Effects of lactic acid and mixed acid aqueous solutions on the preparation, structure and properties of thermoplastic chitosan

Abstract In this paper, a lactic acid (LA) aqueous solution and a mixed acid (MA) aqueous solution, composed of lactic acid and hydrochloric acid (HCl), were used as plasticizers to plasticize thermoplastic chitosan. The plasticizing behavior of chit-osan under melt processing with different concentrations of the LA and MA solutions and different ratios of HCl and LA were studied. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) indicated that the acidity and concentration of the ac-id solution had direct impacts on the chitosan structure. The thermal melting effect o-f chitosan was improved with increasing lactic acid concentration in the LA solutio-n and HCl concentration in MA solution. The sheet light transmission, hydrophobicit-y, thermal stability and mechanical properties of thermoplastic chitosan could be adj-usted by changing the ratios of hydrochloric acid and lactic acid in the MA solutio-n. This work expanded the theoretical knowledge of acid solution modified thermopla-stic chitosan.