High-Performance Gel-Spun Poly(vinyl alcohol) Fibers Reinforced by Organosolv Lignin-graft-poly(acrylic acid)

Abstract

Water-soluble synthetic poly­(vinyl alcohol) (PVA) polymers can be used as a raw material for high-performance solution-spun fibers. To enhance the biodegradability and physical properties of PVA fibers, lignin has been considered a low-cost, biobased filler/additive for PVA fibers. However, its amorphous structure and hydrophobic nature cause difficulty in developing lignin-reinforced PVA high-performance fibers due to the poor compatibility of amorphous lignin and linear semicrystalline hydrophilic PVA. Herein, the graft copolymerization of organosolv lignin (OL) and acrylic acid (AA) was performed at different reaction durations to yield hydrophilic lignin copolymers, which had enhanced compatibility with polar synthetic PVA. Chemically modified OL with reaction durations of 0, 12, and 24 h was incorporated into PVA fibers by gel spinning. With 5% modified OL from 24 h of reaction time, the composite fibers had an excellent tensile strength of 1.15 GPa, which was 61.4% higher than that of neat PVA fibers. This fiber’s Young’s modulus (13.09 GPa) and toughness (26 J/g) were also substantially enhanced when compared with those of the neat PVA fibers (Young’s modulus of 8.97 GPa and toughness of 18.09 J/g). This work enables the high-value utilization of a modified lignin filler in synthetic fibers for potential applications in industrial or technical textile fields.

Insight into the structure and mechanical performance of high content lignin reinforced poly (vinyl alcohol) gel‐spun fibers via the regulation of esterified hydrophilic lignin composition for better sustainability

“…In this work, F3 possesses tensile strength of 1096 ± 24 MPa and Young's modulus of 28 ± 2 GPa, respectively. These values are significantly higher than those of reported neat PVA fibers 14,18 (tensile strength of 715-930 MPa, Young's modulus of 9-20 GPa). Moreover, the fiber mechanical performance in this work is considerably superior to other reported high lignin content solution-spun composite fibers, which include 53/47 (w/w) polyacrylonitrile/lignosulfonate (PAN/LS) F I G U R E 1 (a) Representative stress-strain curves, and mechanical properties including (b) tensile strength, Young's modulus, (c) toughness and elongation at break of F1, F2, F3, F4, and F5.…”

“…To better illustrate the effectiveness of high content lignin mixture in improving the physical properties of gel-spun PVA fibers, the mechanical properties of F3 and high-performance fibers from the literature 14,18,[22][23][24] are summarized in Figure 1d. In this work, F3 possesses tensile strength of 1096 ± 24 MPa and Young's modulus of 28 ± 2 GPa, respectively.…”

“…Moreover, the fiber mechanical performance in this work is considerably superior to other reported high lignin content solution-spun composite fibers, which include 53/47 (w/w) polyacrylonitrile/lignosulfonate (PAN/LS) F I G U R E 1 (a) Representative stress-strain curves, and mechanical properties including (b) tensile strength, Young's modulus, (c) toughness and elongation at break of F1, F2, F3, F4, and F5. (d) Comparison of the mechanical performance of F3 in this work with neat PVA fiber, 14,18 53/47 (w/w) PAN/LS fiber, 22 1/0.25 (w/w) PAN/lignin fiber 23 and 2/1(w/w) PAN/lignin fiber 24 from the literature. [Color figure can be viewed at wileyonlinelibrary.com] fiber 22 (tensile strength of 15.45 ± 0.74 MPa, Young's modulus of 0.72 ± 0.04 GPa), 1/0.25 (w/w) PAN/lignin fiber 23 (tensile strength of 142 ± 8 MPa, Young's modulus of 10 ± 0.4 GPa) and 2/1(w/w) PAN/lignin fiber 24 (tensile strength of 616.24 ± 19.50 MPa, Young's modulus of 29.89 ± 1.25 GPa), and so forth.…”

“…Although second reinforcement material can serve as a bridge that strengthens the interaction among three compositions within composite fibers, it is hard to identify lignin's contribution to the enhancement of fiber performance at high lignin content in the complex ternary system. Alternatively, chemical modification can be applied to alter the structure of lignin by introducing more hydrophilic groups, thus enhancing its interfacial bonding with polar polymer matrix 14,18 . Modified hydrophilic lignin can be obtained by different methods, such as graft‐copolymerization of OL with acrylic acid 18 or the esterification of OL with D‐gluconic acid, 14 and so forth.…”

“…Alternatively, chemical modification can be applied to alter the structure of lignin by introducing more hydrophilic groups, thus enhancing its interfacial bonding with polar polymer matrix. 14,18 Modified hydrophilic lignin can be obtained by different methods, such as graftcopolymerization of OL with acrylic acid 18 or the esterification of OL with D-gluconic acid, 14 and so forth. For instance, 5 wt% esterified hydrophilic lignin obtained after 48 h of reaction time significantly enhanced the mechanical performance of PVA gel-spun fibers (tensile strength of 1.3 GPa, Young's Modulus of 20.7 GPa) when compared with neat PVA fibers (tensile strength of 0.9 GPa, Young's Modulus of 19.9 GPa).…”