Transformation of truck tire rubber waste into thermoplastic vulcanizates: influence of vulcanization systems and compatibilizers in copolyester blends

The primary aim of this research was to repurpose truck tire rubber waste (TTRW) to address significant environmental challenges associated with tire disposal. This was achieved by devulcanizing the waste rubber and transforming it into versatile thermoplastic vulcanizates (TPVs), offering a novel approach to waste valorization. Devulcanized rubber (DR) was first prepared using a mechano-chemical process to break sulfur crosslinks, restoring the rubber’s plasticity. Blends of dynamically cured DR and thermoplastic polyester elastomer (COPE) were then developed. Through experimental investigation, phenolic resin at 16 phr was identified as the optimal curing agent, providing the best curing conditions. This formulation resulted in the highest shear viscosity, facilitating the breakup of the vulcanizing DR phase into smaller domains, approximately 0.77 μm in size, which enhanced interfacial adhesion and mechanical properties such as tensile strength and durability. To further improve the DR/COPE blend, maleic anhydride (MA) was incorporated as a compatibilizer at an optimal loading of 5 wt% relative to DR. MA initially formed hydrogen bonds with COPE and subsequently reacted with the diene rubber in DR via free radical and Diels–Alder mechanisms. These interactions improved interfacial adhesion and promoted finer dispersion of DR domains within the COPE matrix, leading to a refined phase morphology with the smallest domain size of 0.29 μm. The result was enhanced rheological and mechanical properties, including increased tensile strength to 9.3 MPa, elongation at break of 135%, hardness (Shore A) of 75, along with greater elasticity and improved solvent resistance. This study demonstrates the potential of using devulcanized truck tire rubber waste to develop high-performance, sustainable materials for various technological applications.