SYNTHESIS OF CHEMICALLY BONDED POLY(VINYL ALCOHOL)-STARCH COMPOSITE

Poly(vinyl alcohol) (PVA) was grafted on hydrolysed starch through int roduction of the chemically reactive bifunctional compound N-methylola crylamid (N-MAm). The grafting reaction was carried out in two separat e reaction steps. The first step was the reaction of PVA with N-MAm in alkaline medium. The reaction mechanism and reaction conditions such as alkali concentration, temperature, reaction time as well as N-MAm c oncentration were studied. According to the results obtained, the most appropriate conditions for the preparation of this reactive PVA are: treating PVA with N-MAm (1.25 mol/mol PVA) in the presence of NaOH (6% based on solution volume) at 20 degrees C for 8 h. Second step was th e reaction of this reactive PVA (N-MAm-PVA) with hydrolysed starch in the presence of NH4Cl. The latter was carried out under different cond itions including temperature, reaction time, catalyst concentration as well as N-MAm-PVA/hydrolysed starch ratio. The results obtained show that the extent of the grafting reaction is governed by each of these factors. Furthermore, GPC data showed that the molecular weight distri bution and the apparent viscosity of PVA-N-MAm-starch composite depend on the initial molecular weight of both PVA and hydrolysed starch use d.