Nanofiber fabrication in a temperature and humidity controlled environment for improved fibre consistency

To fabricate nanofibers with reproducible characteristics, an important demand for many applications, the effect of controlled atmospheric conditions on resulting electrospun cellulose acetate (CA) nanofibers was evaluated for temperature ranging 17.5 - 35°C and relative humidity ranging 20% - 70%. With the potential application of nanofibers in many industries, especially membrane and filter fabrication, their reproducible production must be established to ensure commercially viability.
Cellulose acetate (CA) solution (0.2 g/ml) in a solvent mixture of acetone/DMF/ethanol (2:2:1) was electrospun into nonwoven fibre mesh with the fibre diameter ranging from 150nm to 1µm.
The resulting nanofibers were observed and analyzed by scanning electron microscopy (SEM), showing a correlation of reducing average fibre diameter with increasing atmospheric temperature. A less pronounced correlation was seen with changes in relative humidity regarding fibre diameter, though it was shown that increased humidity reduced the effect of fibre beading yielding a more consistent, and therefore better quality of fibre fabrication.
Differential scanning calorimetry (DSC) studies observed lower melt enthalpies for finer CA nanofibers in the first heating cycle confirming the results gained from SEM analysis. From the conditions that were explored in this study the temperature and humidity that gave the most suitable fibre mats for a membrane purpose were 25.0°C and 50%RH due to the highest level of fibre diameter uniformity, the lowest level of beading while maintaining a low fibre diameter for increased surface area and increased pore size homogeneity. This study has highlighted the requirement to control the atmospheric conditions during the electrospinning process in order to fabricate reproducible fibre mats

Rubber-toughened epoxy loaded with carbon nanotubes: structure-property relationships

The paper reports on the preparation, structure and properties of ternary thermosetting blends, based on DGEBA epoxy, cured with 3,3′-DDS and modified by the addition of CTBN reactive liquid rubber and/or 0.3wt% of commercial multi- walled carbon nanotubes. The toughening effect of the phase-separated rubber particles is enhanced by the presence of the nanotubes, through a change in the morphology. In the absence of the rubber, the nanotubes alone produce a minimal effect upon the thermo-mechanical characteristics of the resin. However, the electrical conductivity of the cured resin samples is found to increase by five orders of magnitude, up to 3.6×10-3 S/m in the ternary bl

Effect of carbon nanotubes on the curing dynamics and network formation of cyanate ester resin

This paper is closed access.The effect of a pristine carbon nanotube (CNT), and three functionalised carbon nanotubes on the curing dynamics and network formation of a cyanate ester resin (CY), was investigated by means of differential scanning calorimetry (DSC), modulated temperature differential scanning calorimetry (MTDSC), field emission gun scanning electron microscopy (FEGSEM), Fourier transform infrared (FTIR) and Raman spectroscopies. Incorporation of the various carbon nanotubes showed different accelerating effects on cure of the CY. Addition of the pristine multi-walled carbon nanotube (MWCNT) did not show a prominent accelerating effect, whilst a carboxyl group functionalised multi-wall nanotube (MWCNT-COOH) displayed the greatest accelerating effect. For a hydroxyl group functionalised multi-walled carbon nanotube (MWCNT-OH)/CY system, the most pronounced accelerating effect was observed when 1 wt% to 2 wt% MWCNT-OH was added. Nano-scale dispersion of both the pristine and the functionalised multi-walled carbon nanotubes in the CY matrix was observed by using FEG-SEM. In contrast, micro-scale aggregation happened in a SWCNT-OH/CY system. The FTIR spectra monitored the formation of triazine rings in the CY and its composites with CNTs. The FTIR results indicated that the CNTs reacted with the cyanate groups of the CY to form oxime C=N-O bonds. The up-shifting of the bands for CNTs in Raman spectra confirmed nano-scale dispersion of MWCNTs in the CY matrix and strong interaction between the MWCNTs and the CY