Synthesis and evaluation of liquid epoxy resin derived from pyrogallol

Abstract

The epoxy resin derived from pyrogallol (1,2,3-trihydroxybenzene) was synthesized and investigated for its physical properties. Pyrogallol tends to have byproducts with cyclic structures due to three adjacent phenolic hydroxyl groups, which differs from conventional epoxidation process. For suppressing these byproducts, an epoxy resin (PyTGE) exhibiting a liquid form was obtained industrially, by separating the addition reaction and the ring closure reaction. Cured materials of PyTGE and 4,4’-diaminodiphenylsulfone showed both high modulus and high strength. In the PyTGE cured product, the free volume corresponding to the void part was small, and it is assumed that a denser (condensed) network structure was formed by the adjacent epoxy units. In addition, in verification using model compounds, the catechol-type epoxy might form a 11-membered cyclic structure consisting of an amino group, and the cyclic molecules affected the properties of the cured products.