Chemically Modified Konjac Glucomannan Nanocrystal And Its Effects On Polyurethane

Traditional inorganic nano-fillers, the important reinforcing fillers used mostly today, are undegradable as well as harmful to human body and the environment. Natural organic nanocrystals obtained from polysaccharides such as starch, cellulose and chition not only inherit all the advantages of natural polymes, but also show a reinforcing function in composites by virtue of their rigidity similar to those traditional inorganic nano-fillers. Konjac is the local resource of China, as a kind of renewable polymer, which has the potential to substitute for the inorganic nano-fillers as the reinforcing particles.The main research contents and conclusions in this thesis are as follows:1. The KGM nanocrystals were obtained by acid hydrolysis of Konjac, and then the surface chemical modification of KGM nanocrystals was preformed using the benzoyl chloride in order to lower the nanoparticals'surface energy so that they could disperse well in organic solvent. The FTIR spectroscopy confirmed the successful chemical modification of KGM nanocrystals with benzoyl chloride. X-ray diffraction measurement proved the surface chemical modification did not alter the crystallinity of KGM nanocrystals. The contact anlge measurements and the wetting practise proved the modification lowered the surface energy successfully. The TEM showed that the KGM nanocrystals after modification had the platelet shape like the unmodified KGM nanocrystals.2. A serials polyurethane/KGM nanocrystals nanocomposites were obtained by casting the composites on glass plates. The mechanical characterization indicated that the nanoparticals had reinforcing effects on PU when its content was 0.5wt%. At this content, the tensile strengh was 1.37MPa compared to 1.19MPa that of the pure PU. SEM, FTIR and XRD tests showed when the content of KGM was 0.5wt%, the nano-fillers could disperse well in the PU matrix and had strong interaction with the PU matrix.3. A serials polyurethane/modified KGM nanocrystals nanocomposites were obtained by casting the composites on glass plates. SEM, FTIR and XRD tests proved the modified KGM nanocrystals dispersed well in the PU matrix and the interaction between the fillers and the matrix were quite strong. With the increasing content of KGM nanoparticals, the tensile strengh and the breaking elongaiton were both increasing. When the content of KGM was 2.0wt%, the PU composites had the maximal tensile strenth and breaking elongation. The change indicated the necessity of surface chemical modification of KGM nanocrystals.The results of this research on the modification of natural polymer nanocrystals and the preparation as well as the characterization of composites provided important scientific foundation for the further development and application of natural nanoparticals. Therefore, this study has theoretical significance and application prospect, which is well consistent with the target of environmental protection and the strategy of sustainable development.