Pultruded fiber‐reinforced polyurethane‐toughened phenolic resin, I. Reactivity and morphology

A phenolic resin/polyurethane copolymer was synthesized by reaction of a phenolic resin, a blocked‐polyurethane and p‐toluene sulfonic acid. The copolymer provides a good balance between the processability (including pot life, reactivity) and toughness. The reactions that proceeded during the synthesis of the copolymer was investigated by IR spectroscopy. It was found that blocked polyurethane reacted with the hydroxy group of the phenolic resin. Glass fiber‐reinforced composites showed excellent bonding between fiber and matrix as revealed by SEM photographs. An overlap peak was found from the DMA diagram; it indicated that an interaction existed between phenolic resin and polyurethane and that improved the toughness of the phenolic resin.