Alkali-soluble polyethylene terephthalate/calcium alginate composite fibers: better mechanical and dyeing properties

Calcium alginate fiber (CAF) is a bio-based material recognized for its excellent biocompatibility, degradability, and inherent self-flame retardancy, making it a promising candidate for various applications. However, its mechanical and dyeing properties often fall short of expectations. In this work, we produced composite fibers through wet spinning techniques by combining alkali-soluble polyethylene terephthalate (COPET) and sodium alginate (SA). The incorporation of COPET enhanced the stability of the co-spinning solution. The increased rigidity of COPET molecules, with their entanglement and hydrogen bonding with SA molecules, resulted in improved viscosity and modulus in the co-spinning solution, demonstrating a more pronounced shear-thinning behavior. Moreover, the mechanical properties of the composite fibers show a significant improvement, achieving a strength of 5.77 ± 0.48 cN/dtex, representing a 124 % improvement over pure CAF. These composite fibers retained the excellent flame-retardant qualities of CAF (LOI = 35.1 %) while substantially addressing the smoldering. Additionally, attributed to the -SO₃ in COPET, the composite fibers exhibited enhanced dyeing properties, achieving 87.62 % dye exhaustion, with a dry rubbing grade elevated to Grade 4 and a wet rubbing grade to Grade 3-4. This research offered a new approach to improving the mechanical and dyeing properties of CAF.