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

This paper reports the results of spectroscopic investigations carried out on film cast from a system consisting of cycloaliphatic diepoxide, epoxidiz ed natural rubber (ENR-50), and glycidyl methacrylate (GMA) and cured by th e UV radiation. GMA acts as a reactive diluent for the ENR. Triphenyl sulph onium hexafluoro antimonate was used as the cationic photoinitiator. Result s reported in a previous paper showed that ENR acts as a toughening agent. Optical microscopic studies were suggestive of the existence of two-phase m orphology 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 favorabl e interactions occurred between the different components of the coating sys tems employed in our studies to promote effective adhesion between the elas tomeric domain and the resin matrix. Systematic spectral studies were, ther efore, conducted with a view to understanding how different components of t he hybrid coating system interact. The results showed that the acrylic doub le 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 crosslinki ng reactions ultimately producing an interpenetrating polymer network, a re sult conducive to effective toughening of the epoxy resins, which are intri nsically brittle. (C) 19991999 John Wiley & Sons, Inc.