| Film, ground film and packing materials possess a large proportion in plastic garbage. To replace them with film material with good degradability can alleviate the white pollution and the petroleum resource shortage. Starch-based biodegradable plastic film is a kind of important degradable polymer material. This paper will focus on how to improve the mechanical properties and water-resistance of the material, at the same time ensuring its biodegradability. The major work includes the preparation of phosphate porous starch and the starch-film.Porous starch has more surface area and hydroxyl group than native starch. In this paper it has been proved that many properties of starch and starch material, such as freeze-thaw stability, resist shearing, heat-resistant stability, and consistency with PVA, can be improved greatly when starch is modified by hydrolytic and phosphorylation, and many properties of starch film, such as tensile strength, water-resistance and biodegradability also can be improved greatly when metamorphic starch is cross linked, plasticized, strengthened at the same time.1 The optimum hydrolytic conditions were as follows: pH 5.2, the quantity ofα-amylase 1%, reaction time 6h, reaction temperature 50℃.2 By means of quadratic component rotational design, the experiment was conducted in order to get an optimized preparation scheme for degree of substitution (DS). Y=-2.2814-0.02248Z1+0.02436Z2+0.3202Z3+0.00268Z4+0.3881Z5+0.00376Z1Z2-0.00357Z1Z5+0.00335Z2Z3+0.01132Z2Z4-0.00171Z3Z4-0.04016Z3Z5-0.00631Z4Z5+0.00147Z12-0.00290Z32。3 The optimum preparation starch film conditions were as follows: starch: PVA was 7:3, water 15%, glycerol 20%, polymeric glycol 15%, methenamine 1.5%, boric acid 2%, glyceryl monostearate 0.6%, urea 3.5%.4 By means of quadratic component rotational design, the experiment was conducted in order to get an optimized preparation scheme for starch film. Y=-1374.78+13.43Z1-7.31Z2-46.13Z3-0.52Z1Z3+0.87Z2Z3-0.24Z22。5 The structural characteristics of the films were investigated by infrared spectroscopy(IR) and X-ray diffraction. The results demonstrated that: phosphate groups were linked with the anhydrous glucose units. Phosphate porous starch and PVA were cross linked by methenamine and boric acid Crystal area was serious destroyed by esterification and cross linked.6 Biodegradation experiment was carried out with soil-burying method. The result showed that the ratio of lose weight of starch film is 60% after 150 days under the soil.
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