EV Systems for NR. I. The Purpose of Efficient Vulcanization and Development of Curing System

Abstract

Abstract By means of a simple relaxed modulus test, a comparison has been made of the efficiency of sulfur utilization of various vulcanizing systems based on commercially available accelerators, or accelerator combinations, plus elemental sulfur or a sulfur donor. These initial experiments indicate three ways of increasing efficient use of sulfur for crosslinking: (1) the employment of synergistic combinations of accelerators; (2) the use of a high accelerator/sulfur ratio; (3) the substitution of elemental sulfur by a sulfur donor. Characterization of the networks formed using the EV systems developed shows that it is possible to obtain systems which are as efficient as the “sulfurless” TMTD-zinc oxide system in terms of the number of sulfur atoms combined in the network per chemical crosslink present. Independent evidence, gained by the use of chemical probes, has established that the network formed by an EV system contained only monosulfidic crosslinks and that little modification of the main chains by sulfur had occurred.