Vulcanization kinetics and mechanical properties of filled ethylene-vinyl acetate copolymer rubber composites

Abstract

Abstract The vulcanization reaction of ethylene vinyl acetate copolymer (EVM) rubber is fast, resulting in poor processing safety. EVM is often filled with flame-retardant fillers as insulating or sheathing material for wires and cables. Herein, the effects of flame-retardant magnesium hydroxide (Mg(OH)2), aluminum hydroxide (Al(OH)3) and of the traditional reinforcing fillers carbon black (CB) and silicon dioxide (SiO2) on the vulcanization kinetics of EVM were investigated. The vulcanization characteristics showed that the scorch time (T 10) of the unfilled EVM (KB), SiO2/EVM, Mg(OH)2/EVM, and Al(OH)3/EVM composites was about 1.75 min. T 10 of the CB/EVM composite was 2.22 min. Compared with KB, the activation energy (E a ) increased by about 15 kJ/mol for CB/EVM composites and by about 5 kJ/mol for SiO2/EVM, Mg(OH)2/EVM and Al(OH)3/EVM composites. The results indicate that CB delays the vulcanization time of EVM rubber, slows down the rate of vulcanization reaction and improves the safety of vulcanization. The addition of SiO2, Mg(OH)2 and Al(OH)3 has little effect on the vulcanization reaction. The mechanical properties show that CB/EVM is more uniformly vulcanized and has the best mechanical properties with a tensile strength of 17.61 MPa and elongation at break of 404.58 %. Mg(OH)2/EVM and Al(OH)3/EVM samples have prominent vulcanization non-uniformity resulting in poor mechanical properties.