Abstract

Plant fiber isolated cellulose nanofibers (CNFs) are the materials with excellent mechanical properties. However, application of CNFs in polymer reinforcement is normally unsatisfactory due to its intertwined size distribution. Efforts to produce uniform sized CNFs have yet to be studied. In present work, spiral microchannel was used to fractionate CNFs based on the balance between inertial lift force (F_L) and Dean drag force (F_D) exerted on CNFs. The results showed that the smaller length of CNFs equilibrated near the inner microchannel while the larger length of CNFs occupied the equilibrium position away from the inner wall. With the increase of flowrates from 50 to 220 μL/min, fractionation efficiency between inner and middle outlet (E_IM) of spiral microchannel A with larger radius curvature (R) from 5 to 15 mm increased from 0 to 75.4%. However, stronger Dean flow attributing to decrease of R (3 mm to 10 mm) of single spiral microchannel B enabled satisfactory fractionation efficiency of 70.9% at flowrate of 90 μL/min. Moreover, the fractionation efficiency of double spiral microchannel with twice as length as microchannel A and three times as length as microchannel B was lower than that of single spiral microchannel at flowrate lower than 90 μL/min. Furthermore, this study exhibited a versatile and simple method for CNFs fractionation with high fractionation efficiency.

Graphic abstract

摘要

植物纤维分离的纤维素纳米纤维（CNFs）是具有优异机械性能的材料。但是，由于CNF交织在一起的尺寸分布，通常不能令人满意。生产均匀大小的CNF的努力尚待研究。在目前的工作中，基于惯性升力（F _L）和施加在CNF上的Dean拖曳力（F _D）之间的平衡，使用螺旋微通道对CNF进行分级。结果表明，较短的CNF长度在内部微通道附近平衡，而较大的CNF远离内壁占据平衡位置。随着流量从50μL/ min增加到220μL/ min，内部和中间出口之间的分馏效率（E _IM较大的半径曲率（R）从5到15毫米的螺旋微通道A的）从0增至75.4％。然而，归因于单个螺旋微通道B的R（3mm至10mm）减小的更强Dean流量在流量为90μL/ min时实现了令人满意的70.9％的分馏效率。此外，在流速低于90μL/ min的情况下，具有两倍于微通道A的长度和两倍于微通道B的长度的双螺旋微通道的分馏效率低于单螺旋微通道。此外，本研究展示了一种具有高分离效率的通用且简单的CNF分离方法。

图形摘要