Compósitos de poliestireno e poliestireno expandido reciclado reforçado com fibras de curauá : propriedades e degradação

Abstract

The use of vegetable fibers as a reinforcing filler in polymer composites is receiving increased attention because of the good properties obtained in the final material and they are able to substitute conventional fillers such as glass fibers. Associated with this, the use of post-consumer polymers in products with higher value aggregate has economic, social and environmental interest. In this regard, this study aims to evaluate the recycling of expanded polystyrene (EPS) to obtain composites with the incorporation of curaua fiber. Virgin polystyrene composites (PS) reinforced with curaua fiber were initially developed considering the influence of the fiber content, the addition of coupling agent (based on anhydride maleic) and the effect of removing the shell fiber in order to select the best formulation. Expanded polystyrene from the central from the triage of the city of Caxias do Sul, was recycled into a device that consists of grinding and pass through screw heated to 100 °C, and the effects of this process in their morphological, thermal, mechanical and rheological properties were evaluated. The formulation previously selected to the PS matrix was used for the recycled polystyrene (rEPS) matrix. The composites were obtained using a pre-mixing in a single-screw extruder, followed by a twin-screw extruder and injection molding. The composites were evaluated in relation to their morphology (SEM), identification of functional groups (FTIR), mechanical strength (tensile and impact), thermal behavior (TGA and HDT), rheological (viscosity and melt flow index) and degradation in simulated soil and under UV radiation. The results showed that the recycling of EPS has no significant influence the material properties in comparison with the PS used as reference, thus enabling recycling process employed. Best properties were obtained for composite with virgin matrix using 20wt% curaua fiber shelled, containing 2wt% of coupling agent. With the use the recycled matrix noted a decrease in tensile strength compared to virgin matrix composite, since the other properties (impact strength, TGA, HDT and rheology) the composites with recycled matrix showed superior properties. The morphology of the composite was similar for virgin and recycled matrices, but in the presence of coupling agent it was possible to see more interaction fiber/matrix using the virgin matrix. In the biodegradability test in simulated soil and under UV radiation it was found that the presence of fiber, together with the coupling agent, did not prevent the degradation of the material, characterized by the presence of bands in the region of the carbonyl in the FTIR spectrum. However, morphological analysis was not observed crack formation, fissures and biofilm in the samples subjected to biodegradation in soil, however, at cracks were observed in the UV aging, this effect was less pronounced in the presence of coupling agent. In both trials of degradation was found that the presence of curaua fiber retards the degradation of the matrices when evaluated by measuring tensile strength. It was found that the recycling of EPS enables their use in obtaining vegetable fiber composite, reducing the environmental impact created disposal. Additionally it was proved that composite fiber curaua reinforced polystyrene has good properties and can be used as an engineering material.