EFFECT OF VULCANIZING SYSTEMS ON TEMPERATURE PROPERTIES OF RUBBER BASED ON ETHYLENE PROPYLENE RUBBER

Abstract

The properties of rubbers based on ethylene propylene rubber (EPM) KELTAN 3050, vulcanized by a combination of various vulcanization accelerators, were studied. There were four types of vulcanizing systems (VS): organic peroxide (I), a mixture of organic peroxide and sulfur (II), a mixture of organic peroxide, sulfur and sulfenamide accelerator (III), a mixture of peroxide, sulfur, sulfenamide and thiuram accelerators (IV). Mechanical properties of vulcanizates at room temperature (MP), compression set at 100 °C for 24 hours and 20 % deformation (CS), cold resistance coefficient for elastic recovery after compression at –60 °C (Kv) and brittleness temperature (BT) according to the corresponding GOST, as well as vulcanization kinetics and torque (M) for rubber compounds on the MDR3000, MonTech device were determined. For all vulcanizates, the crosslink density (CLD) was calculated using the Flory-Rehner equation by the method of equilibrium swelling in toluene. The MP for all VS were significantly higher or at the level of VS I, the BT for all VS were at a level below minus 70 °C, The Kv increased in the series I < II < III < IV from 0,11 to 0,21, but the CS also increased. The CLD in this series decreases, which correlates with the data for the maximum value of M. The clear correlation between Kv and CLD is not established. The influence of the vulcanization mechanism and the structure of cross-links on the studied rubber properties are considered. It is shown that to obtain the maximum temperature range of rubber use, combined peroxide-sulfur VS of an optimal ratio of peroxide and sulfur agents are preferred.