The Influence of the Multi-level Structure Under High Drawing on the Preparation of High Strength Lyocell Fiber

Abstract

In order to research the multi-level structure of Lyocell fiber at different draw ratios and to reveal the limiting factors for preparing the high strength Lyocell fiber, the paper reports on the effect of draw ratio including low drawing (1–5), high drawing (6–11) and excessive drawing (12–20) on the multi-level structure and the mechanical properties of Lyocell fiber. The structure was determined by wide-angle X-ray diffraction, small-angle X-ray scattering and fibrillation test, and the result showed that, at low draw ratio stage, the breaking strength, yield strength and modulus of the fiber increased with the draw ratio owing to crystallinity as well as orientation increased while the micropore decreased, and there are almost no microfibrils on the fiber surface. At high draw ratio stage, the orientation of amorphous region increasing was the principal reason for the increase of fiber mechanical properties, and the micropores continued to decrease and a few short and thick microfibril was formed. At excessive draw ratio stage, the breaking strength remained constant mainly due to the basically unchanged crystallinity and orientation of the fibers, the yield strength and modulus decreased due to the slip of the highly crystallized and oriented elementary fibril. Meanwhile, the micropores still decreased and became much slenderer, the number of microfibrils increased and the microfibrils showed tenuous structure. It could be summarized that Lyocell fiber had the characteristics of multi-level structure, and the fundamental reason limiting the improvement of mechanical properties with draw ratio increase was the slip of elementary fibril.

The influence of pulp swelling degree during pre-mixing on the stability of Lyocell solution

“…Shiqiang (2022) observed that direct cellulose dissolution using NMMO 87% produces worse lyocell dope quality compared to the indirect dissolution using NMMO 50% followed by water evaporation. Other studies also found that even the direct method can dissolve cellulose at a high rate but insufficient hydrogen bonding between cellulose and NMMO, thus can't satisfy good swelling and lead to unwanted heterogeneous solution [6], [31].…”

Biomanufactured High-Performance Triboelectric Fibers for Respirators

“…3d), which is expected with drawn fibers. Drawing induces constituent fibrils to align along the fiber axis, contributing to fiber strength 18 . Several allomorphs of cellulose and cellulose triacetate have been reported, and we observed cellulose-II and cellulose triacetate-II in the WAXS spectra 19,20 .…”