Unsaturated modified poly(vinyl alcohol) and ethylene-vinyl alcohol copolymers. Crosslinking through double bonds

Poly(vinyl alcohol) (PVA) and two ethylene-vinyl alcohol copolymers were esterified with undecenoyl chloride and a mixture of undecenoyl and benzoyl chlorides to test how the double bond content and aromatic or aliphatic spacers can affect the further crosslinking reaction. In all cases crosslinking was only possible by using a peroxide initiator to prevent simultaneous thermal degradation. Isoconversional kinetic analysis was applied to dynamic DSC data. This study reveals the complexity of the crosslinking process because the activation energy depends on the conversion degree. In the polymers which contain most double bonds, diffusion is the rate limiting step at high conversion. As a general trend, E_a values increase when the number of double bonds decreases. However, when there are many benzoate moieties, E_a values are lower probably due to the more expanded conformation that the random coil must adopted.