Study of rheological, thermal and mechanical behavior of reprocessed polyamide 6

The effect of reprocessing Polyamide 6 (PA6) has been studied in this article. To simulate recycled PA, we reprocessed virgin PA through five cycles. The PA 6 has undergone mechanical, thermal and rheological characterization after the various cycles of reprocessing in order to evaluate the corresponding properties and correlate them with the number of cycles undergone. In order to widen our injection simulation analysis by computer (CAE: Computer Aided Engineering) of these new materials, it was necessary to determine the viscosity using a mathematical model; in this case the Cross-WLF, to determine the relevant parameters. Our results show that tensile strength, elongation at break and hardness remain practically constant, while the charpy impact decreases as the number of reprocessing cycles increases. The effects of reprocessing on the material may decrease the rheological properties; specifically the viscosity of the material decreases with increasing processing cycles. The thermal properties are also influenced with the reprocessed material. The crystallinity increases and the degradation reaction will be advanced to increase the reprocessing cycle.Crespo Amorós, JE.; Parres, F.; Peydro, MA.; Navarro Vidal, R. (2013). Study of rheological, thermal and mechanical behavior of reprocessed polyamide 6. Polymer Engineering and Science. 53(4):679-688. doi:10.1002/pen.23307S679688534Su, K.-H., Lin, J.-H., & Lin, C.-C. (2007). Influence of reprocessing on the mechanical properties and structure of polyamide 6. Journal of Materials Processing Technology, 192-193, 532-538. doi:10.1016/j.jmatprotec.2007.04.056Bai, X., Isaac, D. H., & Smith, K. (2007). Reprocessing acrylonitrile–butadiene–styrene plastics: Structure–property relationships. Polymer Engineering & Science, 47(2), 120-130. doi:10.1002/pen.20681Bonardi, A., Cilloni, R., Paganuzzi, V., & Grizzuti, N. (2003). Effects of Degree of Recycling on the Rheology and Processability of Thermoplastic Polymers. Journal of Polymer Engineering, 23(2). doi:10.1515/polyeng.2003.23.2.79Dijkstra, D. J. (2009). Guidelines for rheological characterization of polyamide melts (IUPAC Technical Report). Pure and Applied Chemistry, 81(2), 339-349. doi:10.1351/pac-rep-08-07-22Pedroso, A. ., Mei, L. H. ., Agnelli, J. A. ., & Rosa, D. . (1999). Properties that characterize the propagation of cracks of recycled glass fiber reinforced polyamide 6. Polymer Testing, 18(3), 211-215. doi:10.1016/s0142-9418(98)00020-8Pedroso, A. G., Mei, L. H. I., Agnelli, J. A. M., & Rosa, D. S. (2002). The influence of the drying process time on the final properties of recycled glass fiber reinforced polyamide 6. Polymer Testing, 21(2), 229-232. doi:10.1016/s0142-9418(01)00074-5Lozano-González, M. J., Rodriguez-Hernandez, M. T., Gonzalez-De Los Santos, E. A., & Villalpando-Olmos, J. (2000). Physical-mechanical properties and morphological study on nylon-6 recycling by injection molding. Journal of Applied Polymer Science, 76(6), 851-858. doi:10.1002/(sici)1097-4628(20000509)76:63.0.co;2-dBernardo, C. A., Cunha, A. M., & Oliveira, M. J. (1996). The recycling of thermoplastics: Prediction of the properties of mixtures of virgin and reprocessed polyolefins. Polymer Engineering & Science, 36(4), 511-519. doi:10.1002/pen.10437Incarnato, L., Scarfato, P., & Acierno, D. (1999). Rheological and mechanical properties of recycled polypropylene. Polymer Engineering & Science, 39(4), 749-755. doi:10.1002/pen.11463Maspoch, M. L., Ferrando, H. E., & Velasco, J. I. (2003). Characterisation of filled and recycled PA6. Macromolecular Symposia, 194(1), 295-304. doi:10.1002/masy.200390096Navarro, R., Ferrándiz, S., López, J., & Seguí, V. J. (2008). The influence of polyethylene in the mechanical recycling of polyethylene terephtalate. Journal of Materials Processing Technology, 195(1-3), 110-116. doi:10.1016/j.jmatprotec.2007.04.126Cross, M. M. (1965). Rheology of non-Newtonian fluids: A new flow equation for pseudoplastic systems. Journal of Colloid Science, 20(5), 417-437. doi:10.1016/0095-8522(65)90022-xWilliams, M. L., Landel, R. F., & Ferry, J. D. (1955). The Temperature Dependence of Relaxation Mechanisms in Amorphous Polymers and Other Glass-forming Liquids. Journal of the American Chemical Society, 77(14), 3701-3707. doi:10.1021/ja01619a008Boronat, T., Segui, V. J., Peydro, M. A., & Reig, M. J. (2009). Influence of temperature and shear rate on the rheology and processability of reprocessed ABS in injection molding process. Journal of Materials Processing Technology, 209(5), 2735-2745. doi:10.1016/j.jmatprotec.2008.06.013Reig, M. J., Segui, V. J., Ferrandiz, S., & Zamanillo, J. D. (2007). AN EVALUATION OF PROCESSABILITY BY INJECTION MOLDING OF ABS/PC BLENDS OBTAINED FROM RECYCLED MATERIALS. Journal of Polymer Engineering, 27(1). doi:10.1515/polyeng.2007.27.1.29Reig, M. J., Segui, V. J., & Zamanillo, J. D. (2005). Rheological Behavior Modeling of Recycled ABS/PC Blends Applied to Injection Molding Process. Journal of Polymer Engineering, 25(5). doi:10.1515/polyeng.2005.25.5.435Fornes, T. D., & Paul, D. R. (2003). Crystallization behavior of nylon 6 nanocomposites. Polymer, 44(14), 3945-3961. doi:10.1016/s0032-3861(03)00344-

