Polymer Engineering and Science, Vol.60, No.6, 1301-1315, 2020
Phase-selective micro-structural effects on rheological-networks, segmental relaxation, and electrical conductivity behavior of melt-mixed polyamide-12/polypropylene-multi walled carbon nanotubes ternary nanocomposites
Morphological interpretations and their correlation with biphasic rheological networks and subsequent segmental relaxation, and electrical conductivity were comprehensively addressed for polyamide-12/polypropylene-multi-walled carbon nanotubes (PA-12/PP/MWNT) based ternary nanocomposites fabricated by melt mixing route. The partial migration of MWNT from PP to PA-12 phase is evident from the spreading coefficient estimations based on interfacial dynamics and transmission electron microscopy (TEM) analysis. Melt rheology measurements based on scaling parameters associated with various viscosity models such as, Cross model, Carreau-Yasuda model, and Berzin model indicated systematic variation in network rigidity that is in tune with dispersion-selective nano-morphology of the nanocomposites. The phase inversion was attained for composition in the range of 50 to 60 wt% of PP-MWNT content as indicated by Han plot and van-Gurp Palmen plots which is in direct correspondence to dispersed-phase-volume-fraction range of similar to 0.3-0.36. Broadening of loss-peaks vis-a-vis enhanced storage moduli in dynamic mechanical analysis (DMA) signifies the reduced mobility (of polyamide chains) and hence the enhanced stiffness. The electrical conductivity of the nanocomposites post-annealing decreased at temperatures above 100 degrees C demonstrating the temperature-sensitive morphology disruption (of the conductive PP-MWNT channels) in the nanocomposites.