Progress in improving high-temperature properties of thermosetting resins: development of the microheterogeneous model for the formation of crosslinked rolivsan-epoxy blends

Abstract

Thermochemical transformations in blends of rolivsans (ROLs, i.e., compositions of (di)vinylaromatic ethers and thermosensitive (di)methacrylates) with epoxy resins were used to obtain new glassy heat resistant highly crosslinked ROLs/epoxy blends (block copolymers) which differ in composition, crosslink density, chemical, topological and morphological structure. The influence of the ROLs/epoxy blocks ratio in the blends and temperature-time regimes of curing on heat resistant properties of the materials was estimated by studying temperature dependences of breaking strength at three-point flexural test, dynamical elastic modulus, mechanical loss tangents (in dynamic mechanical analysis, DMA) and thermooxidative aging processes. Unusually high values of high temperature strength of the epoxy-modified ROLs were reached when using a new method for enhancing heat resistance and thermal stability of microheterogeneous network polymers (cured resins) consisting of highly crosslinked microdomains. These microdomains are weakly bound to each other by defective polymer interlayers. This method is illustrated by the example of transformations in ROLs/epoxy blends; it suggests (macro)molecular design and curing development. The method involves functionalization of microdomains, target delivery of epoxies into interlayers and carrying out high temperature chemical reactions in these interlayers. These reactions lead to additional crosslinking of supramolecular formations (highly crosslinked ROL microdomains) by epoxy bridges. The results obtained in the studies of structural transformations in rolivsans modified with epoxy resins were used as a basis for the new approach to enhancing heat resistance and thermal stability of thermosetting resins.