Non-isothermal crosslinking of ethylene vinyl acetate initiated by crosslinking agents: kinetic modelling

Abstract

The non-isothermal crosslinking process of ethylene vinyl acetate (EVA) initiated by several crosslinking agents was studied by using differential scanning calorimetry (DSC). The crosslinking agent tert-butylperoxy 2-ethylhexyl carbonate (TBEC) exhibited much shorter reaction time and lower reaction temperature. The effect of the crosslinking agent TBEC on the EVA crosslinking process was further analyzed by using Avrami, Ozawa, Mo and Flynn-Wall-Ozawa (FWO) methods, respectively. The small fluctuations in the values of Avrami exponent n and Mo parameter a indicate that the EVA crosslinking mechanism is basically unchanged with increasing heating rate and crosslinking agent content. The change of the Ozawa exponent m is presumably due to the increase in viscosity of EVA/TBEC samples during the crosslinking process. The heating/cooling function F(T) values and the activation energy E_a are dependent on the conversion rate α. In addition, E_a shows irregular changes in the early stages of crosslinking, and increases with the increase of conversion rate α in the later stages of crosslinking.