An efficient vulcanization system with pyrrolidinylthiourea in natural rubber

Binary accelerator formulations involve the use of two different accelerators in the rubber vulcanization system, often leading to improved vulcanizate properties. Binary accelerator based formulations have emerged as popular vulcanization systems to minimize pre-vulcanization, permit the vulcanization at low temperature in a shorter time and produce a vulcanizate with superior mechanical properties. Thiourea and its derivatives can play an important role in binary accelerator systems. In the present study, a new derivative of thiourea namely N-benzoyl-N’, N’-pyrrolidinylthiourea (BPTU) has been synthesized, characterized and incorporated as binary accelerator along with 2-mercaptobenzothiazole (MBT) for the vulcanization of natural rubber in the gum and filler systems. Appreciable reductions of cure time and addicate improvement in mechanical properties are the main outcomes of the study when compared to the reference mixes containing MBT or BPTU alone as accelerator. The variation in mechanical properties has been correlated to the crosslink formation in various vulcanisates used in the study. Thermogravimetric studies of the new system were also investigated. BPTU alone can also act as an accelerator but it is more efficient in a binary system.