Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and wheat straw fibre composites: thermal, mechanical properties and biodegradation behaviour

The thermal and mechanical behaviour of a biotechnological polyester (poly( 3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) reinforced with wheat straw fi bres has been investigated. In order to improve chemico-physical interactio ns between the components, the reinforcing agent has been previously submit ted to a treatment with high temperature steam leading to fibres richer in cellulose and more reactive. The addition of straw fibres has been found to increase the rate of PHBV crystallisation, while it does not affect the cr ystallinity content. Furthermore, the comparison of the mechanical properti es has shown that the composites exhibit higher Young moduli and lower valu es of both the stress (sigma(B)) and strain (epsilon(B)) to break than the neat matrix of PHBV. The biodegradability in different environments by mean s of short and long term tests has been studied. It has been observed that the presence of straw does not affect biodegradation rate evaluated in liqu id environment and in long term soil burial tests. In the composting simula tion test the rate of biodegradation is reduced for composites with more th an 10% of straw content. The morphology of the composites has also been inv estigated and correlated to the biodegradation process. (C) 2000 Kluwer Aca demic Publishers.