Allyl ether of aralkyl phenolic resin with low melt viscosity and its Alder-ene blends with bismaleimide: synthesis, curing, and laminate properties

This paper outlines the synthesis and characterization of O-allyl aralkyl phenolic (O-allyl Xylok, OAX) resins having low melt viscosity and its Alder-ene blends with 2, 2′-bis 4-[(4′-maleimido phenoxy) phenyl] propane. The blends manifested a three-stage curing pattern that converged to a two-stage pattern on enhancing the maleimide content. The polymerization kinetics of typical allyl and maleimide rich resin systems showed apparent activation energy increasing and pre-exponential factor decreasing from ene to the Diels–Alder step. Increased allyl content improved mechanical and impact properties of the composites at ambient temperature, although it diminished the retention of interlaminar shear strength at elevated temperature. Increased maleimide content of the resin was conducive for the higher rigidity for the composite and its retention at elevated temperature. A substantial increase in Tg (from 153°C to 280°C) and thermal stability was observed with an increase in maleimide content. High allyl content resulted in improved mechanical properties thanks to better resin–reinforcement interaction as revealed from morphological analysis.