Structure and properties of blends based on vulcanized rubber waste and styrene–butadiene–styrene thermoplastic elastomer

The paper presents the characterization and processing of a post-consumer vulcanized rubber waste for use as a filler to obtain polymer composites with thermoplastic matrix based on styrene–butadiene–styrene block copolymer (SBS). The influence of methods to improve compatibility, such as physical modification of rubber waste or dynamic crosslinking and grafting, on the characteristics of the polymer composites obtained was analyzed. To determine the composition of the rubber waste, the acetonic extract and the amount of ash were determined, and a Burchfield test as well as an FTIR analysis were performed to identify the type of rubber. Based on the analyses performed, it was observed that the base elastomer in the rubber waste is styrene butadiene rubber (SBR). It was filled with silicon dioxide (SiO 2 ) and vulcanized with sulfur (S). The rubber waste was cryogenically milled. Mixtures based on thermoplastic elastomers such as styrene–butadiene–styrene block copolymers and milled vulcanized rubber waste (powder) were obtained using a Plasti-Corder Brabender internal mixer. Crosslinking and grafting were performed by a radical reaction mechanism, in dynamic regime, at temperatures of 135–165 °C and rotational speeds of 80 rpm, using di-2-tert-butylisopropyl benzene as crosslinking agent and trimethylolpropane trimethacrylate as crosslinking coagent. The specimens for characterizing the mixtures were made by compression on a laboratory electrical press. The samples were characterized from a structural point of view and the physical–mechanical properties were determined, in the normal state and after accelerated aging for 168 h at 70 °C. The obtained results indicate that the vulcanized rubber powder acted as an elastic filler, leading to an increase in the hardness and elasticity of the samples. Grafting and crosslinking in a dynamic mode shows a significant improvement in hardness, elasticity and tensile strength. The samples show good stability at accelerated aging.