【作者】 熊汉国；

【导师】 谢笔钧；

【作者基本信息】 华中农业大学 ， 食品科学， 2008， 博士

【摘要】 随着石油短缺带来的能源危机和废弃塑料引起的“白色污染”日趋严重,对天然生物质材料的研究愈来愈引起各国政府和科学家们的重视与关注。淀粉这类来源广泛的天然高分子多糖,则是生物质材料较理想的选择之一。然而由于淀粉自身的多羟基结构和结晶规整排列,以及由此带来的许多特性,限制了直接将淀粉用于加工或代替塑料薄膜和其它用途的制品,特别是农用地膜,难度更大。为此,本文以淀粉为原料,选用不同的增强剂制备全生物降解包装膜、农用地膜和宠物玩具。根据加工材料的需要,选择不同粒度大小的淀粉,并对其进行特殊的物理和化学修饰,使淀粉分子链形态适应其加工性能。主要研究结果如下:1.纳米二氧化硅改性淀粉基生物降解包装膜的机理通过IR、XPS、XRD及DSC分析技术对纳米二氧化硅改性淀粉基生物降解包装膜的微观结构、原子组成变化、聚集态行为及热特性进行表征和分析,探讨了纳米二氧化硅改性淀粉基生物降解包装膜的机理:纳米二氧化硅不仅同ST和PVA分子间形成氢键,同时还通过化学键作用形成新的C-O-Si键,从而使纳米二氧化硅与ST-PVA分子间形成致密的网络结构,进一步揭示了纳米二氧化硅提高ST-PVA膜性能的本质原因。2.纳米二氧化硅改性淀粉基生物降解包装膜的制备技术系统的研究了纳米二氧化硅的分散方法以及淀粉的增塑和交联技术。研究结果表明超声波分散方法是分散纳米二氧化硅较理想的分散方法,选用脉冲式(开启3s,停止2s)及超声波振幅为50%的条件下,超声波处理纳米二氧化硅12min,可使纳米二氧化硅均匀的分散在ST-PVA膜中;纳米二氧化硅的最佳添加量为1.5%,可以显著提高ST-PVA膜的耐水性、拉伸强度、断裂伸长率以及在环境中的适应性能;通过正交实验及模糊数学中的综合评价法,确定了三种复合增塑剂水、乙二醇和丙三醇的最佳用量分别为水4%、乙二醇3%和丙三醇9%;乙二醛是淀粉的有效交联剂,乙二醛交联反应的优化条件为乙二醛2.5%、pH为9、反应温度为80℃及交联反应时间为30min;淀粉基生物降解包装膜的力学性能达到国家标准GB/T4456-1996(包装用聚乙烯吹塑薄膜国家标准),并具有很好的环境适应性能和生物降解性能。3.微细化淀粉的特性及其在生物降解地膜中的应用利用超声波气流粉碎机制备微细化淀粉,并进一步对微细化淀粉进行疏水化改性,以提高与PCL生物降解高分子材料的相容性。研究结果表明淀粉经微细化处理后,粒径明显下降,表面变得不规则,并且随微细化程度的提高,淀粉分子内的氢键断裂程度提高,淀粉分子表面活性提高以及结晶度下降,经进一步研究发现,过细的淀粉易发生聚集现象。结合成本考虑,选择300目的微细化淀粉较适宜;采用双重增塑改性,确定了PCL增塑改性的条件为增塑剂PEG(Mn=6000)用量为6%,淀粉增塑改性的增塑剂的最佳用量为三乙醇胺4%、聚乙二醇(Mn=400)3%及丙三醇2%;经在甜玉米作物进行田间实验结果表明,淀粉基生物降解地膜具有保温、保水及增加农作物产量的作用,且具有较好的生物降解性能,可以替代非降解性的PE地膜。4.淀粉的双酯化改性及其在宠物玩具中的应用较系统的对磷酸化醋酸化双酯化淀粉的微观结构、热特性及晶体结构特性进行了研究,并通过进一步的增强、增塑及交联制备可食性宠物玩具。研究结果表明淀粉经双酯化后,其透光率提高、冻融稳定性和膨胀度增加,双酯化后的淀粉较原淀粉结晶度下降,而保水性和热稳定性提高;当复合增塑剂水和丙三醇用量各为12%、交联剂多聚磷酸钠用量为2%、增强剂明胶用量为20%时,制备的宠物玩具硬度为14042.55g和弹性为0.936。主要创新点:1.利用纳米二氧化硅高表面活性的特点,采用超声波分散后用来改性淀粉,从而提高了淀粉基包装膜的性能;发现纳米二氧化硅与ST-PVA间存在氢键及化学键合,探索了纳米二氧化硅提高ST-PVA包装膜的机理。2.根据热力学原理,利用机械力作用,降低淀粉颗粒的结晶度和簇聚行为,使淀粉无序化程度和反应活性增加,通过具有高反应活性的双氨基硅烷对微细化淀粉进行疏水化改性,同时对微细化淀粉和增强剂PCL进行双重增塑,利用吹膜法成功的制备了具有良好机械性能和降解性能的全生物降解地膜。3.将淀粉进行双酯化改性后用于制备淀粉基宠物玩具,并采用物性测试仪对淀粉玩具的质构特性进行表征。更多还原

