气凝胶调控玻璃棉芯材孔结构及其VIP热导率气压敏感性研究

The manned bathyscaph is major equipment for China's future marine strategy. In order to adapt to the cold environment of 0~6°C in the deep sea, the ultra-low thermal conductivity ultra-thin structural insulation material is the key to achieving its 50-year safe service. The vacuum insulation panel (VIP) with glass wool as the core material has a thermal conductivity of less than 3 mW/(m·K), which achieves the same thermal insulation effect as the traditional thermal insulation materials, but its thickness is 10 to 20 times less, showing significant advantages. However, it can only work effectively for 5 to 15 years under a pressure of 300 Pa because the microporous core material is very sensitive to air pressure. This project focuses on introducing nano-hybrid aerogel into glass wool core material to regulate pore size of the core material to sub-micron level and thus to increase VIP critical pressure and VIP theoretical service life to 3000 Pa and 50 years, respectively. Irradiation is carried out during the semi-gel process of the precursor to crosslink the vinyl groups uniformly dispersed in the gel to form a spatial network structure interlaced with the Si-O-Si wet gel network. Photosensitive monomer is formed on the surface of the wet gel colloidal particles. A novel and high-strength SiCO aerogel is fabricated after drying, which solves the problem that the aerogel is brittle and easy to drop powders. The aim of this project is to find out the regulation mechanism that can reduce the thermal conductivity and improve service life of VIP simultaneously, and provide basic materials and new thermal insulation and energy saving solutions for the development of manned bathyscaph.

载人深潜器是我国未来海洋战略的重大装备，为适应深海0～6℃寒冷环境，超低热导超薄结构保温材料是实现其50年安全服役的关键。以玻璃棉为芯材的真空绝热板（VIP）热导率低于3mW/(m·K)，达到同样保温效果，其厚度仅是传统保温材料的1/10～1/20，具有显著优势，但因芯材孔径为微米级而对气压非常敏感，只能在300Pa以内有效服役5～15年。本项目拟将纳米杂化气凝胶引入玻璃棉芯材，调控芯材孔径至亚微米级，使VIP临界气压提升至3000Pa，VIP理论服役寿命提升至50年。在前驱体的半凝胶过程中进行辐照，使均匀分散在凝胶中的乙烯基交联，形成与Si-O-Si湿凝胶网络交错互联的空间网络结构，并将光敏单体敷形于湿凝胶胶粒表面，干燥后形成高强韧的SiCO新型气凝胶，解决气凝胶脆性大、易掉粉难题。探明既能降低VIP热导率又能提高其服役寿命的调控机制，为载人深潜器的发展提供基础材料和保温节能新方案。

本项目针对载人深潜器等国防、民用装备对高性能、高耐久绝热材料的需求，提出一种以气凝胶/玻璃棉复合材料为芯材、超低热导超薄结构的真空绝热板及其制备方法。主要研究了气凝胶改性玻璃棉芯材的孔结构调控机制、芯材孔结构对真空绝热板热导率的气压敏感性影响和湿热环境对真空绝热板的老化机理。结果表明，以溴化十六烷基三甲铵（CTAB）/去离子水为溶剂，甲基三乙氧基硅烷（MTES）为硅源，醋酸为酸催化剂，氨水为碱催化剂，可制成轻质（100-130kg/m3）、低收缩（5-20%）和低导热（34.55-40.36mW/(m·K)）的聚甲基硅倍半氧烷（PMSQ）气凝胶。溶胶中CTAB和MTES的最优含量为0.866mmol/L和1.062mol/L，制得的PMSQ气凝胶的压缩强度为0.205MPa，能承受至少10次50%循环压缩，疏水角为155.6o，初始分解温度为565℃。经参数优化后，本项目研制的PMSQ气凝胶的制备周期为19h，仅为传统工艺合成时间的1/32至1/1.3，且不包含溶剂置换和表面修饰等高污染、高耗时环节。通过溶胶-凝胶法在MTES溶胶中掺入六水合氯化铝后，利用同样工艺可实现将其压缩强度、压缩应变和初始分解温度分别提升至0.36MPa、71.4%和625℃。甲基三甲氧基硅烷（MTMS）溶胶与壳聚糖溶胶最优的复配比例为1:1，反应时间为24h，制得的复合气凝胶不仅能在各种模具中成型，还能切角、钻孔，其线性收缩率和压缩强度分别为3.3%和1.44MPa。将玻璃棉与PMSQ气凝胶复配，其压缩强度可提升至0.45MPa，热导率为32.6mW/(m·K)，密度为165kg/m3，平均孔径为150 nm。将玻璃棉/PMSQ气凝胶进行抽真空、膜材封装处理，可制得真空绝热板，其热导率可低至4.8mW/(m·K)，临界压强为43000Pa。将真空绝热板置于30℃、60%R.H.的环境下进行抗老化性能测试，结合理论和实验数据分析，表明：内部气压对真空绝热板热导率的平均增量为0.3mW/(m·K)/年，水分含量对真空绝热板服役初期前12年和第13-50年热导率的平均增量为0.17mW/(m·K)/年和0.01 mW/(m·K)/年。本项目通过优化气凝胶的成分和制备工艺使气凝胶/玻璃棉真空绝热板既具有低热导率又具有长使用寿命，可为载人深潜器等国防、民用装备的发展提供基础材料和保温节能新方案。