous forme d?anhydride phosphoryl sulfinique, par transfert direct du phosphate y de l'ATP ; 2) la réduction de la fonction acide sulfinique activée par attaque de la Cys catalytique de Srx, ce qui conduit à un intermédiaire covalent thiosulfinate Prx/Srx ; 3) le recyclage de Srx avec la libération de PrxSOH. Au niveau du recyclage de l'activité Srx, deux classes de Srx peuvent être définies, celle à deux Cys et celle à une Cys. La classe de Srx à deux Cys, composée jusqu'à présent de Srx de levures, possède une Cys de recyclage qui attaque le thiosulfinate au niveau de la Cys de Srx, libérant la PrxSOH et la Srx oxydée sous forme de pont disulfure intramoléculaire. Cette forme oxydée de Srx est ensuite reconnue et réduite par la thiorédoxine. La classe de Srx à une Cys dont font partie les Srx de mammifères, ne possédant pas de Cys de recyclage, passe par un mécanisme de recyclage impliquant un réducteur autre que la Trx, qui reduit directement la fonction thiosulfinate, et dont la nature reste à déterminer
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Enzymologie moléculaire d'une sulfinyl réductase, la sulfirédoxine (Caractérisation du mécanisme catalytique)
2009Co-Authors: Roussel Xavier, Branlant Guy, Rahuel-clermont SophieAbstract:Les peroxyrédoxines à deux cystéines typiques (2-Cys Prx) sont impliquées dans la résistance des cellules au stress oxydant associé à H2O2, en réduisant H2O2 en H2O. En parallèle, ces enzymes participent à la transduction du signal dépendant de H2O2 en tant que second messager, via leur état rédox. La suroxydation sous forme d acide sulfinique des 2-Cys Prx typiques eucaryotes est une modification posttraductionnelle qui inactive l activité peroxydase, permettant de réguler le passage du message cellulaire H2O2-dépendant. La réduction de cette espèce oxydée est essentielle pour la viabilité des cellules. Cette réaction est catalysée par les sulfirédoxines (Srx). Les études réalisées ont permis de caractériser le mécanisme catalytique de Srx de S. cerevisiae qui consiste en : 1) l activation de la fonction acide sulfinique sous forme d anhydride phosphoryl sulfinique, par transfert direct du phosphate ? de l ATP ; 2) la réduction de la fonction acide sulfinique activée par attaque de la Cys catalytique de Srx, ce qui conduit à un intermédiaire covalent thiosulfinate Prx/Srx ; 3) le recyclage de Srx avec la libération de PrxSOH. Au niveau du recyclage de l activité Srx, deux classes de Srx peuvent être définies, celle à deux Cys et celle à une Cys. La classe de Srx à deux Cys, composée jusqu à présent de Srx de levures, possède une Cys de recyclage qui attaque le thiosulfinate au niveau de la Cys de Srx, libérant la PrxSOH et la Srx oxydée sous forme de pont disulfure intramoléculaire. Cette forme oxydée de Srx est ensuite reconnue et réduite par la thiorédoxine. La classe de Srx à une Cys dont font partie les Srx de mammifères, ne possédant pas de Cys de recyclage, passe par un mécanisme de recyclage impliquant un réducteur autre que la Trx, qui reduit directement la fonction thiosulfinate, et dont la nature reste à déterminer.Typical two-cysteine peroxiredoxines are involved in cell resistance against H2O2-induced oxidative stress, by reducing H2O2 in H2O. Furthermore, these enzymes take part in H2O2 signalling, which is transmitted and regulated by their redox state. The eukaryotic typical 2-Cys Prxs are subject to post-translational modification under sulfinic acid oxidation state, which inactivates have lost their peroxidase activity and thus regulates allows the passage of H2O2-dependent cellular message. Reduction of the sulfinic acid oxidation state is essential for the cell viability. Sulfiredoxin (Srx) catalyzes this reduction. These research studies demonstrated that the catalytic mechanism of Srx occurs in three steps: first, the sulfinic acid is activated as a sulfinyl phosphoryl anhydride intermediate by a direct transfer of the ?-phosphate of ATP; second, the activated sulfinic acid intermediate is reduced via attack of the catalytic Cys of Srx, which leads to formation of a thiosulfinate intermediate and; third Srx, is recycled with concomitant release of the PrxSOH product of the reaction. Two classes of Srx could be defined depending on the mechanism of Srx recycling. The class comprising yeast Srxs have one recycling Cys. This Cys attacks the thiosulfinate intermediate, resulting in PrxSOH release and formation of an oxidized Srx intermediate. This oxidized species, with an intramolecular disulfide bond, is recognized and reduced by thioredoxin. In the class comprising Srx devoid of recycling Cys, which includes the mammalian Srxs, Srx is recycled by a reducer distinct from thioredoxin, which reduces directly the thiosulfinate function.NANCY1-Bib. numérique (543959902) / SudocSudocFranceF
Andrea Buettner - One of the best experts on this subject based on the ideXlab platform.
