STUDY OF MECHANICAL BEHAVIOR OF REPROCESSING HIGH IMPACT POLYSTYRENE, RECOVERY WITH SEBS

Abstract

The effect of reprocessing High Impact Polystyrene (HIPS) has been studied in this paper. To simulate recycled HIPS, we reprocessed virgin HIPS through 5 cycles. The HIPS has been mechanically characterized after the various cycles of reprocessing in order to evaluate their corresponding properties and correlate them with the number of cycles undergone. Our results show that tensile strength increases, while lengthening at break decreased as the number of reprocessing cycles increases. 1. INTRODUCCTION High Impact Polystyrene is a thermoplastic formed in two phases: a styrene phase and a butadiene phase. Among the diverse applications of this material is its use in the manufacture of packaging materials. This type of product can be characterized as having a short life cycle, and consequently a huge quantity of domestic waste is generated, which must be dealt with to reduce environmental impact. The problems which arise in the recovery of polymer materials are basically the variations that occur in their properties, due to either thermic degradation or the presence of impurities. Many studies have been carried out on the degradation of polymers. Su (3) analyzed the influence of the reprocessing cycles on the mechanical properties of polyamide 6 (PA6). Su's work is relevant to our work because he carried out a study of mechanical and rheological properties, although it was with a different material. Su's work is interesting, but we do not consider that reprocessing the material 16 times is very useful, because other studies show that the loss of property occurs in the first 5 reprocessed. (2,8) Other authors, including Santana (8) in their work in 2002 and Soriano (3) have carried out similar studies on HIPS. Santana investigated the themo-mechanical properties of post- consumer HIPS (from disposable cups) through five consecutive injection moulding steps to simulating the recycling cycles. Santana states that tensile strength, modulus of elasticity and elongation at break properties of HIPS were slightly reduced, which indicate an effect of decreasing of molecular weight. Soriano analyzes influence of the number of processing cycles on the microstructure and macroscopic properties on a HIPS in coextruded sheet, maintaining a constant composition of 70 wt% of virgin HIPS and 30 wt% of recycled HIPS. On the other hand, Balard (6) analyzed the compatibility of polycarbonate (PC) with acrylonitrile-butadiene-styrene (ABS) using waste material from the electrical sector, reaching the conclusion that the composition range comprised between 10 and 20 wt% PC is most interesting in order to obtain an industrial material with balanced properties, for different reasons: firstly, mechanical ductile properties do not decrease. Secondly, processing conditions are similar to other styrenic derivatives and finally, this composition range reflects the generation ratio of these wastes which is close to 4:1 for ABS/PC. Finally, Navarro (7) and Garcia (1) analyzed mixtures of polymers with the aim of improving properties of the recovered material. Navarro, in his study of the influence of polyethylene (PE) on recycled polyethylene terephtalate (PET) analyzed, among other things, mechanical and rheological properties.