Comparative analyses of the electrical properties and dispersion level of VGCNF and MWCNT: Epoxy composites

The electrical properties and dispersion of vapor‐grown carbon nanofibers (VGCNF) and multiwalled carbon nanotubes (MWCNT)—epoxy resin composites are studied and compared. A blender was used to disperse the nanofillers within the matrix, producing samples with concentrations of 0.1, 0.5, and 1.0 wt % for both nanofillers, besides the neat sample. The dispersion of the nanofillers was qualitatively analyzed using scanning electron microscopy, transmission optical microscopy, and grayscale analysis. The electrical conductivity and the dielectric constant were evaluated. The percolation threshold of MWCNT epoxy composites is lower than 0.1 wt % while for VGCNF lies between 0.1 and 0.5 wt %. The difference on the dispersion ability of the two nanofillers is due to their intrinsic characteristics. Celzard's theory is suitable to calculate the percolation threshold bounds for the VGCNF composites but not for the MWCNT composites, indicating that intrinsic characteristics of the nanofillers beyond the aspect ratio are determinant for the MWCNT composites electrical conductivity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

A biomimetic approach to enhance selectivity of direct dyes using VGCNF in polysulphone based nanofiltration membranes

Mussel inspired chemistry has gain tremendous interest in the field of membrane science and technology. Inspired by the adhesive proteins present in mussels, approaches involving the dopamine to modify the surfaces have become the predominantly striking strategy. In this work, an effective strategy is proposed to improve the selectivity of vapour grown carbon nanofibers (VGCNF) via the bio inspired polydopamine (PDA) functionalization approach. The varying concentration of modified VGCNF (D-A-VGCNFs) were employed in polysulphone (PS) membrane. The morphological characteristics of membranes were evaluated by SEM and AFM. Data depicted the uniform distribution of nanofibers (NFs) in the media and amended microstructure of the membranes. Modified membrane having the maximum amount of D-A-VGCNFs (DM5) proved to be more hydrophilic in nature with contact angle value of 57° whereas the CA value of pure PS membrane (DM0) was 76°. The performance test confirmed that the DM5 has enhanced dye rejection ratios which are 95%, 97% and 96% with improved permeate fluxes (like 56 L/m².h, 40 L/m².h and 53 L/m².h for Direct Red 31, Direct Blue 86 and Direct Yellow 4 dyes respectively. Furthermore, DM5 showed much better anti-fouling properties after several cycles as compared to DM0. So, this work proved to be a milestone in the applications of nanofiltration (NF) membranes to remove the dyes from the textile wastewater.