| Starch/Poly(Lactic Acid) composite, as a kind of new totally biodegradable plastic with a bright foreground, take a balance between the high performance of Poly(Lactic Acid) and the inexpensive of starch. This composite can not only economize petroleum resources, but also develope a new nonfood use of starch. However, native starch is hard to be melted, so generally, starch granule is hard to be melted and mixed homogeneously with Poly(Lactic Acid) in blends. That could lead to poor mechanical properties and limit the starch content of the blends.In this study, thermoplastic starch with different glycerol/starch mass rates were prepared by twin-screw extrusion, and standard samples of thermoplastic starch/Poly(Lactic Acid) composites with different Poly(Lactic Acid) contents and glycerol/starch mass rates were injection-molded. In order to evaluate the influence of glycerol/starch mass rate and extrusion parameters on thermoplastic starch, the extrusion torque, viscosity properties and TG/DTA curve of each thermoplastic starch samples were studied. And the tensile strength, elongation at break, flexural strength, flexural modulus, water absorption rate, water resistance index (R) and TG/DTA curve of thermoplastic starch/Poly(Lactic Acid) composite samples, which could evaluate the influence of Poly(Lactic Acid) content and glycerol/starch mass rate on the composite's properties, also be studied. The conclusions can be drawn as follows: For thermoplastic starch, its thermoplastic properties of starch could be improved with the rise of glycerol/starch mass rate. And the extrusion parameters also have influence on thermoplastic properties of starch. On the condition that glycerol/starch mass rate is 2/5, Zone3's temperature is 130℃, Zone5's temperature is 110℃～125℃and the screw speed is 80rpm, thermoplastic starch with a high thermoplastic properties could be prepared at a low cost.For thermoplastic starch/Poly(Lactic Acid) composites, with the Poly(Lactic Acid) content increase, its tensile strength, elongation at break, flexural strength and flexural modulus could be enhanced. Glycerol could weaken the tensile strength of composites, but with the glycerol/starch mass rate increasing, their tensile strength and elongation at break could be enhanced. Flexural strength could increase as the glycerol/starch mass rate increases, but the result were opposite for flexural modulus. Relatively, the effect of the Poly(Lactic Acid) content on tensile properties was more notable, and the effect of the glycerol/starch mass rate on flexural properties was more notable.For thermoplastic starch/Poly(Lactic Acid) composites, the increase of thermoplastic starch content could lead to its water resistance properties worse. However, this tendence could be prevented by the glycerol/starch mass rate increase, and this effect was more remarkable as the thermoplastic starch content increased. The composites had a good thermal stability. Their glass transition temperature is not influenced by Poly(Lactic Acid) content and glycerol/starch mass rate, but melting temperature could reduce a little as the Poly(Lactic Acid) content and glycerol/starch mass rate increased.
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