Qin Yanlin, Qiu Xueqing, Zhu J Y
School of Chemical Eng. and Light Industry, Guangdong Univ. Technol., Guangzhou, China.
USDA Forest Service, Forest Products Lab., Madison, WI, USA.
Sci Rep. 2016 Oct 31;6:35602. doi: 10.1038/srep35602.
Here we used dilute oxalic acid to pretreat a kraft bleached Eucalyptus pulp (BEP) fibers to facilitate mechanical fibrillation in producing cellulose nanofibrils using disk milling with substantial mechanical energy savings. We successfully applied a reaction kinetics based combined hydrolysis factor (CHF) as a severity factor to quantitatively control xylan dissolution and BEP fibril deploymerization. More importantly, we were able to accurately predict the degree of polymerization (DP) of disk-milled fibrils using CHF and milling time or milling energy consumption. Experimentally determined ratio of fibril DP and number mean fibril height (diameter d), DP/d, an aspect ratio measurer, were independent of the processing conditions. Therefore, we hypothesize that cellulose have a longitudinal hierarchical structure as in the lateral direction. Acid hydrolysis and milling did not substantially cut the "natural" chain length of cellulose fibrils. This cellulose longitudinal hierarchical model provides support for using weak acid hydrolysis in the production of cellulose nanofibrils with substantially reduced energy input without negatively affecting fibril mechanical strength.
在此，我们使用稀草酸对硫酸盐法漂白桉木浆（BEP）纤维进行预处理，以便在采用盘磨生产纤维素纳米纤丝时促进机械原纤化，同时大幅节省机械能。我们成功应用基于反应动力学的组合水解因子（CHF）作为强度因子，以定量控制木聚糖溶解和BEP原纤解聚。更重要的是，我们能够使用CHF以及研磨时间或研磨能量消耗准确预测盘磨原纤的聚合度（DP）。实验测定的原纤DP与数均原纤高度（直径d）之比DP/d，即一个长径比测量值，与加工条件无关。因此，我们推测纤维素在纵向具有与横向类似的层级结构。酸水解和研磨并未大幅切断纤维素原纤的“天然”链长。这种纤维素纵向层级模型为在生产纤维素纳米纤丝时使用弱酸水解提供了支持——在大幅降低能量输入的情况下，不会对原纤机械强度产生负面影响。
