The Influence of Reactive Diluents on the Properties of UV Dual Cured Polyurethane-Modified Epoxy Monoacrylates Films

Abstract

The UV-curable liquid compositions were developed with different oligomers (epoxy diacrylates, EDA; epoxy monoacrylates, EMA; or polyurethane-modified epoxy monoacrylates, PMEMA), reactive diluents and photoinitiators. Thin films were prepared by curing these mixtures using a high pressure mercury lamp. The change of absorption peaks of double bond and epoxy group were identified by Fourier Transform Infrared (FTIR) spectra during UV dual curing process. Gel content, mechanical, volume shrinkage and thermal characterizations of the UV-cured films were investigated. The gel content, youngs modulus and stress at break turned to maximum values as the degree of polymerization achieved the maximum value, except for the strain at break. The flexibility of UV dual cured films using PMEMA as oligomer was improved due to grafting of the soft chain segments (polyurethane). The volume shrinkage test indicated that the UV dual cured films exhibited lower internal stress and higher cohesive force than simple radical UV cured films. The thermogravimetric analysis of UV cured films revealed that UV dual cured films prepared from PMEMA showed excellent thermal stability.