Toward the reuse of styrene-butadiene (SBRr) waste from the shoes industry: production and compatibilization of BioPE/SBRr blends

The postconsumer waste of vulcanized styrene-butadiene rubber (SBRr) is a raw material rich in additives with potential reuse in the plastics processing industry. The present investigation evaluated the effectiveness of styrene-ethylene/butylene-styrene copolymer (SEBS) in the compatibilization of biopolyethylene (BioPE)/SBRr blends. The blends were processed in a twin-screw extruder and injection molded to evaluate the melt flow index (MFI), impact strength, tensile strength, Shore D hardness, thermogravimetry (TG), differential scanning calorimetry (DSC), and heat deflection temperature (HDT). Morphology was studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The BioPE/SBRr/SEBS blend (70/20/10 wt%) showed the lowest MFI, which indicates a higher viscosity and, consequently, higher compatibility that led to increments of 120% and 698.6% on impact strength and elongation at break, respectively, compared to the noncompatibilized system. The reduction in elastic modulus, tensile strength, and Shore D hardness confirmed the increased flexibility of the BioPE/SBRr/SEBS blends. Melting and crystallization properties of the polymer blends were comparable to the BioPE matrix, suggesting that 20 wt% SBRr content did not severely deteriorate the thermal behavior. SEM analysis showed that SEBS induced a morphology with extensive plastic deformation, confirming the high impact strength and elongation at break. BioPE/SBRr blends compatibilized with SEBS offer significant technological potential, indicating that SBRr can be introduced into the productive chain and contribute to sustainability.