Rheology, crystallization behavior under shear, and resultant morphology of PVDF/multiwalled carbon nanotube composites

Poly(vinylidene fluoride) (PVDF) composites containing multiwalled carbon nanotubes (MWNTs) in the range from 0.1 to 5 wt% were prepared at 220 A degrees C using a melt-mixer. The storage modulus (G') of the PVDF/MWNT composites increased with increasing MWNT content. In particular, there was a significant increase in G' between 1 and 3 wt%. In the Cole-Cole plot, the PVDF composites with up to 1 wt% MWNTs exhibited a single master curve with a slope of 1.25, but the composites containing 3 and 5 wt% MWNTs showed a decreased slope of 1.13 and 1.03, respectively. From the addition of 3 wt% MWNTs, the yield of the PVDF composites was observed in complex viscosity versus complex modulus plot with little dependence on the loss tangent (tan delta) on the frequency was shown. Both the induction time and crystallization time obtained from the G' versus time plot decreased with increasing MWNT content. The promoting effect of the MWNTs on the overall crystallization behavior was more profound at higher crystallization temperatures. Pure PVDF and PVDF with 0.1 wt% MWNTs showed only alpha phase crystals, but the PVDF composites with high concentrations of MWNTs (1-5 wt%) appeared to contain a mixture of beta and gamma phases in addition to the alpha phase.