Electron pretreatment of sheet molding compounds (SMC)

Based on thermal investigations on Class-A SMC test panels that were molded at different conditions incomplete curing reaction of un-saturated resin and reactive thinner as well as the post-curing and out gassing during industrial coating processes are the two main reasons for the observed coating problems. Furthermore, it was found that surface properties of test panels, especially contact angles and surface roughness, strongly depend on processing parameters of curing and coating as well as cleaning and pickling methods. The same was found with industrially processed SMC Class-A automotive parts. It is a great challenge to overcome these disadvantages by a cost efficient robust new procedure which fulfils the requirements of industrial coating processes. Based on electron beam curing and functionalization via high energy electrons a novel pre-treatment procedure was developed. By one additional step, post-curing of the SMC-parts and surface functionalization, is achieved. This novel pre-coating technology increases the efficiency of inline coating processes; a patent application has been submitted.