对位芳纶气凝胶的制备及其孔结构调控

Preparation of para-aramid aerogel and its pore structure regulation

针对冷冻干燥条件下气凝胶骨架易坍塌而造成隔热效果差的问题,配制二甲基亚砜(DMSO)与四丁基氟化铵(TBAF)溶液溶解对位芳纶纤维;通过改变叔丁醇/水置换液的体系构成来调控气凝胶的孔结构,制备隔热性能优异的对位芳纶气凝胶,并对该气凝胶的表观形貌、微观结构、热稳定性以及导热系数进行测试表征。结果表明:与纯水为置换液相比,加入叔丁醇可改变冰晶的生长形态,使得气凝胶内部呈现均匀的三维网状孔结构,有效改善了其骨架坍塌的问题。随着置换液中叔丁醇体积分数的增大,气凝胶收缩率先减小后增大,导热系数呈现相同的趋势;当叔丁醇体积分数为50%时,气凝胶收缩率最小,密度为0.021g/cm^(3),比表面积高达208.05m^(2)/g,导热系数为0.028W/(m·K),热分解温度达560℃。该研究结果可为基于冷冻干燥法的对位芳纶气凝胶孔结构调控提供新思路。

In order to overcome the problem of poor thermal insulation caused by easiness to collapse of aerogel skeleton under freeze-drying conditions,dimethyl sulfoxide(DMSO)and tetrabutylammonium fluoride(TBAF)solutions were prepared to dissolve para-aramid fibers.The pore structure of aerogel was regulated by altering the composition of tert-butyl alcohol/water replacement fluid,and para-aramid aerogels with excellent thermal insulation properties were prepared.The apparent morphology,microstructure,thermal stability,and thermal conductivity of the prepared aerogel were then characterized.The results showed that compared with the water exchange liquid,the addition of tert-butyl alcohol can change the growth morphology of ice crystals,making the interior of aerogel present a uniform three-dimensional reticulated pore structure and further improving the collapse of skeleton.With the increase of volume fraction of tert-butyl alcohol in the exchange liquid,the shrinkage rate of aerogel decreased first and then increased,and the thermal conductivity showed the same trend.When the volume fraction of tert-butyl alcohol was 50%,the shrinkage rate of aerogel was the minimum,and the apparent density was 0.021g/cm^(3).The specific surface area was up to 208.05 m^(2)/g,the thermal conductivity coefficient was 0.028W/(m·K),and the thermal decomposition temperature was 560℃.The results of this study can provide a new idea for pore structure regulation of para-aramid aerogel by freeze-drying method.