Thesis (M.Sc.)--Chulalongkorn University, 2008

This research investigated the beta nucleation of polypropylene (PP)/montmorillonite composites via melt compounding in a co-rotating twin-screw extruder. Polypropylene (PP) and polypropylene/polypropylene-g-maleic anhydride/montmorillonite clay (PP/PP-g-MA/montmorillonite clay) composites were modified with 0.05, 0.10 and 0.30 wt% aryl amide nucleator (beta-nucleator) to promote the formation of the hexagonal (beta) crystal modification during melt crystallization. The non-isothermal crystallization behavior of PP, PP/PP-g-MA/montmorillonite composites and beta-nucleated PP/PP-g-MA/montmorillonite composites was studied by means of differential scanning calorimetry (DSC). The structure-property relationships of PP-composites prepared by melt processing have been investigated with the main focus on the quantity of aryl amide. The morphological and crystal structure observations obtained from scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) were discussed in conjunction with the mechanical, rheological and thermal properties of these composites. The chemical interaction in composites was observed by FTIR. The PP/PP-g-MA/montmorillonite clay composites modified with 0.05, 0.10 and 0.30 wt% aryl amide nucleator promoted growth of the hexagonal (beta) crystal with the values of 0.50, 0.92 and 0.92, respectively. The beta-crystal modification was found to increase thermal and mechanical properties of the PP and PP-composites, whereas the nanoclay dramatically increased stiffness and impact of the composites, the loss of tensile elongation was found to be partially compensated by aryl amide. The effect on increasing density by the clay compound was reduced via the beta-nucleation of aryl amide. The most important finding of aryl amide nucleation of PP/PP-g-MA/montmorillonite clay composites was the dramatic increase in crystallization temperature of the PP/PP-g-MA/organoclay/aryl amide by 12 °C.