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 chitosan 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 acid solution had direct impacts on the chitosan structure. The thermal melting effect of chitosan was improved with increasing lactic acid concentration in the LA solution and HCl concentration in MA solution. The sheet light transmission, hydrophobicity, thermal stability and mechanical properties of thermoplastic chitosan could be adjusted by changing the ratios of hydrochloric acid and lactic acid in the MA solution. This work expanded the theoretical knowledge of acid solution modified thermoplastic chitosan.