Controllable Modification of Rubber Achieved through Biobased Inverse Vulcanized Compounds

The biobased inverse vulcanized compound named poly(sulfur-itaconic acid) (SIA) was synthesized by reacting itaconic acid containing double bonds with sulfur to control rubber modification precisely. SIA was incorporated into the rubber network as a vulcanizing additive to promote vulcanization alongside an activator. Utilization of sulfur and SIA could regulate the cross-link density of the vulcanized rubber and improve its mechanical properties, with a 10% increase in tensile strength (up to 28.17 MPa) and a 14% rise in elongation at break (up to 646%), while also promoting filler dispersion. The polysulfides in SIA exhibited the ability to undergo thermal decomposition and reorganization at 150 °C, thereby enabling desirable recyclability for rubber materials. After over three recycling cycles, sample tensile strength remained consistently stable at 8 MPa, while elongation at break maintained a steady value of 400%. Further, introducing SIA as a processing aid into the carbon black-filled natural rubber composite system can achieve a better aging resistance performance than the original system. SIA endows rubber composites with excellent mechanical properties, improved interfacial interactions, recyclability, and aging resistance. It has the potential to become a biobased multifunctional additive.