Wet Spinning of Sustainable Hydroxypropyl Cellulose Fibers

Hydroxypropyl cellulose (HPC) is a biobased, biodegradable, and water-soluble material that is used as an emulsifier, thickener, and stabilizer in aqueous formulations. Its solid-state properties render HPC also attractive for water-soluble sanitary products, packaging, and biomedical applications. While HPC films and coatings are well-known, HPC fibers have hardly been investigated, arguably, due to the lack of methods to spin HPC fibers. Here, we show that fibers can readily be produced by wet spinning aqueous HPC solutions into an aqueous CaCl₂ coagulation bath. This process induces significant alignment of HPC chains under shear forces, resulting in fibers with considerably higher stiffness (Young's modulus = 1.3 GPa) and tensile strength (36 MPa) than solution-cast HPC films (Young's modulus = 0.7 GPa, tensile strength = 19 MPa). The HPC fibers retain their mechanical integrity upon conditioning at 60% relative humidity, although stiffness is considerably reduced. Wet spinning is readily scalable and affords stiff and strong fibers that represent a promising alternative to woven and nonwoven synthetic fibers.