Chemical recycling of hemp waste textiles via the ionic liquid based dry-jet-wet spinning technology

Abstract

The chemical recycling of hemp fabric into high-tenacity man-made cellulose fibers was demonstrated. The fabric was laundered 25 and 50 times to mimic the wear cycles of post-consumer textile waste. Despite the launderings, the molar mass of the material was still too high for recycling via dry-jet-wet spinning. Thus, the fabrics were treated with an aqueous sulfuric acid solution to adjust the intrinsic viscosity to the targeted level of 400–500 ml/g. The acid hydrolyzed sample was dissolved in 1,5-diazabicyclo[4.3.0]non-5-enium acetate and man-made cellulose fibers were regenerated by dry-jet-wet spinning. The properties of hemp and regenerated fibers were determined by tensile testing, birefringence measurements, and X-ray diffraction. Regenerated fibers were spun into yarn and knitted into a fabric. The tensile properties of the yarn and the abrasion and pilling resistance of the fabric were determined. Regenerated fibers showed a higher modulus of toughness (55.9 MPa) compared with hemp fibers (28.7 MPa). The fineness and staple length uniformity of regenerated fibers resulted in a high yarn structure evenness, a yarn tenacity of 28.1 cN/tex, and an elongation at break of 7.5%. Due to the even fabric structure, the fabric from regenerated fibers showed higher abrasion resistance than the hemp fabric.

High-Quality Cellulosic Fibers Engineered from Cotton–Elastane Textile Waste

“…Figure b shows the influence of the DR on the elongation and tenacity of conditioned and wet fibers. The tenacity values were in the range of previously reported Ioncell cellulosic fibers and surpass most commercial MMCFs currently on the market . Moderate elongation was also observed earlier when using waste cotton as a cellulose substrate. , The increase in elongation and decrease in strength under wet conditions are characteristic of MMCFs and are due to the swelling of amorphous domains.…”

“…This difference can be explained by the relatively high molecular weight of the cellulose even after acid hydrolysis ([η] COR = 581 mL·g –1 ). This value is close to the upper limit for dopes with good spinnability . Fibers were regenerated by dry-jet wet spinning.…”

“…The spinning dope was prepared via the dissolution of the treated cellulose in [DBNH]­[OAc], and the rheological properties of the dope were measured to identify suitable spinning conditions. A zero shear viscosity (η 0 * ) close to 30 000 Pa·s, a crossover point (COP) at around 1 s –1 , and a modulus between 4000 and 5000 Pa were found to be suitable for cellulose (13% eucalyptus pulp) spinning in [DBNH]­[OAc] . In the case of the prepared dope, no COP was observed within the frequency range measured (Figure S5).…”

“…The regenerated fibers often exceed the properties of the initial materials. 5,6 Chemical recycling becomes a challenge when textile blends are involved. Polyester and elastane are examples of synthetic fibers commonly blended with cellulose.…”

“…This technique enables fiber-to-fiber recycling by the conversion of textile waste into second-generation fibers of high quality. The regenerated fibers often exceed the properties of the initial materials. , …”