The utilization of cellulose and chitin nanoparticles in biodegradable and/or biobased thermoplastic nanocomposites.

摘要

This dissertation describes the isolation, characterization, derivatization, and application of chitin and cellulose nanoparticles in composite materials. Chitin and cellulose both serve a natural role as structural reinforcing elements in the organisms in which they reside. Chitin and cellulose nanoparticles were isolated from shrimp shells, and bacterial cellulose, respectively using processes of acid hydrolysis and mechanical dispersion. Both types of polysaccharide nanoparticles were obtained with high purity and crystallinity. The specific surface areas of these particles, measured by adsorption of Congo red dye, ranged from 250 m2/g to 350 m2/g depending upon the source material. The chitin nanoparticles were topochemically modified with medium to long-chain esters in a heterogeneous reaction system to improve their compatibility with a matrix plastic, for composite applications. A long-chain cellulose ester thermoplastic matrix was reinforced with the modified chitin nanoparticles. The roles of surface modification and substituent chain length on particle-matrix compatibility expressed through the thermal and mechanical properties of the composites were studied. Large increases in tensile storage modulus were observed for the reinforced materials. Additionally, 2 to 3-fold improvements in modulus were achieved through topochemical modification of the particulate phase. Similarly, for cellulose nanoparticles, epsilon-caprolactone oligomers were chemically grafted to the surface via ringopening polymerization. These particles were melt processed with a poly (epsilon-caprolactone), (PCL), matrix. The thermal and mechanical properties were also improved as a result of reinforcement. The mechanical performance properties of both the chitin and cellulose nanocomposites were referenced against those of similarly prepared nanoclay composites. In all cases our materials matched or exceeded the performance of these reference materials. Finally, the biodegradation of the prepared nanocomposites was assessed in a compost medium. Both particle and matrix phases of the PCL composites were biodegradable, while that of the longchain cellulose ester was not. The process from nanoparticle isolation to nanocomposite degradation is discussed.; Keywords. chitin nanoparticles, cellulose nanoparticles, mechanical dispersion, topochemical modification, nanocomposites, tensile storage modulus, melt processing, biodegradation