NATIVE STARCH USED FOR MODIFICATION OF SYNTHETIC-POLYMERS

New compounds were developed by modifying synthetic polymers with starches. The resulting property profiles allow applications which are not accessible for the initial materials. Three different categories of compounds were produced by use of a corotating, intermeshing twin screw extruder and characterized with regard to their physical and mechanical properties. The first category includes materials which contain starch in their native grain form as a functional filler. The property profile depends on the interaction between the starch surface and the matrixpolymer, which can be improved by an organosilane coating. The two other categories are based on destructurized starch. The starch is modified in the twin-screw kneader by a thermomechanical desintegration of the macroscopic starch granules and under the addition of plasticising and softening agents. The created thermoplastically processable moulding compounds can be used directly as a material for special applications. However the more important application of such thermoplastic starches (TPS) is all area of blending or alloying with synthetic polymers. In combination with ethylencopolymers, compounds are obtained, in which TPS forms the disperse phase. Despite of its higher content in the blend, the TPS is embedded in the synthetic polymer matrix, forming small and discrete distributed particles. The resulting microstructure and morphology strongly affects the properties of the blends.