Shear and extensional rheology and flow-induced orientation of carbon nanofiber/polystyrene melt composites

Rheological Properties of MWCNT-Doped Titanium-Oxo-Alkoxide Gel Materials for Fiber Drawing

A strategy of doping by multi-walled carbon nanotubes (MWCNT) to enhance mechanical strength and the electrical conductivity of ceramic fibers has nowadays attracted a great deal of attention for a wide variety of industrial applications. This study focuses on the effect of MWCNTs on rheological properties of metal alkoxide precursors used for the preparation of nanoceramic metal oxide fibers. The rheological behavior of MWCNT-loaded titanium alkoxide sol precursors has been evaluated via an extensional rheometry method. A substantial decrease in elongational viscosity and relaxation time has been observed upon an introduction of MWCNTs even of low concentrations (less than 0.1 wt.%). A high quality MWCNT/nanoceramic TiO₂ composite fibers drawn from the specified precursors has been validated. The MWCNT percolation, which is mandatory for electrical conductivity (50 S/m), has been achieved at 1 wt.% MWCNT doping.

Effect of Flow Induced Orientation of Carbon Nanotubes on the Capillary Extrusion Behavior of Low-Density Polyethylene

The effect of carbon nanotubes (CNTs) on the capillary extrusion behavior of low-density polyethylene (PE) was investigated. From the linear viscoelasticity and the morphology observation, it was found that the CNTs were well dispersed throughout the PE matrix and our system belonged to the semi-dilute regime. The strain hardening, which quantifies the extension of the PE chain, decreased by presence of CNTs in the uniaxial elongational deformation. In contrast, the normal stress difference was almost unaffected by CNTs in the shear deformation. The capillary extrusion behavior revealed that swell ratio decreased with increasing the CNT content although melt fracture was promoted. We summarize that the suppression of swell and promotion of melt fracture are attributable to the orientation of CNTs.