Effect of Dispersion Conditions on the Thermo-Mechanical Properties of Functionalized Carbon Nanotube-Reinforced Vinyl Ester

S.M. Sabet, H. Mahfuz, J. Hashemi
Florida Atlantic University, US

Keywords: carbon nanotubes, nanocomposite, sonication, dispersion, thermo-mechanical properties

Summary:

To date, controlling the microstructure of carbon nanotube (CNT)-polymer composites remains a challenge due to high tendency of CNTs to aggregate. Proper dispersion of CNTs in the matrix has to be guaranteed to employ CNTs as effective reinforcement. In the current work, the dispersion of 0.25 and 0.5 wt.% carboxylic acid functionalized multi-walled carbon nanotubes (MWCNT-COOH) into a Derakane 8084 vinyl ester (VE) resin has been studied. In order to investigate the effect of dispersion conditions, various sonication parameters including mixing time and ultrasonication energy input have been examined during synthesizing process. Differential scanning calorimetry (DSC) results have shown 13°C increase in the glass transition temperature (Tg) of the 0.25 wt.% CNT/VE system when introducing total sonication energy of 60 KJ (Fig. 1a and c). However, a slight shift in Tg can be found in nanocomposites containing 0.5 wt.% CNTs (Fig. 1b and d). Room temperature 3-point flexural tests have been performed on rectangular specimens with different CNT contents and sonication energy levels (Fig. 2). Adding MWCNT-COOH nanoparticles reduces the ductility of VE matrix. It can be seen that the flexural modulus of the nanocomposites is enhanced by 15 and 24% as the sonication energy reaches to 60 KJ (for 0.25 wt.% CNT/VE system) and 15 KJ (for 0.5 wt.% CNT/VE system), respectively. This finding is consistent with the results of DSC (Fig 1c and d). The quality of CNT dispersion in the matrix has been monitored using the scanning electron microscopy (SEM) and nanoindentation mapping technique and correlated to the mechanical behavior of the material. Based on the resulting dispersion conditions, the optimum sonication parameters and nanoparticle loading have been determined.