The effect of treatment with HEMA and gamma irradiation on the starch:PVA films studied by differential scanning calorimetry and thermogravimetry

Abstract

Basic studies were conducted dealing with the influence of treatment with hydroxyethyl methacrylate (HEMA) supported by gamma irradiation on physicochemical properties of the starch:PVA films (45:55, glycerol content of 30 wt%). The films were placed in a 10% monomer solution, irradiated with 60Co gamma rays applying a dose of 25 kGy, then heated at 45 °C for 2.5 h and subjected to a prolonged contact with the solution. Simultaneously, the reference sample subjected to the same treatment without action of HEMA, and additionally the samples irradiated in monomer solution without heating step, were prepared. FTIR spectroscopy has shown an effective grafting of HEMA. The differences were found between the course of thermal degradation occurring in HEMA treated sample and the reference sample both in nitrogen and in air. Data analysis indicated formation of the fractions characterized by an increased as well as by a decreased thermal stability. Simultaneously, DSC enabled to discover the differences between melting, crystallization, glass transition and structural relaxation phenomena taking place in the monomer treated and the non-treated samples. The changes were referred to a decrease in the crystallinity accompanied by an increase in the ordering in the amorphous phase. TGA and DSC data were related to chemical changes shown by FTIR spectroscopy and by gel content data and discussed in terms of degradation as well as grafting of HEMA onto the polymer matrix. The increased temperature of the treatment raised degree of the occurring changes.