Case report : De novo pathogenic variant in WFS1 causes Wolfram-like syndrome debuting with congenital bilateral deafness

Background: Congenital deafness could be the first manifestation of a syndrome such as in Usher, Pendred, and Wolfram syndromes. Therefore, a genetic study is crucial in this deficiency to significantly improve its diagnostic efficiency, to predict the prognosis, to select the most adequate treatment required, and to anticipate the development of other associated clinical manifestations. Case presentation: We describe a young girl with bilateral congenital profound deafness, who initially received a single cochlear implant. The genetic study of her DNA using a custom-designed next-generation sequencing (NGS) panel detected a de novo pathogenic heterozygous variant in the WFS1 gene related to Wolfram-like syndrome, which is characterized by the presence of other symptoms such as optic atrophy. Due to this diagnosis, a second implant was placed after the optic atrophy onset. The speech audiometric results obtained with both implants indicate that this work successfully allows the patient to develop normal speech. Deterioration of the auditory nerves has not been observed. Conclusion: The next-generation sequencing technique allows a precise molecular diagnosis of diseases with high genetic heterogeneity, such as hereditary deafness, while this was the only symptom presented by the patient at the time of analysis. The NGS panel, in which genes responsible for both syndromic and non-syndromic hereditary deafness were included, was essential to reach the diagnosis in such a young patient. Early detection of the pathogenic variant in the WFS1 gene allowed us to anticipate the natural evolution of the disease and offer the most appropriate management to the patient

Oriented Au nanoplatelets on graphene promote Suzuki-Miyaura coupling with higher efficiency and different reactivity pattern than supported palladium

[EN] Facet 111 oriented Au nanoplatelets (20-40 nm wide, 3-4 nm height) grafted on graphene ((Au) over bar /fl-G) are about three orders of magnitude more efficient than Pd nanoparticles supported on graphene to promote Suzuki-Miyaura coupling. In contrast to Pd catalysis, it is shown here that the product yields in Suzuki-Miyaura coupling catalyzed by Au nanoparticles follow the order chlorobenzene > bromobenzene > iodobenzene. Kinetic studies show that this reactivity order is the result of the poisoning effect of halides for Au that is much higher for I- than Br- and much higher than for Cl-, due to adsorption. This strong iodide adsorption leading to Au catalyst deactivation was predicted by DFT calculations of Au clusters. (Au) over bar /fl-G are about one order of magnitude more efficient than small Au nanoparticles (4-6 nm) obtained by the polyol method supported on graphene. Our results can have impact in organic synthesis, showing the advantage of (Au) over bar /fl-G as catalyst for Suzuki-Miyaura couplings.ADM thanks University Grants Commission (UGC), New Delhi for the award of Assistant Professorship under its Faculty Recharge Programme. ADM also thanks Department of Science and Technology, India, for the financial support through Extra Mural Research funding (SB/FT/CS-166/2013) and the Generalidad Valenciana for financial aid supporting his stay at Valencia through the Prometeo programme. Financial support by the Spanish Ministry of Economy and Competitiveness (CTQ-2012-32315 and Severo Ochoa) and Generalidad Valenciana (Prometeo 2012-014) is gratefully acknowledged. The research leading to these results has received partial funding from the European Community's Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 228862.Candu, N.; Dhakshinamoorthy, A.; Apostol, N.; Teodorescu, C.; Corma Canós, A.; García Gómez, H.; Parvulescu, VI. (2017). Oriented Au nanoplatelets on graphene promote Suzuki-Miyaura coupling with higher efficiency and different reactivity pattern than supported palladium. Journal of Catalysis. 352:59-66. https://doi.org/10.1016/j.jcat.2017.04.034S596635

Embedding catalytic nanoparticles inside mesoporous structures with controlled porosity: Au@TiO2

