Tenacificação e estabilidade foto-oxidativa de blendas compatibilizadas de poliestireno com resíduos de borracha.

Abstract

The aim of this research was to analyze the toughening and photo-oxidative stability of polystyrene (PS) blends with rubber residues (SBRr) in the footwear industry, compatible with 5, 7.5, and 10% of styrene-butadiene-styrene (SBS) and styreneethylene-butylene-styrene (SEBS) compatibilizers. The blends were prepared in a corotating twin screw extruder, after which the extruded pellets were injection-molded. The work consisted of two stages. In the first, the SBRr compound was evaluated for its chemical composition, particle size distribution, thermal analysis, morphology, and gel content. Subsequently, binary blends (PS with 20, 30, 40 and 50% of SBRr) were prepared to evaluate the effect of rubber residue concentration (SBRr) on impact strength. The PS/SBRr blend (50/50% by mass) was selected to study the effect of compatibilizer content because this blend demonstrated the highest impact strength. In the second stage, the mechanical behavior of the blends was evaluated in terms of photo-oxidative stability. The rheological results showed an increase in the viscosity of the blends, where the curves presented greater PS stability. As compatibilizer content increased, PS impact stregth increased significantly, especially with SBS; at 10% SBS, the impact strength reached 746%. However, the values of tensile, flexural, hardness, thermal deflection temperature (HDT) and Vicat softening properties were reduced when it comes to the PS. Therefore, these losses were comparatively less drastic given a high SBRr content and knowing that the residue is constituted of a complex mixture. When analyzing the influence of UV radiation on the tensile and impact properties of the blends, a considerable decrease was observed in the first 15 days, followed by a stabilization for up to 60 days. The presence of mineral fillers in the SBRr helped to reduce a drastic action of UV radiation and oxygen, thus minimizing major losses in mechanical properties. In general, the PS/SBRr blend containing 10% SBS presented a better balance of mechanical properties with and without photo-oxidation exposure.