Rheology and thermal transition state of polyvinyl alcohol-cassava starch blends

This communication focuses to unveil the molten behaviour of biodegradable polyvinyl alcohol (PVOH) blending with native cassava starch (CSS). Different percentages of CSS were blended with glycerol plasticized PVOH (PPV) to study the shear rate-viscosity at 190 degrees C and the thermal transition state at 200 bar (20.265 MPa). The outcomes showed that the viscosities of PPV-CSS compounds reduced as the PPV composition increased. This indicates that the addition of PPV helps to improve the processability of thermoplastic starch compound. On the other hand, a higher percentage of CSS would disrupt the transition of specific volumes at the molten stage (160-180 degrees C) of PPV-CSS compounds. The transition was lowered due to the loss of crystallinity in PPV. It is postulated that injection moulding of PPV-CSS blends has lower volume shrinkage than PPV due to lower thermal transition and crystallinity of the compounds. (C) 2010 Elsevier Ltd. All rights reserved