Optimising natural rubber recycling capability using combinations of copper(ii) ion and phosphine inhibitors

Previous work demonstrated that controlled inhibition of disulphide metathesis using copper(ii) methacrylate (CuMA) can enable high recycling efficiency in conventional (CV) and semi-efficient (SEV) cure systems. However, CuMA's high cost and limited commercial availability restrict its industrial application. This study investigates triphenylphosphine (TPP) as a more accessible inhibitor, used alone or in combination with CuMA, to achieve comparable recycling performance at reduced cost. Cure characteristics were evaluated using Moving Die Rheometer analysis, and mechanical properties were assessed through tensile testing to quantify recycling efficiency. Results show that TPP alone provides moderate recyclability, while TPP-CuMA blends deliver efficiencies similar to pure CuMA in CV systems and superior performance in SEV systems. These findings highlight a commercially viable approach to recycling sulphur-cured NR compounds, reducing reliance on virgin rubber and supporting sustainable manufacturing.