Studies on the effect of Acrylic acid & Methyl-meth-acrylate monomers on the Viscoelastic behavior of Divinylester resin of Bisphenol-A UV cured sheets

Abstract

Tg is important both as a measure of the degree of cure and for prediction of viscoelastic behavior of cured sheets DMA is an extremely versatile thermal analysis method that provides as much information about the physical properties of a sample in a single test. At the glass transition, the storage modulus decreases dramatically and the loss modulus reaches a maximum. In the present work, Vinyl ester resin based UV cured sheets were casted and analyzed for glass transition temperature with the help of DMTA. The thermal stability of the casted sheets was studied with derivative weight loss curves obtained through simultaneous TGA/DTA thermograms. The glass transition temperatures of the casted UV Cured sheets were found between 61-77 0 C corresponding to maximum tan delta values. On the basis of the findings presented in this article, it can be concluded that the glass transition temperature is decreasing on increasing the acrylic acid and methyl methacrylate concentration in UV curable formulations, which is indicating a decrease in degree of crosslinking but on the other hand mechanical properties have shown a remarkable increase. The specific gravity of the sheets was found in the range 1.46-1.21. However, after crosslinking with acrylate monomers, thermal stability of these UV cured sheets is increasing and hence the sheets could withstand relatively high temperatures without significantly affecting other properties. The average molecular weight between the cross links (Mc) of the cured formulations was also calculated from equilibrium shear modulus at thermodynamic temperature of 25 0 C and compared with theoretical values.