| Nowadays, the small-size effect of micronized starch is widely noticed, and it is of great significance to bettering starch based degradable plastic properties and improving weight content of starch. In viewing of this, with starch of corn as row material, micronized starch was prepared by modern powder equipment. The properties and aggregate-state structure of micronized starch were charactered. The influences of starch granularity effect on the morphological structure, mechanical properties and environmental degradable property of degradable materials were mainly studied and also the relation between microcosmic structure of micronized starch and its macroscopical properties was discussed. Subsequently, high-content starch based environmental degradable blow film and full-biodegradable composite sheet were prepared. The main conclusions lies in:1. Studies on starch granularity effect, properties of micronized starch and its structureAdopted the supersonic blast air current pulverizer, 4 grades micronized starch(MST-l, MST-2, MST-3, MST-4) were prepared and their d50 were 7.12 n m, 4.56 u m, 3.17 11 m, 3.03 u m, and distributions were 0.039, 0.033, 0.043, 0.046 respectively. The research through SEM, LCSM, GPC, LLS, Polarized Microscope, XRD, DSC,,ESCA showed that the granularity effect had strong influence on the microcosmic shape and morphological structure of micronized starch. The reactive property of micronized starch molecules were improved due to its small-size effect. The amylopectin and the surface of micronized starch granule were readily broken with the mechanical force. Whereas the proportion of amylose increase and the molecular flexibility was improved. The crystallinity of ST, MST-1, MST-2, MST-3, MST-4 were respectively 38.37%, 31.14%, 28.12%, 26.71%, 25.33%. LCSM showed that the crystal core of starch altered little.2. Dry-method hydrophobic modification of micronized starch and structural characterAdopted coupling agent DL, dry-method hydrophobic modification was conducted. The reduction of starch granularity improved the modification degree. The optimized conditions for MST-4 modification were: 112℃, 20min, 1.9%DL. SEM and Laser Method showed that the surface of modified MST-4 was smooth, and its dso increased slightly but the distribution was still narrow. IR and ESCA showed that the modification was a kind of chemistry reaction, and the small-size effect of micronized starch deepened the reaction.3. Preparation of micronized starch based environmental degradable blow film and its structureThe starch granularity effect had great influences on the properties and morphological structure of MST/LDPE blend system. The lower the starch granularity was, the smoother the MST/LDPE film was. Rheological analysis showed that MST/LDPE blend melt was pseudoplastic fluid, and it had yielding behavior. The mechanical property, environmental property and other physical properties ofMST-4/LDPE were optimum. The Starch based environmental degradable matrix formulas were: 78%~80%MST-4, 1.9%~2.0%DL, 2.5%~2.7%dispersant, 16%~18% carrier LDPE; The content of MST-4 in micronized starch based environmental degradable blow film reached 55%, and its mechanical and environmental properties clearly surpassed the national standard.4. The plasticization of micronized starch and study of thermoplastic full-starch biodegradable matrixRheological analysis showed that thermoplastic starch appeared "sheer-thinning" pseudoplastic property. The mechanical property, DSC, XRD showed that the lower the starch granularity was, the better effect the glycerol/PVA composite plasticizer had, and the higher the disordering degree of thermoplastic starch structure was, thus it melt before its thermal decomposition. Due to the overaggressive effect and overflabby structure of MST-4, the properties of TPS3 was better than' TPS4. And the optimized production conditions of thermoplastic full-starch biodegradable matrix were: glycerol/PVA(v/v)=5:l, 80%MST-3, blending temperature=160℃, screw speed=40r/min.5.
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