Green Preparation of Thermochromic Starch-Based Fibers through a Wet-Spinning Process

A starch-graft-poly(butyl acrylate/styrene) (St-g-PBAS) copolymer was synthesized via grafting butyl acrylate (BA) and styrene (S) monomers onto starch by radical polymerization, and ammonium persulfate (APS) was used as an initiator. Thermochromic St-g-PBAS fibers with a full core structure were achieved through a wet-spinning process via coagulating a dope-dyed St-g-PBAS/dimethylacetamide (DMAc) solution in water. The effects of spinning conditions such as temperature and the drawing rate in a coagulation bath, drawing and stretching multiples of the primary fiber in hot water, thermal setting temperature, and time on the finished fiber mechanical performances were examined. The St-g-PBAS copolymer was analyzed by Fourier transform infrared spectra (FT-IR), solid-state nuclear magnetic resonance (13C NMR), thermal gravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS). The fiber performances were characterized by a scanning electron microscope (SEM), X-ray diffraction (XRD), and a fiber mechanical determinator. The results showed that the substitution degree of starch was 0.51, and the obtained St-g-PBAS fiber had the full core structure and excellent mechanical performances with high breaking strength (up to 2.11 cN·dtex–1), thermal stability, and elasticity (breaking elongation of up to 88.2%). The fiber color changes repeatedly between purple and pink as the temperature increases and then decreases to 31 °C.