Synthesis and Micro-Mechanical Properties Of Epoxy-Alumina Nanocomposites

Abstract

It has been long time, but still continuous, for research and engineers to search and study the process, structure and properties of polymer nanocomposites, mainly because of their unique properties such as high strength-to-weight ratio. Many studies have shown that the incorporation of nano-sized particles have effectively reinforced the various properties of the polymers compared to that of the micron-sized particles reinforcement at the same percentage of particle loading. However, the effects of nano-sized particles depend strongly on the type, morphology, shape, size, amount, surface characteristic and the distribution of the particles incorporated into the polymer matrix. Therefore, it is essential to establish a polymer nanocomposite system that yields better properties without compromising other unique means of the polymer.

In this project, a series of epoxy-alumina nanocomposites with different particle shapes, sizes and surface chemistry were developed. This project was carried out in three phases. In phase one, six different type of epoxy-alumina nanocomposites was successfully synthesized using solvent assisted method. Characterization studies were then carried out in phase two to determine the microstructure and mechanical properties of the epoxy-alumina nanocomposites. The results revealed that alumina particles with platelet shapes that treated with acid surface modifier were yielded the best overall properties.

Phase three of this project focused on micro-mechanical properties characterization using nanoindentation technique. This was aimed to understand the mechanical properties of epoxy-alumina nanocomposites at localized micron to nano-meter scales. Compared to conventional mechanical testing techniques, nanoindentation technique provides measurements that allow the surface characterization on small specimen in simple and non-destructive way. The mechanical properties at specific location could be quantitatively correlated with the microstructure of the nanocomposites. Nanoindentation tests were conducted with different strain-rates, indentation depths and holding time durations. The result showed that nanoindentation technique is capable of determining the time- and rate- dependent properties of epoxy-alumina nanocomposites. A semi-empirical method based on elastic-viscoelastic-viscous model (EVEV) was used to characterize the viscoelastic behavior of nanocomposites. The creep equation from EVEV model is further used to derive the creep compliance of nanocomposites. Finally, the creep compliance was used to study the stress relaxation modulus of the nanocomposites. The results show that the creep compliance is useful in determining the localized creep behavior and the time-dependent mechanical properties (i.e, elastic modulus and hardness with time) of the material.

The characterization results in this project convincingly show that epoxy-alumina nanocomposites can lead to simultaneous improvement in various mechanical properties. The nanoindentation technique, in essence, indicates that this method can be applied to study the hardness, elastic modulus and viscoelastic (time- and rate- dependent) properties of epoxy-alumina nanocomposites under quick and simple manner. These findings will hence benefit both the plastic and characterization industry significantly.