纳米二氧化硅有机胡须的拓扑结构及对PET结晶成核效应的研究

Poly (ethylene terephthalate) (PET) as an organic synthetic material holds the leading position in the synthetic polymer. However, its crystallization rate is too slow that induce the structural imperfect, long processing cycle, low production efficiency, and high energy consumption. Through the surface grafting of inorganic nano-particles (such as SiO2) by epitaxial topology in ths proposal, the block oligomer haired nano-SiO2 particles will be synthesized, in which the organic hair is the diblock oligomer that has soft segment and a PET segment. With the nucleation effect of the haired nano-SiO2 on PET resin, the PET crystallization rate or temperature will be raised by more than 20 ℃, and thus imparts the good processing and forming performance to PET materials. By the structural changes of haired nano-SiO2, the comprehensive mechanical and physical properties of the molding PET materials (just like fiber or injection molded specimen) will be improved obviously, including the strength, elongation, modulus and optical transparency. The key innovation point is that the surface grafting at inorganic nano-particles (such as SiO2, etc.) by the block oligomer hair with both a soft segment and a PET segment, and the bulk PET crystallization rate can be increased by the epitaxial PET oligomer -crystallized seed.

聚对苯二甲酸乙二醇酯（PET）在合成高分子中占有领衔地位的有机合成材料。然而结晶速度太慢造成结晶不完善，致使加工周期长，降低生产效率，浪费加工能源。本项目通过无机纳米粒子（如SiO2等）的表面接枝，合成具有软段和PET段的两嵌段齐聚物胡须包覆的纳米SiO2蒙皮粒子，通过外延拓扑合成嵌段齐聚物。通过胡须化纳米SiO2的对PET树脂的成核效应与PET结晶动力学研究，使PET的结晶温度大大提高，进而，获得良好的复合材料加工成型性能；通过研究胡须化纳米SiO2的结构变化，获得成型的PET材料（如纤维或注模试样等）的强度、伸长、模量及光学透明性等综合力学和物理性能。最终获得胡须化纳米粒子诱导PET结晶成核效应的科学规律和可用技术。其创新点在于无机纳米粒子（如SiO2等）表面合成具有软链段和PET链段的两嵌段齐聚物胡须，通过外延PET齐聚物晶种的办法诱导本体PET结晶，进而提高结晶速率。

采用不同结构的嵌段聚合物接枝改性纳米SiO2，嵌段在纳米SiO2表面生长并向外延伸，形成多组元聚合物“胡须化”的结构特征。胡须嵌段在SiO2表面形成拓扑聚集态结构；胡须化纳米SiO2对PET的结晶行为产生影响；随着胡须化纳米SiO2的加入及添加量的增加，复合体系的晶粒数明显增加，晶粒尺寸明显细化变小，晶体大小尺寸更均匀，晶粒排列更致密，缺陷减少。复合材料的结晶温度、熔融温度均比纯PET的高，同时用复合材料的熔融热焓计算得到的复合材料的相对结晶度随改性纳米二氧化硅的添加量的增加而逐渐增大。添加胡须化纳米SiO2对PET复合材料的综合力学性能影响：嵌段齐聚物修饰硅球含量在一定范围内（≤2.5%质量分数）时，可以让材料的模量和伸长率及拉伸强度都增加。大约纳米粒子含量大约在2%时PET的综合机械性能最优。