Development of hydrophobic thermoplastic starch composites

Abstract

This work deals with provision and characterization of the biopolymer-based composites achieved by incorporation of cellulose fibers as the reinforcement within the glycerol plasticized matrix formed by thermoplastic cornstarch biopolymer. The function of starch-based polymers is limited due to poor mechanical properties. However, it is improved with forming a biocomposite of thermoplastic starch (TPS) as matrix and the cellulose fibers (CF) as reinforcement. The surface of cellulose fibers is successfully modified using the air plasma treatment with the aim of improving the matrix/fiber adhesion. The modified fibers are studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The TPS/CF composites are prepared using high friction and hot compression procedure. Tensile test results and SEM images of the fracture surfaces show significant improvement of adhesion between treated cellulose fibers and TPS matrix. In another hand, starch nanoparticles (SNP) were prepared by delivering ethanol as the precipitant into starch-paste solution dropwise. According to the characterization of starch nanoparticles with FTIR, XRD and SEM, amorphous SNP could not be gelatinized in hot water because of the cross-linking. The TPS/SNP films were also prepared using casting process. SEM and atomic force microscopy (AFM) revealed that SNP was dispersed evenly in the starch matrix. As shown in the dynamic mechanical thermal analysis (DMA) and TGA, the introduction of SNP could improve the storage modulus and the glass transition temperature of the prepared films.