Electrochemical effects during thermoset moulding

Abstract

This paper describes an investigation of the substantial electrochemical potentials which have been found to arise if dissimilar metals are immersed in an electrolyte of polyester resin while it is curing. Sharp initial changes in the e.m.f. indicate the moment of arrival of resin at the electrodes, and the subsequent magnitude can be used to indicate the state of cure. The e.m.f. was found to be influenced by the addition of calcium carbonate filler powder to the base resin, as well as by the choice of electrode metals. Aluminium and copper were selected for practical applications, and tested under transfer moulding conditions. A prototype instrument suitable for incorporating in a mould to indicate the completion of filling and the state of cure in a resin transfer moulding process is described. The results will also have application to other thermoset moulding processes.