Multiwall carbon nanotubes filled polypropylene nanocomposites: Rheological and electrical properties

Thermal, Rheological, Mechanical, and Electrical Properties of Polypropylene/Multi-Walled Carbon Nanotube Nanocomposites

In this paper, nanocomposites based on polypropylene (PP) filled with up to 5 wt.% of multi-walled carbon nanotubes (MWCNTs) were investigated for determining the material property data used in numerical simulation of manufacturing processes such as the injection molding and extrusion. PP/MWCNT nanocomposite pellets were characterized for rheological behavior, crystallinity, specific volume and thermal conductivity, while injection-molded samples were characterized for mechanical and electrical properties. The addition of MWCNTs does not significantly change the melting and crystallization behavior of the PP/MWCNT nanocomposites. The effect of MWCNTs on melt shear viscosity is more pronounced at low shear rates and MWCNT loadings of 1-5 wt.%. However, with the addition of up to 5 wt.% of MWCNTs, the PP/MWCNT nanocomposite still behaves like a non-Newtonian fluid. The specific volume of the PP/MWCNT nanocomposites decreases with increasing MWCNT loading, especially in the MWCNT range of 1-5 wt.%, indicating better dimensional stability. The thermal conductivity, depending on the pressure, MWCNT wt.% and temperature, did not exceed 0.35 W/m·K. The PP/MWCNT nanocomposite is electrical non-conductive up to 3 wt.%, whereas after the percolating path is created, the nanocomposite with 5 wt.% becomes semi-conductive with an electrical conductivity of 10^-1 S/m. The tensile modulus, tensile strength and stress at break increase with increasing MWCNT loading, whereas the elongation at break significantly decreases with increasing MWCNT loading. The Cross and modified 2-domain Tait models are suitable for predicting the melt shear viscosity and specific volume as a function of MWCNTs, respectively. These results enable users to integrate the PP/MWCNT nanocomposites into computer aided engineering analysis.

Carbon nanofiber reinforced thermoplastic elastomer based on polypropylene/polybutadiene blend: theoretical modeling of Young’s modulus of the nanocomposites with respect to the orientation and agglomeration of carbon nanofiber

The effect of the concentration of carbon nanofibers (CNFs) on thermoplastic elastomer based on polypropylene/polybutadiene (PP/BR) blend (80/20) prepared by melt blending process was investigated. The morphological properties are reported in combination with the mechanical and rheological properties of the nanocomposites. The dispersion of CNFs examined by transmission electron microscopy shows uniform dispersion of CNFs in the PP matrix. The mechanical performance is found to be in line with the morphological structure observed in scanning electron microscopy. Tensile strength and Young’s modulus of the PP/BR blend increase with an increase of filler content up to 3 wt%. The modified Halpin-Tsai equation that accounts for the effect of orientation and agglomeration of CNF was used to evaluate the Young’s modulus of the nanocomposite. The dynamic rheological analysis in the frequency sweep experiment shows that the introduction of CNF in the PP/BR blend improves the complex viscosity (ƞ*), storage modulus (G′), and loss modulus (G″) in the low-frequency region.