纤维素纳米纤维/纳米蒙脱土复合气凝胶制备及其结构与性能

Preparation and properties of cellulose nanofiber/montmorillonite composite aerogels

针对纤维素纳米纤维(CNF)气凝胶易燃、强力低等问题,利用纳米蒙脱土(MMT)共混改性纤维素纳米纤维,基于冷冻干燥的方法制备阻燃隔热的CNF/MMT复合气凝胶。研究了MMT质量分数对CNF/MMT复合气凝胶形貌结构、压缩性能、热稳定性、热导率和阻燃性能的影响。结果表明:MMT的引入使气凝胶具有更加紧密的片层结构,气凝胶力学性能、热稳定性和阻燃性能得到改善;在MMT质量分数为50%时,CNF/MMT复合气凝胶的表观密度最大且仅为0.0168 g/cm^3,应变为10%的应力最大为12.45 kPa,应变为70%的应力最大为77.93 kPa,导热系数最大为0.04 W/(m·K);气凝胶中MMT质量分数不低于42.9%时,复合基气凝胶的极限氧指数得到明显提升。

To enhance the flammability and mechanical strength of cellulose nanofiber(CNF)aerogels,nanoscale montmorillonite(MMT)were introduced to CNF suspension,followed by a freeze-drying process to obtain CNF/MMT composite aerogels in this work.The effects of MMT content on the morphology characterization,compressive mechanical properties,thermal stability,thermal conductivity and flame retardancy of CNF/MMT composite aerogels were studied.The results show that the presence of MMT resulted in a denser lamellar structure of aerogels,which improved the mechanical properties,thermal stability and flame retardancy of aerogels.When the mass fraction of MMT is 50%,it is found that the CNF/MMT composite aerogels reaches the maximum density but only as low as 0.0168 g/cm^3,that the maximum stress becomes 12.45 kPa at 10%strain and 77.93 kPa at 70%strain,and that the maximum thermal conductivity is 0.04 W/(m·K).The limiting oxygen index values of CNF/MMT based aerogels shows significant increase when the mass fraction of MMT in aerogels is no less than 42.9%.