6 research outputs found
Recycling of polyurethanes: where we are and where we are going
No full textPolyurethanes (PUs) represent a family of useful synthetic polymers (thermoplastic or thermosetting) obtained from diisocyanates and diols/polyols via polycondensation reactions. Within the circular economy concept and also considering the current need for limiting the environmental impact of plastics, several methods have been designed, assessed, and exploited for the recovery at the end-of-life of polyurethanes and for their recycling. Indeed, the processing of polyurethane wastes can be significantly beneficial not only from an ecological but also from an economic point of view. At present, feedstock (namely, glycolysis) and mechanical recycling are the two most important strategies to recover and recycle polyurethanes; notwithstanding, “biological recycling”, an approach that exploits the biological degradation of the polymer, is gaining interest. This review aims to elucidate the recycling processes of both thermoplastic and thermosetting polyurethanes, providing the reader with some perspectives about their possible future developments
Investigation and Optimization of Vacuum Plasma Treatment of PA66 Fabric for Reduced Fire Retardant Consumption
No full textFlame retardant (FR) textiles were obtained by surface treatments of polyamide 66 fabrics with microwave (MW) plasma technology in order to reduce the amount of FR involved in the fabric finishing process. More specifically, MW vacuum plasma was employed for polymer surface activation by using a helium/oxygen (He/O2) gas mixture, evaluating the effect of different treatment parameters on the affinity toward thiourea impregnation. Surface fabric modification was investigated both in terms of uniformity and increased thiourea absorption by infrared spectroscopy, wicking properties, and gravimetric characterization to define an operative window for plasma treatment conditions. According to the results obtained, the dry add-on content of thiourea improved up to 38%, thanks to the increase of the fabric surface activation. The effectiveness of plasma treatment resulted in an absolute increase up to 2% in limiting oxygen index (LOI) performance with respect to untreated fabric. As a consequence, a drastic reduction of 50% in thiourea concentration was required to achieve a similar fire retardant performance for plasma-treated fabric. On the basis of these preliminary results, a design of experiment (DoE) methodology was applied to the selected parameters to build a suitable response surface, experimentally validated, and to identify optimized treatment conditions. At the end, a final LOI index up to 43% has been reached
IMPROVEMENT OF FIRE BEHAVIOUR OF PA6 AND GLASS FIBER REINFORCED PA6 WITH HALOGEN-FREE ADDITIVES
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Predictive Tools to Assist the Development of Flame Retarded Phosphorus-Free Polypropylene and Identify Synergy between Flame Retardants
No full textThe development of flame-retarded polypropylene is carried out with the ultimate goal of obtaining a UL94-V0 not only halogen- but also phosphorus-free formulation because phosphate rocks, precursors of phosphorus-based flame retardants, are recognized as critical raw materials within Europe. Different flame retardants (FRs) (melamine, phosphate ester, and radical generator) are used. A statistical approach is applied to predict UL94 behavior and develop optimized formulations in terms of cost, filler or phosphorus content. Models for most common "nondripping" as well as "nonflaming dripping" UL94-V0 behavior are proposed. The experimental validation has shown the reliability of the models proposed and their usefulness to assist and speed up the development of optimized formulations. The use of the models also gives insight into the interactions between flame retardants, thus suggesting if potential synergies take place, before studying the FRs system in details. Indeed, synergies between melamine and phosphate ester as well as melamine and radical generator are discovered. Thanks to these synergies that V0 rating can be achieved. A UL94-V0 formulation, comprising melamine and radical generator, is identified as the optimal halogen- and phosphorus-free formulation with a reduced filler content
Investigation and Optimization of Vacuum Plasma Treatment of PA66 Fabric for Reduced Fire Retardant Consumption
