Thermal and Tensile Properties of PP Nanocomposite Blends
Polypropylene/polyamide-6 and polypropylene/metallocene polyethylene blends containing 2.5 phr of organophilic modified montmorillonite were prepared in a twin-screw extruder followed by injection molding. In order to compare, blends without layered clay were also made. Styreneethylene- butylene-styrene copolymer and polypropylene grafted with anhydride maleic were used as compatibilizers in the ternary blends and in the PP nanocomposite preparation, respectively. The presence of tactoids, intercalated and exfoliated structures was observed by TEM in some of the samples containing layered clay and modified PP materials. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant changes in tensile moduli were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene exhibited better tensile toughness and lower tensile modulus, than those prepared with a nanocomposite of PP and polyamide-6 as dispersed phase. These results are related to the degree of clay dispersion in the PP and to the type of morphology developed in the different blends. Differential scanning calorimetry (DSC) showed that blends with a finer and homogeneously dispersed morphology determined by SEM, the PA component exhibited fractionated crystallization exotherms in the temperature range of 159-185°C. Also, nucleation of the PP component by PA phase and/or the layered clay was observed in the blends with PA as dispersed phase.
Prof. Alan Kin Tak Lau, Dr. J. Lu, Vijay K. Varadan, Fu-Kuo Chang, J.P. Tu and Pou Man Lam
C. Rosales et al., "Thermal and Tensile Properties of PP Nanocomposite Blends", Advanced Materials Research, Vols. 47-50, pp. 21-24, 2008