Development of co-continuous morphology in blends of thermoplastic starch and low-density polyethylene.

This study focuses on the morphology development in blends of thermoplastic starch (TPS) with Low Density Polyethylene (LDPE) in the 40 to 80 TPS wt% concentration range. The effect of glycerol and water content on TPS rheology and the subsequent morphology development after blending with LDPE of various viscosity levels was investigated. The TPS/LDPE viscosity ratio was modified either by increasing the TPS plasticization or by proper selection of the LDPE grade. Particular attention was given to the effect of TPS humidity on viscosity and therefore humidity levels were carefully measured by Karl Fisher titration prior to rheometry. It was found that the viscosity of the TPS was highly dependent on the plasticizer level and that the flow activation energy of TPS was around 3 times higher than that of LDPE. Different types of blend morphologies were achieved from dispersed to co-continuous. It was found that the co-continuous structure appeared at higher TPS concentration when increasing the TPS/LDPE viscosity ratio.