No full textFlame retardant (FR) textiles were obtained by surface treatments of polyamide 66 fabrics with microwave (MW) plasma technology in order to reduce the amount of FR involved in the fabric finishing process. More specifically, MW vacuum plasma was employed for polymer surface activation by using a helium/ oxygen (He/O2) gas mixture, evaluating the effect of different treatment parameters on the affinity toward thiourea impregnation. Surface fabric modification was investigated both in terms of uniformity and increased thiourea absorption by infrared spectros-copy, wicking properties, and gravimetric characterization to define an operative window for plasma treatment conditions. According to the results obtained, the dry add-on content of thiourea improved up to 38%, thanks to the increase of the fabric surface activation. The effectiveness of plasma treatment resulted in an absolute increase up to 2% in limiting oxygen index (LOI) performance with respect to untreated fabric. As a consequence, a drastic reduction of 50% in thiourea concentration was required to achieve a similar fire retardant performance for plasma-treated fabric. On the basis of these preliminary results, a design of experiment (DoE) methodology was applied to the selected parameters to build a suitable response surface, experimentally validated, and to identify optimized treatment conditions. At the end, a final LOI index up to 43% has been reached
Validação fatorial da escala de percepção do sistema normativo: uma proposta para analisar a transgressão social
No full textIn Argentina, like in the rest of Latin America, the perception of transgression and lack of institutional legitimacy are shared beliefs. This tendency to illegal practices corrodes the political, economic and social development of the country. The goals of this study are to validate the structure of the Normative System Perception Scale (EPSN, for its Spanish acronym) and to analyze the perception of the normative system functioning. The sample consisted of 508 Argentinean participants. A selfadministered questionnaire with the Normative System Perception Scale and socio-demographic data was designed. Results show a good goodness-of-fit of the model and the reliability coefficients indicated satisfactory levels of internal consistency (α = .89). The descriptive analysis showed that participants had a negative perception of the normative system performance. Also the findings exhibit that women have a more negative perspective of the normative system than men, and that participants ideologically positioned on the right are more critical than those who are positioned on the left.En Argentina, al igual que en el resto de América Latina, la percepción de la transgresión y la falta de legitimidad institucional son creencias compartidas. Además, la tendencia a realizar prácticas ilegales corroe el desarrollo político, económico y social de un país. Teniendo esto en cuenta, los objetivos del presente estudio fueron validar la estructura de la Escala de Percepción del Sistema Normativo (EPSN) y describir la percepción del funcionamiento del sistema normativo, con una muestra compuesta por 508 participantes argentinos. Para esto se diseñó un cuestionario autoadministrado con la escala EPSN y preguntas sobre datos sociodemográficos. Los resultados muestran una buena bondad de ajuste y coeficientes de fiabilidad que indican una consistencia interna satisfactoria (α = .89), y los análisis descriptivos dan cuenta de que los participantes presentan una percepción negativa del funcionamiento del sistema normativo y, específicamente, que las mujeres tienen una perspectiva más negativa del funcionamiento del sistema normativo que los hombres, y que los participantes posicionados ideológicamente a la derecha son más críticos que los de izquierda.Na Argentina, assim como em toda a América Latina, a percepção da transgressão e da falta de legitimidade institucional são crenças compartilhadas. Além disso, a tendência a realizar práticas ilegais corrói o desenvolvimento político, econômico e social de um país. Nesse sentido, os objetivos deste estudo foram validar a estrutura da Escala de Percepção do Sistema Normativo (EPSN) e descrever a percepção do funcionamento do sistema normativo, com uma amostra de 508 participantes argentinos. Para isso, desenhou-se um questionário autoadministrado com a escala EPSN e dados sociodemográficos. Os resultados mostram uma bondade de ajuste e coeficientes de confiabilidade que indicam uma consistência interna satisfatória (α=.89), e as análises descritivas evidenciam que os participantes têm uma percepção negativa do funcionamento do sistema normativo e, especificamente, que as mulheres têm uma perspectiva mais negativa do funcionamento do sistema normativo do que os homens; além disso, os participantes posicionados ideologicamente à direita são mais críticos que os posicionados à esquerda
