干燥方式对氯化钠预处理后纤维素纳米纤丝再分散性能的影响

Effect of Drying Methods on Redispersion Properties of Cellulose Nanofibril Pretreated with Sodium Chloride

关键词:  纤维素纳米纤丝  真空干燥  冷冻干燥  分散性能

Key Words:cellulose nanofibril  vacuum drying  freeze drying  redispersion

摘要:本研究利用氢键阻滞剂氯化钠对制备的纤维素纳米纤丝（CNF）进行了干燥前预处理，探讨了真空干燥和冷冻干燥两种干燥方式对CNF再分散性能的影响，借助扫描电子显微镜、X射线衍射仪、多重光散射分析仪、流变仪对CNF的性能进行了分析表征。结果表明，真空干燥（55℃）可以促进氯化钠的氢键阻滞作用，采用氯化钠预处理后，真空干燥得到CNF的结晶度为64.7%，相比冷冻干燥（-84℃）处理的CNF的结晶度（66.7%）降低了2个百分点。真空干燥所得CNF水溶液再分散性能较高，真空干燥后水溶液再分散的CNF稳定性指数在0~0.45之间，相比冷冻干燥处理的CNF稳定性指数范围（0~4.5）要小。采用氯化钠预处理有利于提高CNF再分散悬浮液的稳定性，经过氯化钠预处理后真空干燥CNF的表观黏度明显低于经冷冻干燥CNF的表观黏度。

Abstract:In this study， sodium chloride， a hydrogen bond blocker， was used to pretreat cellulose nanofibril （CNF） before drying. The effects of vacuum drying and freeze drying on the redispersibility of CNF were discussed. The properties of CNF were analyzed and characterized by scanning electron microscope， X-ray diffraction， multiple light scattering analyzer and rheometer.The results showed that vacuum drying （55℃） could promote hydrogen bond blocking of sodium chloride （NaCl）. After NaCl pretreatment， the crystallinity of CNF obtained by vacuum drying was 64.7%， which was 2 percentage points lower than that of CNF obtained by freeze drying （-84℃） （66.7%）. The redispersibility of vacuum dried CNF aqueous suspension was higher. The stability index of redispersed CNF after vacuum drying ranged from 0 to 0.45， which was smaller than the range stability index （0 to 4.5） of CNF after freeze drying. Pretreatment with sodium chloride was beneficial to improve the stability of redispersed CNF suspension. The apparent viscosity of vacuum-dried CNF with sodium chloride pretreatment was obviously lower than that of freeze-dried CNF.