Preparation and characterization of highly thermostable polyisocyanurate foams modified with epoxy resin.

A series of epoxy resin--modified polyisocyanurate (EP-PIR) foams with oxazolidone (OX) rings and isocyanurate (IS) rings have been successfully prepared by the reaction of polymethylene polyphenyl isocyanate (PAPI) and diglycidyl ether of bisphenol-A (DGEBA). Fourier transform infrared spectroscopy and differential scanning calorimetry are performed to investigate the influence of curing temperature on the chemical structure of EP-PIR foams. The results indicate that low temperature is beneficial to the formation of the IS ring, and high temperature is in favor of the OX ring. The influence of the mole ratio of [PAPI]/[DGEBA] on the mechanical properties and thermal stability has also been studied. With the increase of [PAPI]/[DGEBA], the specific compressive strength shows a maximum of 0.0135±0.0003 MPa m³/kg. The optimized mole ratio of [PAPI]/[DGEBA] is around 2.5 to reach the better mechanical and thermal properties, and the glass-transition temperature is as high as 323.5ºC. [ABSTRACT FROM AUTHOR]