BLOCKED DIISOCYANATE POLYESTER-TOUGHENED NOVOLAK-TYPE PHENOLIC RESIN - SYNTHESIS, CHARACTERIZATION, AND PROPERTIES OF COMPOSITES

A blocked diisocyanate polyester was synthesized to copolymerize with novolak-type phenolic resin. From the results of TR and NMR spectra, i t was found that the blocked diisocyanate polyester reacts with the hy droxyl group of the novolak-type phenolic resin at high temperature.Th e deblocking temperature for the novolak-type phenolic resin is 120 de grees C. The blocking agent, epsilon-caprolactam, is convenient for th is system. The copolymer exhibited a single glass transition temperatu re and a negative deviation of the glass transition temperature. The r esults showed that the copolymer system is miscible and the molecular motion of the copolymer is increased with the addition of a modifier. The interface between the modified phenolic resin and the glass fiber is improved and the tensile strength of pultruded composite is increas ed with the modifier content. (C) 1998 John Wiley & Sons, Inc. S Appl Polym Sci 69: 1119-1127, 1998.