【作者】 王富军；

【导师】 陈大俊；

【作者基本信息】 东华大学 ， 材料科学与工程， 2006， 硕士

【摘要】 聚氨酯(PU)是一种含有氨酯基的嵌段共聚物，由于其优良的性能，现已广泛应用于纺织纤维、粘合剂、环保涂料、薄膜和生物材料。然而聚氨酯也存在着断裂强度较小，耐热性能较差的弱点限制了其大规模的应用。近年来，用蒙脱土等硅酸盐粘土增强PU的纳米复合材料逐渐引起了人们的关注，与普通PU相比在力学性能上有了显著的提高，例如高模量、高强度和较好的耐热性能。凹凸棒土(AT)作为另一种硅酸盐粘土，引起了学者的注意，把它作为填充剂以减少聚合物材料的消耗和作为在一些结晶聚合物的成核剂。然而用AT改性增强聚合物的研究目前报道较少，而且用于改性化学纤维几乎未有报道。由于其价格低廉并且性能优越，使其用于改性PU具有广泛的应用前景。本文制备了纳米AT／PU复合材料，通过对不同AT含量改性PU的效果进行研究，探讨了AT对复合材料力学性能的影响，分析了AT／PU复合材料的热分解动力学及耐热性能。通过SEM、FTIR、DMA、DSC等对AT／PU复合材料的结构进行了表征，探讨了AT增强复合材料性能的机理，并提出了AT对复合材料增强作用的结构模型。运用湿法纺丝技术制备了纳米AT／PU纤维，通过AT／PU纺丝液的流变测试，研究了AT对纺丝液和纺丝工艺的影响，并通过力学性能和TGA测试，分析讨论了AT对PU纤维的力学性能和热稳定性的影响。研究结果表明：AT能够以纳米级分散于PU基体中，而且AT与PU硬段发生了相互作用，提高了PU软段的玻璃化转变温度、材料的储能模量和PU硬段的热分解温度，通过橡胶理论分析与计算，比较了AT的加入对提高PU的氢键的活化能和物理交联密度的作用。并且纳米AT／PU材料的力学性能和热性能有了显著的提高，其中AT含量为1.5％样品的断裂强度提高了101％，弹性回复率也有所提高，并且AT含量为1.5％样品的热分解温度提高了近14℃。AT的加入降低了AT／PU纺丝液的粘度，纺丝溶液呈现明显的切力变稀现象。并且提高了纺丝液的粘流活化能，降低了纺丝液的结构粘度指数，提高了AT／PU溶液的可纺性。同时动态流变实验显示复数粘度随着AT的加入逐渐变小，并且储能模量和损耗模量的交点向高频移动，有利于提高纺丝质量。纳米AT／PU改性纤维的热性能和力学性能都有显著的提高。其中AT含量为1％纤维样品的强度提高了31.8％，热分解温度提高了近10℃。更多还原

【Abstract】 Polyurethanes (PU) are a versatile group of multi-phase segmented polymers. It is the widely used materials for fibers, adhesives, protective coatings, membranes and biomaterials due to their excellent mechanical properties, such as high flexibility, abrasion and ductility. However, the low tensile strength and poor thermal stability have been the restriction to enlarge application area of PU. In resent years, clay reinforced polyurethane nanocomposites have attracted much attention because they often exhibit remarkable improvements in mechanical and other properties comparing with common PU, such as increased tensile strength and heat resistant. Attapulgite (AT) is another kind of clay which has lately attracted interests due to its much lower price and more fascinating structure and has been widely used as a filler to reduce the cost of polymer materials and a nucleation agent for some crystalline polymers. However, up to now there are few works have been done on AT reinforced polymer and there is no any works on the chemical fiber modified by AT.In our present wok, we prepared AT / PU nanocomposites with different AT contents by direct blending, discussed the influence of AT on the mechanical properties, the thermal decomposition dynamics and thermal stability of the modified PU. The structure of the nanocomposites was characterized by the SEM, FTIR, DMA, DSC and mechanical test, respectively. The reinforcing mechanism of AT to PU was studied and a structure model of composites was proposed. Also, AT/PU fibers were spun by wet spinning. The rheological behavior of the spinning solution, mechanical properties and thermal stability caused by the effect of AT have been studied. The results are as follows:Nano-sized AT can be well dispersed in the PU matrix, and has an effect on the hard segments of PU. The addition of AT increases the Tg of PU soft segments, enhances the storage modulus of PU and raises the thermal decomposition temperature of PU hard segments. Also, the addition of AT increases the hydrogen bonding activation energy and physical cross-link density. Meanwhile, the addition of AT has a remarkable improvement on mechanical and thermal properties. The tensile strength of the sample with 1.5% AT is about 2.1 times compared with pure PU fibers and the elasticity reversion rates were also increased. The results of TGA experiments showed the thermal decomposition temperature of the sample with 1.5%AT content was increased by 14℃. The static rheological properties of AT/PU spinning solution show that the addition of AT reduces the viscosity and structure viscosity index of the spinning solution, increases the apparent activation energy of flow of spinning solution, therefore, improves the spinning ability. The results of dynamic rheological experiment indicate that the complex viscosity of spinning solution decreases in presence of AT, and the intersection of storage modulus and loss modulus moves to high frequency, which is in favor of improving the quality of fibers. Also, AT has a remarkable effect on the mechanical properties and thermal stability of the modified fiber. The tensile strength of the fiber with 1% AT is about 1.3 times and thermal decomposition temperature increases about 10℃compared with pure PU fiber.更多还原