Thermosetting composition and process for preparing fiber-reinforced composites

Abstract

A two-component curable epoxy resin system is disclosed. The resin system includes an epoxy resin component containing at least 80% by weight of a polyglycidyl ether of a polyphenol that has an epoxy equivalent weight of up to about 200 and contains no more than 2% by weight of monohydrolyzed resin species. The system also includes a hardener mixture that has an amino hydrogen equivalent weight of from 35 to 90 and contains at least 90% by weight of a mixture of (i) from 5 to 75% of the combined weight of (i), (ii) and (iii) of one or more compounds that have at least two primary and/or secondary aliphatic amino groups and which have no phenolic groups; (ii) from 10 to 95% of the combined weight of (i), (ii) and (iii) of one or more aminophenol compounds that contain one or more primary and/or secondary aliphatic amino groups and at least one phenolic group and (iii) from 0 to 50% of the combined weight of (i), (ii) and (iii) of one or more phenolic compounds that contain two or more phenolic groups and do not contain primary or secondary amino groups. The epoxy resin component and hardener mixture are present in amounts sufficient to provide from 1.05 to 1.35 equivalents of aliphatic amine hydrogens per equivalent of epoxide groups provided by the epoxy resin component. The system has beneficial curing characteristics that make it useful for producing fiber-reinforced composites in a resin transfer molding process.