Using Sodium Polyacrylate to Gel-Spin Lignin/Poly(Vinyl Alcohol) Fiber at High Lignin Content.

Lignin is the world's most naturally abundant aromatic polymer, which makes it a sustainable raw material for engineered polymers and fiber manufacturing. Dry-jet gel-spinning was used to fabricate poly(vinyl alcohol) (PVA) fibers having 30% or more of the lignin biopolymer. To achieve this goal, 0.45 wt.% of aqueous sodium polyacrylate (SPA, at 0.55 wt.% solids) was added to spinning dopes of PVA dissolved in dimethylsulfoxide (DMSO). SPA served to enable the spinning of fibers having high lignin content (i.e., above 30%) while eliminating the aging of as-spun gel fiber prior to elevated temperature drawing. SPA impedes the migration of acetone soluble lignin from the skin of as-spun gel fibers, because SPA is insoluble in acetone, which is also a nonsolvent coagulant for PVA. PVA fibers having 30% lignin exhibited the highest tenacity of 1.3 cN/dtex (centinewton/decitex) and specific modulus 35.7 cN/dtex. The drawn fiber of 70% lignin to PVA, showed tenacity and specific modulus values of 0.94 cN/dtex and 35.3 cN/dtex, respectively. Fourier Transform Infrared (FTIR) spectroscopy showed evidence of hydrogen bonding between lignin and PVA among the drawn fibers. The modification of PVA/lignin dopes with SPA, therefore, allowed for the fabrication of gel-spun biobased fibers without the previously required step of gel aging.

Glucaric acid additives for the antiplasticization of fibers wet spun from cellulose acetate/acetic acid/water.

Cellulose acetate (CA) receives notable attention as an environmentally friendly, biodegradable polymer from renewable, low-cost resources. CA polymers are believed to have a critical role in shaping a greener and more circular textile economy. However, the mechanical properties of CA fibers are among the lowest in terms of its tensile strength, poor wet strength, and low flexural strength. This study investigates the effect of biobased additives for antiplasticizing the mechanical performance and structure of CA fibers. At up to 5 % of CA, glucaric acid (GA) and its monoammonium salt were added to CA fibers. With 1.5 % GA additive, tensile modulus improved by 155%, tensile strength by 55 %, and CA flexibility according to knot to straight fiber tenacity ratios improved by 107 % when compared to neat CA fibers. Based on the results, green small molecule antiplasticizers do exist, but their performance improvements are observed at low percentages of loading.

Recent developments in bio-monitoring via advanced polymer nanocomposite-based wearable strain sensors.

Recent years, an explosive growth of wearable technology has been witnessed. A highly stretchable and sensitive wearable strain sensor which can monitor motions is in great demand in various fields such as healthcare, robotic systems, prosthetics, visual realities, professional sports, entertainments, etc. An ideal strain sensor should be highly stretchable, sensitive, and robust enough for long-term use without degradation in performance. This review focuses on recent advances in polymer nanocomposite based wearable strain sensors. With the merits of highly stretchable polymeric matrix and excellent electrical conductivity of nanomaterials, polymer nanocomposite based strain sensors are successfully developed with superior performance. Unlike conventional strain gauge, new sensing mechanisms include disconnection, crack propagation, and tunneling effects leading to drastically resistance change play an important role. A rational choice of materials selection and structure design are required to achieve high sensitivity and stretchability. Lastly, prospects and challenges are discussed for future polymer nanocomposite based wearable strain sensor and their potential applications.