Mechanical Fibrillation Capability of Kraft Pulp for Obtaining Cellulose Nanofibers

概要

Cellulose nanofibers (CNFs), which exist in the plant cell wall, are packed densely with the
hemicellulose and lignin matrix to support the mechanical strength of the plant growth.
Due to CNF's structural characteristics, it owns excellent features of mechanical strength,
lightweight, high specific surface area, and low coefficient of thermal expansion. These
outstanding features made CNFs potential raw materials in various areas and were
appealing to use as reinforcement in nanocomposites. The CNF fabrication is processed by
chemical and mechanical methods, including isolating cellulose from raw material and
disintegration cellulose into nanoscale fibers, CNFs. In order to upscale and promote the
practical usage of CNFs, cost-effective and efficient methods are needed.
In order to obtain high aspect ratio fibers that induce greater mechanical strength, the
mechanical disintegration methods were focused for interest. In previous studies, the dried
commercial pulp could be disintegrated with a grinder and homogenizer with extensive
energy input. Later, it was reported that uniform CNFs could easily be obtained from the
never-dried pulp with one grinder treatment pass. The easiness in mechanical fibrillation
of pulps was thought to be attributed to the never-dried pulps in yet hornified and yet
formed irreversible hydrogen bonds during the drying process; hence the pulp could be
easily disintegrated. However, it was found that the disintegration of commercial pulp is
hard to process with excessive mechanical treatment, even in its never-dried state. It was
then considered that if it was the manufacturing process of the raw material pulp for making
cellulose nanofibers affects the nanofibrillation process. Therefore, the motivation of the
current study is to understand whether the pulp-making process influences never-dried
pulp fibrillation.
To identify the issue of why the never-dried state pulp is still hard to fibrillate into uniform
CNFs, (1) the most common pulp-making process, kraft cooking, was used as the method
for preparing the never-dried pulp, (2) the study hopes to find out the key to prepared pulp
that is suitable to prepared CNFs with ease. Kraft cooking was chosen as the study object
since it is the world's dominant pulping method, and its uptake is the most abundant pulp
raw material, kraft pulp. This study aims to optimize kraft cooking for fabricating neverdried pulp, which is feasible for mechanical fibrillation at ease. ...