冻干保护剂对纤维素纳米纤维气凝胶的影响

Application of Cryoprotectant in Cellulose Nanofibers Aerogels

关键词:  纤维素纳米纤维；气凝胶；冻干保护剂；山梨醇  甘露醇  蔗糖

Key Words:cellulose nanofibers  aerogels  cryoprotectant  sorbitol  sucrose  mannitol

摘要:以漂白针叶木浆为原料，通过TEMPO氧化法制得纤维素纳米纤维（CNF），再经冷冻干燥制得低密度、高比表面积及高压缩强度的CNF气凝胶。针对CNF气凝胶强度较低并且孔径分布不均的问题，本研究采用在CNF悬浮液中加入不同种类的冻干保护剂（山梨醇、甘露醇及蔗糖）的方法，达到缩小气凝胶孔隙结构，增强气凝胶压缩强度的效果。使用透射电子显微镜（TEM）、扫描电子显微镜（SEM）、比表面和孔径分布分析仪、X射线衍射仪（XRD）、红外光谱仪(FT-IR)和热重分析仪(TG)等对其结构及性能进行表征。结果表明，加入冻干保护剂（山梨醇、甘露醇及蔗糖）后，制得的CNF气凝胶尺寸均一，直径为10～20 nm；气凝胶孔隙分布趋于均匀，压缩强度显著提高。此外，冻干保护剂的加入不会对CNF气凝胶的晶型结构及热稳定性产生影响。

Abstract:Bleached softwood kraft pulp was used as the raw material for the preparation of cellulose nanofibers （CNF） by TEMPO-mediated oxidation method， and CNF was converted to the low density， high-specific surface and high-strength aerogels after freeze-drying. But the CNF aerogels has low strength and non-uniform pore size. In order to improve the strength of aerogels， different kinds of cryoprotectants including sorbitol， sucrose and mannitol were added to the CNF suspension to reduce the pore structure and create uniform distribution of the pore size. The structures and properties of CNF aerogels were characterized by TEM， SEM， BET， XRD， FT-IR and TGA. The results showed that the CNF had homogeneous size and its diameter was 10～20 nm， and the pore size distribution of aerogels tended to be uniform after cryoprotectant was added. Additionally， the mechanical strength of CNF aerogels was greatly improved by the addition of cryoprotectant， and it would not affect the crystal structure and thermal stability of aerogels.