热塑性淀粉基生物材料共混体系加工性能研究

发布时间：2018-05-14 20:45

本文选题：热塑性淀粉 + 明胶　；参考：《湖北工业大学》2017年硕士论文

【摘要】：淀粉是种来源广泛价格低廉的天然高分子,具有较高的结晶度(20%~45%),淀粉分子之间氢键作用强,限制了分子链的运动,因此淀粉不具备热塑性加工的性能。通过添加小分子的增塑剂,升温和混炼的外界物理因素下,可制备热塑性淀粉材料。但是,热塑性淀粉存在着阻隔性能和机械性能不足,限制其单独作为材料使用。本试验以马铃薯淀粉为原料,丙三醇(甘油),碳酰胺(尿素)为增塑剂、明胶为黏合剂,卡拉胶为增强剂,制备热塑性淀粉(Thermoplastic Starch,TPS)。借助于扫描电子显微镜观察,旋转流变仪分析热塑性淀粉及其共混物的凝聚态结构和影响因素。研究了增塑剂活性基团的不同对热塑性淀粉塑化性能、机械性能、流变性能、热力学性能、微观结构和热稳定性的影响。用亲水性胶体对制备的热塑性淀粉进行热塑共混改性,通过添加明胶、卡拉胶改善热塑性淀粉性能。结果表明天然淀粉通过温度、剪切力与小分子增塑剂的共同作用,使得颗粒结构逐渐消失,最终塑化成类似于塑料的均质结构。增塑剂对淀粉热塑化作用取决于增塑剂分子结构,增塑剂的活性基团和分子量的大小。随着增塑剂用量愈多,增强淀粉热塑化的作用愈显著,增塑后热塑性淀粉的拉伸强度降低,断裂伸长率增加,结晶结构被破坏。甘油组分与尿素组分有不同的吸水过程和平衡吸水率,表现出吸水溶胀的现象,而尿素组分的吸水过程始终是吸水而溶解。综合性能考虑选用20 wt%甘油增塑淀粉制备热塑性淀粉,此时材料的拉伸强度为8.2 MPa,断裂伸长率为25.6%。明胶与TPS共混有利于改善韧性,同时也会增大的密炼机塑化时的平衡转矩。共混物力学性能与明胶含量有关,总的来说,因二者相容性较好,共混物性能得到优化,加入明胶将增加TPS平衡吸水率和吸水速度,吸水率可达627.1%。随着卡拉胶含量的增加,卡拉胶分子可以与淀粉形成更多的氢键,其结果使材料的拉伸强度得到提高,并且导致断裂伸长率逐渐变小。明胶和卡拉胶的链段之间可以通过局部的静电交互作用互相搭接形成一定的网络结构。当共混体系以80:20:10质量分数比例共混时,拉伸强度达到26.62 MPa,断裂伸长率可达73.47%。二者以复配使用能较好改善热塑性淀粉的力学性能,热稳定性及加工性能。
[Abstract]:Starch is a kind of natural polymer with a wide range of low price and high crystallinity. The hydrogen bond between starch molecules is strong which limits the movement of molecular chain. Therefore starch does not have the properties of thermoplastic processing. Thermoplastic starch materials can be prepared by adding small molecular plasticizer, heating and mixing physical factors. However, the barrier and mechanical properties of thermoplastic starch are insufficient, so it is limited to be used as material alone. In this study, thermoplastic starch was prepared from potato starch, glycerol (glycerol, carbamide) as plasticizer, gelatin as binder and carrageenan as reinforcing agent. The condensed matter structure and influencing factors of thermoplastic starch and its blends were analyzed by means of scanning electron microscope and rotary rheometer. The effects of different active groups of plasticizer on the plasticizing properties, mechanical properties, rheological properties, thermodynamic properties, microstructure and thermal stability of thermoplastic starch were studied. Thermoplastic starch was modified by hydrophilic colloid. The properties of thermoplastic starch were improved by adding gelatin and carrageenan. The results showed that the particle structure of natural starch gradually disappeared through the interaction of temperature, shear force and small molecular plasticizer, and finally plasticized into a homogenous structure similar to plastics. The effect of plasticizer on starch thermoplasticization depends on the molecular structure of plasticizer, the active group and molecular weight of plasticizer. As the amount of plasticizer increased, the effect of enhancing thermal plasticization of starch was more obvious. The tensile strength of thermoplastic starch decreased, the elongation at break increased and the crystalline structure was destroyed. Glycerol and urea have different water absorption processes and equilibrium water absorption, showing the phenomenon of water absorption swelling, while the water absorption process of urea component is always water absorption and dissolution. The thermoplastic starch was prepared with 20 wt% glycerol plasticized starch. The tensile strength of the material was 8.2 MPA and the elongation at break was 25.6 MPA. The blending of gelatin and TPS can improve the toughness and increase the equilibrium torque of the mixer when it is plasticized. The mechanical properties of the blends are related to the content of gelatin. On the whole, the blending properties of the blends are optimized because of their good compatibility. The addition of gelatin can increase the equilibrium water absorption rate and water absorption rate of TPS, and the water absorption rate can reach 627.1%. With the increase of carrageenan content, carrageenan molecules can form more hydrogen bonds with starch, which results in higher tensile strength and smaller elongation at break. The chains of gelatin and carrageenan can be overlapped with each other by local electrostatic interaction to form a certain network structure. When the blending system was blended at 80:20:10 mass fraction, the tensile strength was 26.62 MPA and the elongation at break reached 73.47 MPA. The mechanical properties, thermal stability and processing properties of thermoplastic starch can be improved by the combination of the two methods.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O636.12

【参考文献】