Testing of polyvinyl alcohol and starch mixtures as biodegradable polymeric materials

The mechanical properties, thermal. behaviour and biodegradation of some po lymeric materials based on polyvinyl alcohol and starch, in the presence of urea (used as a micro-organism nitrogen source/plasticizer) and glycerine (used as a plasticizer) have been studied. The chemical composition optimiz ation of the analysed blends was carried out using a second order factorial experimental design. The progress of biodegradation was evidenced by means of scanning electronic microscopy, differential scanning calorimetry and t hermogravimetric measurements. The evaluation of the weight loss of the sam ples at the end of the biodegradation process was also carried out. The wei ght loss after 18 days of inoculation with microorganisms is between 38 and 73% by weight and is influenced by the composition of the blend as well as by the nature of the microorganism used, During biodegradation, plasticise rs (glycerine and urea) and starch are consumed together with some amorphou s structures from polyvinyl alcohol. The crystalline structures of polyviny l alcohol which remained after biodegradation show high values of entalpy, and contribute to an increase in the apparent thermal stability of the biod egraded samples. (C) 2000 Elsevier Science Ltd. All rights reserved.