RIGID-ROD NETWORKS - LIQUID-CRYSTALLINE EPOXY-RESINS

Liquid crystalline polymers are well known for their unique mechanical and theological properties. In recent years, some interest has been d evoted to the study of a new class of liquid crystalline thermoset bas ed on epoxy resins. Liquid crystalline epoxy resins can be obtained ei ther by curing glycidyl terminated prepolymers over a range of tempera ture in which the mesophase is stable, or by reacting epoxy functional ized rigid monomers with a suitable curing agent. In our work this sec ond approach has been followed. An unusual behaviour has been found fo r the form of the exotherm during increased curing temperature. Fractu re toughness K-q, was found to decrease with increased curing temperat ure. This experimental evidence has been correlated with the reduction of the extent of liquid crystalline character with temperature.