Role of additives on UV-curable coatings on wood

Abstract

An epoxy resin-coating formulation was prepared from diacrylated epoxy bisphenol-A-epichlorohydrin and a reactive monomer, tripropyleneglycol diacrylate. The additives, silane and fluorochemicals, were included in the formulation to evaluate their effects on the UV curing of the epoxy resin onto timber. Thin films coated on wood substrates were cured under UV radiation in the presence of the photoinitiator, benzoin ethyl ether. Adhesion of the cured films onto wood substrates was evaluated using the cross-cut and the pull-off tests. Film hardness was evaluated using the pencil hardness and the pendulum hardness tests. Water repellency of the films were measured from contact angles using a telegoniometer. Scanning electron microscopy (SEM) was used to investigate the interface between the films and the wood substrates. These studies showed that silane only enhanced the adhesion of the film onto the wood substrates but had no effect on the hardness of the films. The additives improved the water repellency of the films with the fluorochemicals, exhibiting dramatic improvement. SEM revealed that only the fluorochemical aided the penetration of the resin into the wood. © 1996 John Wiley & Sons, Inc.