Curing and rheological study of epoxy molding compound with novel phosphonium silicate latent accelerators

Abstract

AbstractLatent curing accelerators are significant for curing and molding controlling of epoxy molding compounds. Two novel phosphonium silicate latent accelerators, tetraphenylphosphonium bis(2,3‐dioxy‐naphthalene)methylsilicate (P‐Si‐Me) and tetraphenylphosphonium bis(2,3‐dioxy‐naphthalene)phenylsilicate (P‐Si‐Ph) were synthesized and characterized. The catalytic performance of P‐Si‐Me and P‐Si‐Ph on epoxy/phenolic resin system was evaluated and compared with commercial organophosphine accelerators triphenyl phosphine (TPP) and triphenylphosphine‐1,4‐benzoquinone (TPP‐BQ). Systems with four accelerators displayed similar autocatalytic curing reaction mechanism, and the curing and rheological behavior of four epoxy systems could be well described with the diffusion factor‐incorporated Kamal model, and Castro and Macosko model, respectively. DSC and rheology results showed that the latency of four accelerators followed the order of P‐Si‐Ph ≈ TPP‐BQ >> P‐Si‐Me > TPP, while the catalytic reactivity followed TPP > P‐Si‐Me > P‐Si‐Ph > TPP‐BQ. DMA results exhibited that epoxy systems with phosphonium silicate accelerators had higher Tg than that with TPP and TPP‐BQ. The latency and catalytic performance of phosphonium silicate accelerators were attributed to their ionic complex nature. Moreover, the substituent on silicate anion had obvious impact on the performance of accelerators.