High-Temperature Adhesives Based on Alder-ene Reaction of Diallyl Bisphenol A Novolac and Bismaleimide: Effect of BMI Structure and Novolac Molar Mass

摘要

Diallyl bisphenol A formaldehyde novolac (ABPF) resin was cured with four structurally different bismaleimides (BMIs) at high temperature through an Alder-ene reaction which resulted in thermally stable network polymers. The adhesive characteristics of the different BMI-ABPF systems were evaluated in terms of the lap shear strength (LSS) on aluminium substrates at varying temperatures up to 250 deg C. The LSS properties were not significantly affected by the structure of the BMI. Although the LSS of BMI-ABPF systems perse were not particularly high due to the brittle nature of the cross-linked structures, all the systems exhibited remarkably good retention of LSS at high temperatures. Replacing ABPF with its monomeric analogue i.e. o,o'-diallyl bisphenol A (DABA) resulted in better adhesion, but in a poorer thermo-adhesive profile. Comparison of DMA and thermo-adheisve profiles implied that in the majority of the cases molecular relaxations at higher temperature are conductive to matrix toughening which results in enhanced adhesion properties.