Characterization of water-free thermoplastic starch blends for manufacturing processes

As part of an investigation into the use of cheap water-free thermoplastic starch (TPS) as a filler in rotomoulding applications, TPS/PE (polyethylene) blends were manufactured and tested as extruded strands, injection-moulded samples and rotomoulded samples. The effects of starch type, plasticizer type and amount as well as compatibilization on mechanical properties have been investigated. Ultimate tensile strength was found to be consistent across different manufacturing methods and after aging; tensile modulus was more dependent on manufacturing method and TPS formulation. High-amylose starches improved mechanical properties at low plasticizer contents but hydroxypropylation did not. Small amounts of compatibilizers improved strength and stiffness; larger quantities of octenyl-succinic anhydride modified starch improved consistency while preserving strength, stiffness and ductility. The highest blend strengths, as well as lowered ductility, were found in strand tests where TPS/PE modulus approached that of the PE.