EV Systems for NR. II. Further Development of Curing Systems and Vulcanizate Properties

Abstract

Abstract It was shown in Part I that the use of EV systems in NR provides a simple network in which the crosslinks are mainly monosulfidic. Part II describes in some detail the properties of vulcanizates obtained by the use of EV systems and their relationship to conventional and TMTD-zinc oxide cured vulcanizates. The disadvantages of short scorch time and heavy bloom which accompany the TMTD-zinc oxide system are overcome by the new EV systems. The monosulfidic network obtained by the use of EV systems confers on NR good overall physical properties together with much improved resistance towards thermal and thermal oxidative aging. The thermal stability of this type of network is reflected in the outstanding resistance of the vulcanizates to set and reversion, and their good resistance to heat build-up under dynamic conditions. Vulcanizates derived from EV systems have increased resistance to thermal oxidative aging due to the inherent thermal stability of the networks and good response to antioxidant protection. This increased resistance results in much better retention of tensile properties, tear resistance and fatigue cracking resistance on aging, relative to that of conventionally cured vulcanizates.