Simultaneous improvement of mechanical properties and curing temperature of cyanate ester resin by in situ generated modifier polymer having phenolic OH group

Reduction in curing temperature of cyanate ester resin and improvement in mechanical properties of the corresponding cured resin were simultaneously achieved by in situ generation of N-(4-hydroxyphenyl)maleimidestyrene copolymer (HPMS) during the resin curing process. The results of differential scanning calorimetry and FT-IR spectroscopy measurements indicated that N-hydroxyphenylimide unit in HPMS reduced final curing temperature of bisphenol A dicyanate (BADCY) to 200 degrees C. It was also revealed that fracture toughness (K-IC), flexural strength and flexural modulus of the cured resin modified with in situ generated HPMS were increased by 26%, 9.2% and 4.5%, respectively, compared to those of the unmodified cured resin. The morphology of the modified cured resin observed by transmission electron microscope showed that HPMS was finely dispersed in the cyanate ester resin matrix on the order of 200-1600 nm. This high compatibility between the resin matrix and modifier polymer are derived from both the in situ generation of the modifier polymer and the formation of covalent bond at the matrix-modifier interface, which resulted in the improvement of toughness, strength and modulus of the cured resin.