AbstractSolution polymerization of epoxytetrahydrophthalic anhydride (ETHPA) has been thoroughly studied by using numerous solvents and catalysts. Products have been obtained in high yields, particularly when triethanolamine was the catalyst. This suggests that this catalyst should be considered for further applications utilizing ETHPA. However, the solution polymerization method cannot be used alone to define the effects of various catalysts on standard nonsolvated resin systems, because polymerization is greatly affected not only by the addition of solvent but also by the type of solvent. In addition, the action of the catalyst seems to depend greatly upon what solvent is employed. The reason for this dependence has not been established. The effects of the addition and reaction of ETHPA with commercial epoxy resin formulations have been investigated by means of heat distortion tests and differential thermal analyses. In most cases, although a moderate improvement was found in the thermal properties of the resins, occasional excellent results were obtained. A 10°C. increase in HDT is observed with a 2 wt.‐ addition of ETHPA for bisphenol A epoxy resin–bicyclic anhydride mixture. The degree of elevation ofTgand HDT with the addition of ETHPA obviously depends not only on the composition of the resin system but also on its cure temperature. A good correlation occurs between heat‐distortion temperatures and glass transition temperatures. Some few anomalous data, however, are found which point to the fact that further investigation is required before HDT andTgcan be interchanged without prior evidence of a definite relati
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