The ability to produce catalytic nanoparticles with controlled properties is key to developing and producing heterogeneous catalysts with optimized activity and selectivity. No less important is to maximize the nanoparticle dispersion over high area supports maintaining their optimized properties. Here we detail a general procedure to produce heterogeneous catalysts containing a large surface area mesoporous support and highly dispersed catalytic nanoparticles with controlled properties. We exemplify the developed method using colloidal gold nanocrystals as the catalytically active phase and titanium oxide as the paradigmatic support. Our synthetic strategy is based on the growth of an inorganic organic hybrid mesoporous material from the surface of the colloidal nanocrystals. A variety of organic spacers allows tuning the final porosity of the support. The good accessibility of the active catalytic sites in these materials is demonstrated by high CO oxidation conversion values.The research was supported by the European Regional Development Funds and the Spanish MICINN projects CSD2009-00050, MAT2011-29020-C02-01 and Severo Ochoa Excellence Program SEV-2012-0267.Nafria, R.; Ramirez De La Piscina, P.; Homs, N.; Ramon Morante, J.; Cabot, A.; Díaz Morales, UM.; Corma Canós, A. (2013). Embedding catalytic nanoparticles inside mesoporous structures with controlled porosity: Au@TiO2. Journal of Materials Chemistry. 1(45):14170-14176. https://doi.org/10.1039/c3ta13346jS141701417614

North African Influences and Potential Bias in Case-Control Association Studies in the Spanish Population

BACKGROUND: Despite the limited genetic heterogeneity of Spanish populations, substantial evidences support that historical African influences have not affected them uniformly. Accounting for such population differences might be essential to reduce spurious results in association studies of genetic factors with disease. Using ancestry informative markers (AIMs), we aimed to measure the African influences in Spanish populations and to explore whether these might introduce statistical bias in population-based association studies. METHODOLOGY/PRINCIPAL FINDINGS: We genotyped 93 AIMs in Spanish (from the Canary Islands and the Iberian Peninsula) and Northwest Africans, and conducted population and individual-based clustering analyses along with reference data from the HapMap, HGDP-CEPH, and other sources. We found significant differences for the Northwest African influence among Spanish populations from as low as ≈ 5% in Spanish from the Iberian Peninsula to as much as ≈ 17% in Canary Islanders, whereas the sub-Saharan African influence was negligible. Strikingly, the Northwest African ancestry showed a wide inter-individual variation in Canary Islanders ranging from 0% to 96%, reflecting the violent way the Islands were conquered and colonized by the Spanish in the XV century. As a consequence, a comparison of allele frequencies between Spanish samples from the Iberian Peninsula and the Canary Islands evidenced an excess of markers with significant differences. However, the inflation of p-values for the differences was adequately controlled by correcting for genetic ancestry estimates derived from a reduced number of AIMs. CONCLUSIONS/SIGNIFICANCE: Although the African influences estimated might be biased due to marker ascertainment, these results confirm that Northwest African genetic footprints are recognizable nowadays in the Spanish populations, particularly in Canary Islanders, and that the uneven African influences existing in these populations might increase the risk for false positives in association studies. Adjusting for population stratification assessed with a few dozen AIMs would be sufficient to control this effect

Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes

[EN] The increasing environmental concern and promotion of “green processes” are forcing the substitution of traditional acid and base homogeneous catalysts by solid ones. Among these heterogeneous catalysts, zeolites and zeotypes can be considered as real “green” catalysts, due to their benign nature from an environmental point of view. The importance of these inorganic molecular sieves within the field of heterogeneous catalysis relies not only on their microporous structure and the related shape selectivity, but also on the flexibility of their chemical composition. Modification of the zeolite framework composition results in materials with acidic, basic or redox properties, whereas multifunctional catalysts can be obtained by introducing metals by ion exchange or impregnation procedures, that can catalyze hydrogenation–dehydrogenation reactions, and the number of commercial applications of zeolite based catalysts is continuously expanding. In this review we discuss determinant issues for the development of zeolite based catalysts, going from zeolite catalyst preparation up to their industrial application. Concerning the synthesis of microporous materials we present some of the new trends moving into larger pore structures or into organic free synthesis media procedures, thanks to the incorporation of novel organic templates or alternative framework elements, and to the use of high-throughput synthesis methods. Post-synthesis zeolite modification and final catalyst conformation for industrial use are briefly discussed. In a last section we give a thorough overview on the application of zeolites in industrial processes. Some of them are well established mature technologies, such as fluid catalytic cracking, hydrocracking or aromatics alkylation. Although the number of zeolite structures commercially used as heterogeneous catalysts in these fields is limited, the development of new catalysts is a continuous challenge due to the need for processing heavier feeds or for increasing the quality of the products. The application of zeolite based catalysts in the production of chemicals and fine chemicals is an emerging field, and will greatly depend on the discovery of new or known structures by alternative, lower cost, synthesis routes, and the fine tuning of their textural properties. Finally, biomass conversion and selective catalytic reduction for conversion of NOx are two active research fields, highlighting the interest in these potential industrial applications.The authors acknowledge financial support from Ministerio de Ciencia e Innovacion (project Consolider-Ingenio 2010 MULTICAT).Martínez Sánchez, MC.; Corma Canós, A. (2011). Inorganic molecular sieves: Preparation, modification and industrial application in catalytic processes. Coordination Chemistry Reviews. 255(13-14):1558-1580. doi:10.1016/j.ccr.2011.03.014S1558158025513-1