Studies On The Influence Of Organic Acid On The Performance Of Thermoplastic Starch/Polyethylene Blend

The development and the state of the biodegradable materials based on starch was concluded in this paper at first, and the thermoplastic starches/ polyethylene blends still be wildly used. At same time we conclude the problems of this blends and point out how to extrude the blends at "one-step". So something as additive to realize the starch to be completely plasticized by glycerol must be used at the present of PE to improve the ability of dispersed and compatible between two incompatible phases. The high performance green biodegradable materials can be easily achieved at low price. At the first step of this work, the "one-step" extrusion process with "two-step" extrusion process was compared and the extrusion times both have great influence on the TPS/PE blends in the morphology structures and the mechanical property. So we can make a conclusion that the extrusion process of TPS was great influenced with the present of synthetic resin. At the same time it can be certain that the ability of dispersed and compatible between two phases is bad. In order to improve this limitation, the morphology structures and the mechanical property of the TPS/PE blends at the present of different organic acids in the "one-step" extrusion process was studied. At last it was curtained that the citric acid (CA) can greatly improves the morphology structures and remarkably increases the mechanical property of the TPS/PE blends. At the second step of this study, the influence of CA on the TPS/PE blends further more and certain the optimal content of CA in the TPS/PE blends was studied. Different properties were examined including mechanical properties, scanning electron microscopy (by SEM), thermal properties (by TG), rheological properties, crystallinity properties in the extrusion process and water resistance (under different imitated RH environments). The results show that the blends with CA have better mechanical properties and thermal properties than those without CA. By SEM analysis, the addition of CA improved the mutual disperse of TPS and PE, and there also isn't obvious phase interface. So TPS and PE formed an evenly continuous phase system on the whole. By the rheological analysis, the addition of CA decreased the viscosity of the blends, improves the flow behavior of the blends, and further improves the machining properties. The X-Ray diffraction results showed that the crystal structure of starch was destroyed more completely after it was thermal plastecized with the CA appended in the single-screw extruder than without it at the present of PE. The crystal structure of PE is obvious decreased with the increasing of the mutual disperse of TPS and PE. With the addition of CA, water resistance of the blends increase to some extent. At last the effects of CA on the properties of glycerol-plasticized thermoplastic starch (GPTPS) were studied in this paper, still as the mechanism of the TPS/PE blends. Different properties were examined including mechanical properties, scanning electron microscopy (by SEM), thermal properties (by TG), rheological properties, crystallinity properties in the extrusion process and water resistance (under different imitated RH environments). The results show that the blends with CA have better mechanical properties and thermal properties than those without CA.