纤维素纳米晶体形态尺寸的流变学表征及其悬浮液复杂流变行为的研究

Cellulose Nano-crystal (CNC) is a rod shaped nanoscale material, which has been isolated from cellulose fibers. Due to the advantages of CNCs’ high modulus, low density, high aspect ratio, and negligible thermal expansion, CNCs have been widely used in polymer reinforcement and functional materials. Aspect ratio is an important parameter of CNC which decides the properties of CNC materials. Nowadays, microscopy observation and statistics is the conventional method for CNC aspect ratio characterizing, which is intuitive but has disadvantages such as large statistical work, long measurement period, and randomness of CNC aspect ratio results. According to the kinetics function of rigid rod, rheological measurement can be used to characterize CNC aspect ratio. However, to our knowledge, no papers have reported CNC aspect ratio characterization by rheolgical measurement. Therefore, the main objective of this proposal is to study the relationship between CNC aspect ratio and the rheological behavior of its suspension, and provide theoretical basis and operation program for CNC aspect ratio characterization by rheology measurement. The specific objectives included two parts, first, studying the influence of electrostatic repulsion effect on the kinetics and rheological behavior of sulfuric acid hydrolysis CNC suspension, and modifying the current kinetics function to describe CNC aspect ratio; second, searching for the optimum condition to obtain electrostatic screened or stable CNC dispersion by adding salt or surfactant, then using the current kinetics function to characterize CNC aspect ratio.

纤维素纳米晶体（Cellulose Nano-Crystal, CNC）是从纤维素中提取的一种直径纳米级的棒状晶体，在纳米增强材料与功能材料领域有重要应用价值。长径比为CNC最重要的性能指标，目前主要通过显微观察统计法表征，该方法直观可见，但存在测量工作量大、周期长、统计数据有随机性等不足。根据刚性棒动力学方程，流变法可作为表征CNC长径比的一种简单有效手段，但是，目前该领域的研究几乎空白。本申请拟开展CNC形态尺寸与其悬浮液流变行为构效关系的研究，通过考察CNC悬浮液的流变与扩散行为随CNC长径比、CNC表面电荷密度、外加盐、表面活性剂的变化规律，揭示静电排斥作用对CNC动力学行为的影响规律；探寻添加盐或表面活性剂获得静电屏蔽或稳定分散CNC悬浮液的最佳条件，为用流变法有效表征CNC长径比提供理论依据和可行的操作方案，并为CNC悬浮液复杂流变行为和稳定性研究积累一定的经验和提供必要的借鉴。

纳米纤维素因其可再生、高强度等因素成为目前研究的热点，但其形态的表征目前仍采用电镜观察统计的方法，该方法直观精确，但是设备昂贵，耗时耗力，不适合在工业生产中使用。本项目主要研究了纤维素纳米晶体（CNC）悬浮液的流变行为，系统考察了外加盐种类、浓度、CNC表面电荷密度及CNC形态分布等因素对CNC悬浮液流变行为和特性粘数([η])的影响，构建了CNC表面电荷密度与其悬浮液[η]的定量关系，发现了准确估算CNC长径比的最佳条件，建立一套用流变方法有效表征CNC长径比的实施方案，并证实了用流变学方法表征CNC长径比的可靠性。流变法可以作为替代TEM和AFM的一种经济、快速和准确的表征CNC形态的方法，特别适合在工业生产中使用，具有重要的应用前景。