【Abstract】 Recently,natural biomaterials have received increasing attention in many counties and by a number of scientists,especially the topics of energy crisis aggravation and environmental pollution.Starch,as an abundant raw material,has been used in the field of biomaterials,but the application of raw starch in the preparation of starch-based biomaterials such as packaging films and agricultural plastic films is limited because of its multi-hydroxyl and regular crystal structure of native starch gragules.In this paper, full-biodegradable films,agricultural plastic films,and pet toys were prepared by using starch with different sizes,modified starch and intensifiers.The structures of various biomaterials were characterized by Fourier transform infrared spectrometry（FTIR）, differential scanning calorimetry（DSC）,X-ray photoelectron spectrometry（XPS）,X-ray diffraction（XRD）,and scanning electron microscopy（SEM）.And at on time,the mechanism of starch modification was discussed.The main contents,results and conclusions of thesis are as follows:1.The mechanism of modified starch-based biodegradable packaging film using nano silicon dioxide（nano-SiO₂）The microstructure,atoms constitute aggregation,and thermal properties of a modified starch-based biodegradable packing film with the addition of nano-SiO₂ were characterized and analyzed.The mechanism of modification was also discussed by FTIR, XPS,XRD and DSC:not only extensive intermolecular hydrogen bonds but also C-O-Si bonds were generated among nano-SiO₂ and starch-PVA;therefore,a dense network structure was formatted among the molecules of nano-SiO₂,starch,and PVA.Further results revealed the essential reasons for the improved properties of the ST-PVA film using nano-SiO₂.2.The preparation technology for a starch-based biodegradable packing film modified by nano-SiO₂The paper systematically studied the dispersion method of nano-SiO₂ and the plasticization and crosslinking technology of starch.The results indicated that ultrasonic dispersion was a good method for dispersing nano-SiO₂.Nano-SiO₂ could homodisperse in ST-PVA films under the condition of pulsing on 3s,pulsing off 2s,and 50%swing intension for 12 min.Since the optimum content of nano-SiO₂ was 1.5%, then the water resistance,tensile strength,breaking elongation,and environmental suitability of ST-PVA films could be obviously improved.The optimal contents of compound plasticizers were determined with water（4%）,glycol（3%）,and glycerol （9%）,respectively by employing orthogonal experiment and comprehensive assessment method in fuzzy mathematics.Glyoxal was an effective crosslink agent to starch.The optimal crosslinking conditions are the following:glyoxal content of 2.5%;pH 9; reaction temperature at 80℃;and reaction time of 30 minutes.The mechanical properties of the starch-based biodegradable packing film reached the Chinese standard of GB/T 4456-1996（the Chinese standard of polythene packing film）,and these products had great environment suitability and biodegradability.3.The properties of micronized starch and its application in biodegradable filmTo improve the miscibility of starch and PCL,micronized starch was prepared by an ultrasonic airflow pulverator,then it was hydrophobically modified.The results showed that the particle size of starch decreased obviously,and the surface became irregular.With the micronization degree increasing,the hydrogen bonds were fractured within starch molecules,the surface activity of the starch molecules was increased,and crystallinity was decreased.However,further research indicated that excessive micronization would make aggregate starch.Micronized starch of 300mu was suitable considering the production cost.The conditions of double plasticization modification determined that the content of polyethylene glycol（PEG）（Mn=6000） as a PCL plasticizer was 6%according to the weight of PCL,and the optimal content of triethanolamine was 4%,polyglycol （Mn=400） 3%,and glycerol 2%as starch plasticizers according to weight of ST, respectively.The field experiment results of sweet corn crops showed that the starch-based biodegradable films,which could substitute for the non-degradable PE film, had effects on performance in terms of heat retention,water retention,preferable biodegradability,and increased yield.4.The diesterified starch and its application in pet toyThe microstructure,thermal properties,and crystal structure of diesterified starch, namely,the starch of phosphorylation and acetification,were studied systematically.The pet toys were prepared by further treatment in terms of enhancement,plasticization,and crosslinking.The results indicated that the transparency rate was improved,and the freeze-thaw stability and degree of expansion were also increased.The crystallinity of diesterified starch decreased compared with natural starch.However,water retention and the heat-resistant stability of starch were improved when the content of the compound plasticizers of water and glycerol were 12%,respectively,the crosslink agent of polyphosphate was 2%,the intensifiers of glutin were 20%according to the weight of double-esterification starch,and the hardness and elasticity of the pet toy were 14042.55g and 0.936,respectively.The creative achievements of this work were as follows:1.Starch was modified by nano-SiO₂ with high surface activity which was dispersed by ultrasonic dispersion,and the properties of the starch-based packaging film were improved.Furthermore,it was found that a hydrogen bond and a chemical bond exist among nano-SiO₂ and starch-PVA.2.According to thermodynamic principles,the crystallinity and clustering behavior of starch particles were decreased.The disordering and reactivity of starch were increased by mechanical force action.Micronized starch was yielded through the modification of hydrophobicity and double plasticization,and the full-biodegradable films with good mechanical and degradable properties were prepared using the film blowing method.3.Starch-based edible pet toy was prepared using diesterified starch,The texture properties of starch pet toy were characterized by a texture analyzer.更多还原