Advances in Engineering Advances in Engineering features breaking research judged by Advances in Engineering advisory team to be of key importance in the Engineering field. Papers are selected from over 10,000 published each week from most peer reviewed journals.
Significance Statement
Ultrasonication mixing method is a common technique to disperse carbon nanotubes (CNTs) into low-viscosity resins. To control properties of the final nanocomposite product, CNT dispersion needs to be optimized. Thus, the focus of the current investigation is to examine the role of ultrasonication energy in the dispersion of CNTs into a vinyl ester (VE) resin. In this regard, CNT/VE nanocomposites containing two CNT concentrations of 0.25 and 0.5 wt% were synthesized using ultrasonication technique. A variety of sonication parameters was selected to produce different nanotube dispersion states. Thermal and mechanical properties of nanocomposites and the quality of CNT dispersion were evaluated. By correlating the material properties and nanotube dispersion condition, a thermo-mechanical model is suggested. At a particular sonication energy level, CNT dispersion is optimum that provides the highest properties. This energy level is termed as a threshold energy meaning that sonication time and amplitude must correspond to this energy level to yield the most optimized dispersion and hence the maximum enhancement in properties. It is observed that at this threshold energy level, the glass transition temperature and elastic modulus of the pure VE polymer can be enhanced by 13 ºC and 24%, respectively. It is also observed that sonication threshold energy is linked with the concentration of nanoparticles. The lower the concentration, the higher is the threshold energy level. SEM observations suggest that this threshold energy is controlled by destruction of CNT structure. At higher nanotube contents, the threshold energy is reduced since a higher number of nanotubes are damaged even with a low energy input.
Journal Reference
Journal of Materials Science, 2015, Volume 50, Issue 13, pp 4729-4740.
S. M. Sabet1, H. Mahfuz 1, J. Hashemi1, M. Nezakat2, J. A. Szpunar2
[expand title=”Show Affiliations”]
- Department of Ocean and Mechanical Engineering, Florida Atlantic University, 777 Glades Road, Boca Raton, FL, 33431, USA
- Department of Mechanical Engineering, University of Saskatchewan, 57 Campus Dr, Saskatoon, SK, S7N 1L5, Canada [/expand]
Abstract
In the present paper, we report a systematic examination of sonication energy and the subsequent dispersion condition of nanoparticles in a vinyl ester resin. The nanoparticles were multi-walled carbon nanotubes (MWCNTs) functionalized with carboxylic acid groups. Two nanoparticle concentrations of 0.25 and 0.5 wt% with a variety of sonication amplitudes and duration were considered. Elastic moduli were determined using a 3-point flexural method and a nanoindentation technique. Glass transition temperatures (T g) were also evaluated by differential scanning calorimetry. The dispersion quality of MWCNTs was investigated by high-resolution scanning electron microscopy (HR-SEM). Results indicated that with both concentrations, there is a gradual increase in elastic modulus and T g up to a certain sonication energy level beyond which both properties decreased. However, this threshold energy level varied with MWCNT concentration. For example, the threshold energy level was 60 kJ in case of 0.25 wt% while it was only 15 kJ with 0.5 wt% concentration. It was also observed that regardless of the level of threshold energy, enhancement in properties remained more or less the same. This suggests that there is interplay between particle concentration and sonication energy that dictates the dispersion condition and hence controls the nanocomposite properties. It is further evidenced by SEM studies that nanotubes undergo significant structural changes such as length reduction even at lower energies that eventually limits the threshold level.
Go To Journal of Materials Science
