Evaluation of different formulations of SBR/NR elastomeric compounds in order to minimize pre-vulcanization

This work aimed to develop and evaluate new formulations for the rubber vulcanization system based on styrene-butadiene rubber (SBR) and natural rubber (NR), aiming at reducing the formation of pre-vulcanized compounds by increasing storage time before processing. Alternative formulations have been developed in relation to a standard formulation employed by a company of the sector, varying the components of the vulcanization system (activators, agents and accelerators). The formulations were evaluated by rheology tests, tensile strength and elongation at break, hardness, permanent compression deformation (DPC), accelerated aging in greenhouse and absolute density. There were significant variations in the properties of the compounds with the modifications made in the vulcanization systems (S1, S2, S3, P1 and P2), when compared with the standard vulcanization system (S0), mainly when organic peroxides were used as agent of vulcanization. Of all the formulations evaluated, the one that used sulfur donor and a higher accelerator / sulfur ratio, compared to the standard vulcanization system showed all properties according to the technical specification required for the standard compound (S0) with reduction in the time of storage and minimization of pre-vulcanization.