Oxidation and cross-linking to improve stability and sizing properties of cassava starch with ammonium persulfate-assisted hexamethylenetetramine

Abstract

An oxidation cross-linking modified cassava starch (AHS-U) with high-viscosity stability and good film-forming properties was synthesized by oxidation cross-linking reaction, which used ammonium persulfate (APS) as the oxidant, hexamethylenetetramine (HMT) as the cross-linking agent and urea as an assistant. The results of Fourier transform infrared spectroscopy and nuclear magnetic resonance showed that compared with cassava starch, APS oxidized starch exhibited carboxyl characteristic peaks in its structure, and the hydroxyl proton peak that was connected at the C6 position basically disappeared in the APS-HMT modified cassava starch (AHS). The cross-linking agent HMT released formaldehyde under heating conditions to cross-link oxidized starch. The urea formed hydrogen bonds with hydroxyl groups in the starch while adsorbing residual formaldehyde, which improved the viscosity stability of the sizing agent. When the APS dosage was 0.4% (the carboxyl content was 0.30%), the HMT dosage was 0.35% (the sedimentation volume was 7.8 mL) and the urea dosage was 2%, the viscosity stability of the AHS-U sizing agent was good under high-temperature conditions (97.12%), and the elongation of the sizing film reached 2.97%. The AHS-U sizing agent can improve the tensile properties and wear resistance of cotton yarn and has a good desizing efficiency. This study overcomes the toxic substance emissions caused by traditional aldehyde cross-linking agents, improves the viscosity stability of the starch sizing agent and provides a new approach to improving the viscosity stability and film-forming properties of starch sizing agents.