ConclusionsUnfilled NR was cured with two differentsulphur vulcanisation systems, conven-tional and efficient, and their physical prop-erties compared.The conventional cure system has shownreversion at all contents, whereas the tor-que for the efficient cure system hasreached a plateau level. In the latter, athigh accelerator/sulphur ratios (above7.2/0.6 parts) a decay in S 0takes place aftersome time. The torque varies linearly withthe crosslink density for the conventionalcure system, whereas for the efficientcure system the relationship departs fromthe linearly increasing torque values whichare characteristic for the conventional cure