Blending caproylated starch with poly(acrylic acid)-g-protein-g-poly(methyl acrylate) as an adhesive material to improve the adhesion of starch to PLA fibers

Abstract Caproylated starch (CS) with different degrees of substitution (DS) and poly(acrylic acid)-g-protein-g-poly(methyl acrylate) (PAA-g-protein-g-PMA) were prepared and then blended as an adhesive material to improve the adhesion of starch to polylactic acid (PLA) fibers for fulfilling the high-valued utilization of feather wastes and enhancing the end-use issue of starch in textile sizing. The CS and PAA-g-protein-g-PMA were characterized by Fourier transform infrared (FT-IR) spectroscopy and proton nuclear magnetic resonance (1H NMR), respectively. The adhesion was evaluated by measuring bonding forces of the blends to PLA fibers. The FT-IR and 1H NMR analyses demonstrated the successful preparations of CS and PAA-g-protein-g-PMA, respectively. The adhesion results showed that the adhesion of CS/PAA-g-protein-g-PMA blends to PLA fibers were superior to that of acid-converted starch (40.6 N), indicating that blending can improve the adhesion of starch to PLA fibers. The adhesion of the blends to PLA fibers was correlated with the DS values of CS samples and blending ratios of PAA-g-protein-g-PMA to CS. With the increase in the DS, bonding force increased, reached its highest value of 53.9 N at DS = 0.027, and then decreased to 52.2 N (DS = 0.033). When the DS value was 0.027, the forces gradually increased from 45.5 to 53.9 N as the ratios were raised from 0 to 7.5 wt%. In brief, the suitable DS value and blending ratios were 0.027 and 5~7.5 wt% for the use of CS/PAA-g-protein-g-PMA blend as an adhesive material in the application of PLA sizing.