Formation of Hard Paint Films by Electron Beam-curing Method and Pigment Effect on Their Physical Properties

Abstract

Resin formulations for electron beam(EB)-cured hard paint films and pigment effect on the properties of the cured films have been studied. Formulations with an acrylate oligomer as the main constituent resulted in low hardness, 2H. In formulations consisting mainly of acrylate monomers, the content of the oligomer was fixed at 30 wt%, and the unsaturate equivalent (E_u) of the monomer mixtures was varied. A multifunctional monomer with the E_u, value of around 100 resulted in a hard (7-8H) paint film. Study for pigment effect has been carried out on a film consisting of 70% pentaerythritol triacrylate and 30% oligomer. Pigmentation by TiO₂ resulted in modulus reinforcement. However, the dynamic storage moduli of the paint film containing TiO₂ with different surface treatments showed no significant difference, whereas degree of reinforcement for thermosetting polymers was reported to be greater when the pigment-polymer adhesion was stronger. The adhesive strength of the paint film attained a maximum at a definite pigment volume concentration.