Heterogeneous Acetylation of Plant Fibers into Micro-
and Nanocelluloses for the Synthesis of Highly Stretchable, Tough,
and Water-Resistant Co-continuous Filaments via Wet-Spinning
posted on 2018-11-28, 00:00authored byAnurodh Tripathi, Mariko Ago, Saad A. Khan, Orlando J. Rojas
Heterogeneous
acetylation of wood fibers is proposed for weakening their interfibrillar
hydrogen bonding, which facilitates their processing into micro- and
nanocelluloses that can be further used to synthesize filaments via
wet-spinning. The structural (SEM, WAXD), molecular (SEC), and chemical
(FTIR, titration) properties of the system are used to propose the
associated reaction mechanism. Unlike the homogeneous acetylation,
this method does not alter the main morphological features of cellulose
fibrils. Thus, we show for the first time, the exploitation of synergies
of compositions simultaneously comprising dissolved cellulose esters
and suspended cellulose micro- and nanofibrils. Such colloidal suspension
forms a co-continuous assembly with a matrix that interacts strongly
with the micro- and nanofibrils in the dispersed phase. This facilitates
uninterrupted and defect-free wet-spinning. Upon contact with an antisolvent
(water), filaments are easily formed and display a set of properties
that set them apart from those reported so far for nanocelluloses:
a remarkable stretchability (30% strain) and ultrahigh toughness (33
MJ/m3), both surpassing the values of all reported nanocellulose-based
filaments. All the while, they also exhibit competitive stiffness
and strength (6 GPa and 143 MPa, respectively). Most remarkably, they
retain 90% of these properties after long-term immersion in water,
solving the main challenge of the lack of wet strength that is otherwise
observed for filaments synthesized from nanocelluloses.