Properties of a Biodegradable Ternary Blend of Thermoplastic Starch (TPS), Poly(ε-Caprolactone) (PCL) and Poly(Lactic Acid) (PLA)

Biodegradable ternary blends of thermoplastic starch (TPS), poly(ε-caprolactone) (PCL) and poly(lactic acid) (PLA) were prepared by one-step extrusion based on the complementary mechanical properties between both ductile PCL and rigid PLA and also low cost TPS. TPS/PCL/PLA blend was prepared using equal mass fraction of each component and presented as an incompatible material. We then evaluated the addition of citric acid, maleic anhydride and methylene diphenyl diisocyanate (MDI) as compatibilizing agents in the ternary blend. They did not significantly affect thermal stabilities of the ternary blends but induced PCL and PLA crystallization. Adding 2 wt% of MDI caused an increase in melt viscosity of the ternary blend suggesting that urethane linkages were formed with TPS and it also was efficient in order to obtain notable improvements in tensile strength and ductility of the ternary blend.