Properties of thermoplastic blends: starch-polycaprolactone

Different compositions of wheat thermoplastic starch (TPS) and polycaprolactone (PCL) are melt blended by extrusion and injected. Different properties are determined: mechanical properties (tensile and impact tests), thermal and thermomechanical properties (DSC and DMTA) and hydrophobicity (contact angle measurement). A large range of blends is analysed with different glycerol (plasticizer):starch contents ratios (0.14:0.54) and various PCL concentrations (up to 40 wt.%). From the behaviour of each polymeric system, it is possible to analyse the relationship properties of each component proportion on the blends. The ageing of the system is studied and shows a structural evolution of the material after injection during several weeks. We have noticed a fairly low compatibility between both polymeric systems. Finally, the addition of PCL to TPS matrix allows to overcome the weakness of pure TPS: low resilience, high moisture sensitivity and high shrinkage, even at low PCL concentration, e.g. 10 wt.%. (C) 2000 Elsevier Science Ltd. All rights reserved.