Investigation on the structure-property relationships for films obtained from UV curable coatings

A number of poly(ethyleneglycol)- and poly(propyleneglycol)- , ω-diacrylates, with different MW in the range 200–2000, were subjected to UV curing as thin films and the properties of the obtained crosslinked polymers were investigated. The total double bond conversion was determined by Fourier transform infrared spectroscopy (FTIR). Direct scanning calorimetry (DSC), thermal mechanical analysis (TMA) and dynamic-mechanical thermal analysis (DMTA) were used to evaluate the thermal and dynamic-mechanical behaviour of the networks obtained. The double bond conversion was found to be always complete, with the exception of the lowest MW oligomers. T_g values were found to decrease with increasing the MW of the oligomers used for both series. The equilibrium swelling in water was found to increase with increasing MW that is with decreasing the crosslinking density of the network. Mixtures of different oligomers with a typical epoxyacrylate resin were also examined. A sharp increase of the total double bond conversion in the presence of the oligomers was observed. The T_g values of the obtained films were found to decrease with increasing oligomer MW in agreement with the data obtained by using the pure acrylate oligomers. The results obtained are discussed in terms of the crosslinking density of the networks formed in the curing process.