Copolyureas formed by reaction injection moulding: correlations between chemical structure, thermal properties and microphase separation

Abstract

Segmented copolyureas comprising soft segments based on a polyoxypropylene polyamine and hard segments based on 4,4′-diphenylmethane diisocyanate (MDI) reacting with either 3,5-diethyltoluenediamine (DETDA) or methylene-bis-2,6-diisopropylaniline (MDIPA) have been formed by reaction injection moulding (RIM). Novel RIM materials with MDI/DETDA hard segments and poly(dimethylsiloxane) soft segments have also been studied. RIM materials were characterized by d.s.c. and d.m.t.a. to obtain soft- and hard-segment glass transition temperatures, T s g and T H g, and the degree of microphase separation. Correlations between the chemical structure, thermal properties and microphase separation have been established using interaction parameters, χ, estimated from solubility parameters, and critical values of χ estimated from block copolymer theory. Hard-segment sequence length increases with hard-segment content, and values of T H g are shown to increase according to the Flory-Fox relation. The effects of process and thermal histories on microphase separation are interpreted with reference to a phase diagram.