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the challenge of deodorizing post consumer polypropylene packaging screening of the effect of washing color sorting and heat exposure
Resources Conservation and Recycling, 2021Co-Authors: Bianca Lok, Andrea Buettner, Eva Ortner, Miriam Strangl, Pascal BreunigAbstract:Abstract For promoting a sustainable end-of-life-management for plastic packaging, mechanical recycling of especially post-consumer plastic packaging waste constantly gains more attention. To fulfill both industrial and consumer demands, and to increase the recycled content in new applications, high-quality Recyclates are of prime importance. However, the odor contamination of post-consumer polyolefin Recyclates is not only limiting their application field but is also of concern for the recycling industry and plastic converters since odor emissions during processing might affect the workers’ well-being. As the development of targeted odor reduction strategies requires detailed insights into causative odorants, the present study addresses the odor characterization of different recycled post-consumer polypropylene from the packaging sector by coupling human sensory and comprehensive instrumental analyses. Thereby, the impact of different washing procedures and color sorting were evaluated in terms of their odor reduction potential. In contrast to color sorting, implementation of a hot water washing step led to a noteworthy odor reduction since intensity ratings declined from 7.4 to 4.0, albeit the odor intensity was still not comparable to the low odor level of investigated virgin polypropylene (intensity rating of 2.1). Moreover, a screening on heat-induced emissions of odorous contaminants inspired by a standard extrusion process was performed, revealing a greater emission of odorants in terms of both number and perceived intensities with increasing temperature.
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Exploring Odor Minimization in Post-Consumer Plastic Packaging Waste through the Use of Probiotic Bacteria
Sustainability, 2020Co-Authors: Bianca Lok, Andrea Buettner, Philipp Denk, Eva Ortner, Tanja FellAbstract:Plastic packaging represents a large proportion of the plastic consumption throughout the world. The negative environmental impact associated with plastic packaging waste can be in part abated by recycling plastics, and increasing numbers of regulatory frameworks are being adopted towards this goal. Despite recent advances in modern recycling technologies, the production of high-quality polyolefin Recyclates remains a challenge. Among other functional requirements, odor plays a crucial role in the acceptance of recycled packaging. This presents a challenge, as odor contamination in plastic packaging waste can stem from diverse sources, such as spoilage processes, and strongly depends on the quality of the post-consumer input material. The present study addressed this issue by exploring potential odor abatement of malodors in packaging waste through the use of probiotic bacteria. Specifically, probiotics were added to a mixed post-consumer plastic packaging waste fraction, which was subsequently evaluated using human sensory and gas chromatography–olfactometric analyses. A comparison of treated with untreated plastic waste fractions revealed significant sensory differences. Further structural elucidation of the causative odorants confirmed a reduction in malodorous microbial metabolites, although complete odor removal was not achieved. However, this environmentally friendly approach may represent an essential step towards overcoming the odor burden in post-consumer plastic packaging Recyclates.
Paul T. Mativenga - One of the best experts on this subject based on the ideXlab platform.
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high voltage fragmentation and mechanical recycling of glass fibre thermoset composite
Cirp Annals-manufacturing Technology, 2016Co-Authors: Paul T. Mativenga, Fadri Pestalozzi, Jack Howarth, Norshah Aizat Shuaib, Jorg WoidaskyAbstract:Abstract Global increase of composite waste urgently requires innovative recycling technology. The three dimensional cross-linked structure makes melting and remoulding of thermoset composite impossible. In this study, high voltage fragmentation, originally conceived for fracturing rocks was investigated as a potential process for composite recycling. It was then benchmarked against its competitor, mechanical recycling. The investigation covered effectiveness in separating composite phases, energy demand and Recyclate quality. The work is a new contribution to the performance evaluation of key technologies for rapid recycling glass fibre thermoset composites, a major challenge for manufacturing and end-of-life product waste.
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energy intensity and environmental analysis of mechanical recycling of carbon fibre composite
Journal of Cleaner Production, 2014Co-Authors: Jack Howarth, Sada S R Mareddy, Paul T. MativengaAbstract:Abstract The increased usage of composites in industry coupled with European Union restrictions on landfill disposal has resulted in an urgent need to develop resource efficient recycling technologies. The purpose of this work was to model the electrical energy requirements of milling as a recycling option for carbon fibre composite. By separating the contributions to the total energy required of the machine tool, material cutting energy and material removal rate, the energy demand of carbon fibre composite recycling can be theoretically calculated for any milling process. The model was validated experimentally by comparing the theoretical energy demand to the measured energy demand of an industrial scale milling machine. It was found that at a processing (recycling) rate of 10 kg/hr, the specific energy was significantly less than the embodied energy of virgin carbon fibre (2.03 MJ/kg compared to approximately 200 MJ/kg). Although the form of the Recyclate fibres (short, single filaments and bundles) was vastly different to their virgin equivalents (continuous tows), the energy difference highlights the potential environmental benefit of utilising Recyclate fibres in place of virgin ones in short fibre composites where mechanical performance is less critical. The relationship between specific energy of recycling and processing rate was also calculated, which highlighted that further energy savings can be achieved at higher processing rates. This work is fundamentally important to provide new data sets for Life Cycle Assessment in order to assess the potential environmental benefits of utilising Recyclate fibres.