双层共挤出法制备二氧化硅气凝胶纤维长丝的研究

Silica aerogels, with a special three-dimensional nanostructured networks, are considered as the best insulation materials in the present because of their extremely low thermal conductivity. However, their inherent fragility and weak mechanical strength have restricted the use of monolithic aerogels. So, the mechanical performance must be improved. By the traditional modification method, unfortunately, it is hard to acquire ideal effects both in the insulation and mechanical properties. Additionally, due to the rigid frame of modificated materials, the reprocessing feature is too weak to meet the real needs of applications.In this study, combining with the ambient pressure drying process, the silica aerogel fiber will be prepared with commercial waterglass as silica precursor via the dual-layer coextrusion method. The silica aerogel fibers, designed as an outer surface of silica aerogel with low thermal conductivity and an inner polymer partition with high mechanical strength, may anticipate to be used as an ideal flexible composite insulation material.The performance of silica aerogel fibers is determined by the integrity of the monolithic silica aerogel in the outer fibers surface together with the forces between the outer and inner interface. In order to get a monolithic silica aerogel in the fiber surface, a template agent will be introduced to the solution of silica precursor and removed in the ambient pressure drying process after the silica gel formation. Furthermore, by associating with the graft modification in inner polymer and the organic modification in the silica gels, an effective chemical bonds can be formed between the outer and inner interface.Taking advantage of the good molding processibility of polymer materials, a composite aerogel fiber with high mechanical properties and excellent insulation performance can be easily achieved. At the same time, a thinner structure of silica aerogels in the outer fiber surface could shorten the fabrication period during the ambient pressure drying process. Moreover, the thinner structure is easy to be further functionalized,which would expand the scope of application of the silica aerogels.

要制备具有实用价值的SiO2气凝胶隔热材料必须对其进行增强、增韧。本研究以工业水玻璃为硅源，利用常压环境干燥工艺，结合有机高分子聚合物纤维成型技术，采用双层共挤出法制备以SiO2气凝胶为面层、以有机高分子聚合物为芯层的连续SiO2气凝胶长丝，以获得具有良好柔性、优良后加工性且自身具有良好力学性能的SiO2气凝胶纤维型柔性复合隔热材料。SiO2气凝胶自身的纤维化，面层气凝胶块体的完整性以及面层和芯层之间的界面效应，是决定其性能的关键因素。为保证面层凝胶体的完整性，成型过程先辅助以模板剂，待湿凝胶形成后结合常压环境干燥过程中的溶剂交换和表面疏水改性脱除模板剂。同时利用芯材基体的化学改性和面层凝胶体的有机改性，可在芯层聚合物和面层气凝胶之间形成有效共价键合作用，增强面层和芯层之间的结合力。常压环境干燥条件下，气凝胶自身纤维化的实现，使其作为整体化的复合材料在民用保温节能领域具有重要应用价值。

本研究以工业水玻璃为硅源，利用常压环境干燥工艺，结合有机高分子聚合物纤维成型技术，采用双层共挤出法制备以二氧化硅气凝胶为面层、以有机高分子聚合物为芯层的连续二氧化硅气凝胶长丝，以获得具有良好柔性、优良后加工性且自身具有良好力学性能的二氧化硅气凝胶纤维型复合隔热材料。. 首先采用溶出置换工艺，以工业水玻璃作为原料，探索了应用含有不同基团高分子聚合物溶出置换合成二氧化硅气凝胶的新方法，并采用FI-IR、SEM、TEM、XRD、TG-DSC等对成型样品的结构和性能进行了表征。实验结果表明与水溶性聚合物的先溶出置换方法相比，后溶出置换法合成的二氧化硅凝胶能够形成更高孔隙的三维网络结构；采用 PAM、PEG、PVA溶出置换合成的SiO2气凝胶颗粒或团簇平均直径 10-20 nm，平均孔径18nm；当以聚乙二醇(PEG10000)为添加剂时，制备获得的二氧化硅凝胶体比表面积可达568 m2/g。. 针对纯质二氧化硅气凝胶脆性大、常压环境干燥条件下难以获得完整块状结构的缺点，研究了不同硅烷偶联剂存在条件下甲基丙烯酸甲酯(MMA)有机改性二氧化硅气凝胶的系列性能。改性成型二氧化硅气凝胶13C-NMR 和FT-IR的测试结果表明聚合物聚甲基丙烯酸甲酯和二氧化硅胶体颗粒之间形成了有效的键合作用；力学性能的测试结果表明，当改性溶液中聚合物的浓度为50%时，与纯质二氧化硅气凝胶相比改性样品的杨氏模量和硬度分别增加了12倍和61倍；改性聚合物的引入虽然增加了成型样品的本体密度，但有效减小了二氧化硅湿凝胶在常压环境干燥条件下的收缩性；改性聚合物的引入为二氧化硅气凝胶的增强增韧提供了一种新的方法。. 最后，以PAN聚合物为芯材，以二氧化硅凝胶体为面层，研究了共挤出工艺对纤维体性能的影响。常温环境干燥条件下，气凝胶自身纤维化的实现，使其作为整体化的复合材料在民用保温节能领域具有重要应用价值。.