UV curing of surface coating system consisting of cycloaliphatic diepoxide-ENR-glycidyl methacrylate by cationic photoinitiators?characterization of the cured film by FTIR spectroscopy

Abstract

This paper reports the results of spectroscopic investigations carried out on film cast from a system consisting of cycloaliphatic diepoxide, epoxidized natural rubber (ENR-50), and glycidyl methacrylate (GMA) and cured by the UV radiation. GMA acts as a reactive diluent for the ENR. Triphenyl sulphonium hexafluoro antimonate was used as the cationic photoinitiator. Results reported in a previous paper showed that ENR acts as a toughening agent. Optical microscopic studies were suggestive of the existence of two-phase morphology consisting of an elastomeric domain and the resin matrix domain. For effective toughening, it is essential that good adhesion exists between these two domains. It was of interest, therefore, to know whether favorable interactions occurred between the different components of the coating systems employed in our studies to promote effective adhesion between the elastomeric domain and the resin matrix. Systematic spectral studies were, therefore, conducted with a view to understanding how different components of the hybrid coating system interact. The results showed that the acrylic double bonds, as well as the epoxy groups of GMA, the isoprene double bonds and epoxy groups of ENR, and the epoxy groups of cycloaliphatic epoxide resin all participate in a scheme of photoinitiated polymerization and crosslinking reactions ultimately producing an interpenetrating polymer network, a result conducive to effective toughening of the epoxy resins, which are intrinsically brittle. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1569–1577, 1999