Structure development and properties of plasticized pva-starch-paddy straw composites

Paddy straw is often burnt in the fields or disposed of in ways that cause extensive environmental pollution. The present study focused on using paddy straw in bio-compostable composites fabricated with polyvinyl alcohol (PVA) and thermoplastic starch blends as a matrix. Locally available paddy straw was chopped, cleaned and treated with 15% NaOH solution for four hours. The alkali treatment produced changes in the crystal structure and surface morphology of the paddy straw. Then, it was dispersed in blends of PVA and starch solutions containing polyethylene glycol (PEG200) as plasticizer. The PEG200 acted as both plasticizer and compatibilizer, as evidenced by the single glass transition peak and the lower melting point of the film cast from these blends. These composite films had higher thermal stability, increased tensile strength, but also flexibility. These properties were associated with structure development with strong hydrogen bonding interaction between the paddy straw and PVA-starch blends, which was supported by results of characterization studies.