Optimising the Properties of Polymer Composites: Low Weight/ High Strength Composites for Commercial Applications

M. Hayward, J. Johnston, T. Dougherty, K. de Silva
Victoria University of Wellington,
New Zealand

Keywords: polymer composites, interfacial adhesion, hollow polymer microsphere, vinyl ester, advanced materials

Summary:

Vinyl ester polymers have an excellent resistance to harsh and corrosive environments. This results in their wide-spread use as a polymer composite material for multiple applications in various industries such as marine materials, swimming pools and solvent storage tanks. Fibre-reinforced polymer (FRP) composites, which use vinyl ester resins as the matrix material, are low-density with superior mechanical properties, such as strength and stiffness. Further improvements to the strength-to-weight ratio of the vinyl ester matrix is of constant interest to maximise the performance of the FRP composite in high-end commercial applications. Dry, expanded, hollow polymer microspheres (PMS) have an extremely low density and also exhibit high elasticity and low moisture absorption. PMS can be incorporated into a polymer composite to reduce the overall density, improve workability and increase resilience of the material. In this study, copolymer-based PMS were dispersed into a commercial vinyl ester resin with the aim of reducing the density of the composite without compromising strength. The surface groups on the PMS were functionalised with hydroxyethyl methacrylate (HEMA) to improve the interfacial adhesion between the additive and matrix in order to maximise the overall strength of the composite material. The interfacial adhesion in the composites was analysed by studying the fracture surfaces via scanning electron microscopy (SEM) which provided visual evidence for enhanced interfacial binding of the HEMA-functionalised PMS to the resin matrix compared to the unfunctionalised spheres. The mechanical properties and densities of the PMS-vinyl ester composites were measured and compared for different volume fractions of PMS to determine which composite conditions resulted in the best composite properties. It was found that the HEMA-PMS composite successfully reduced the density and enhanced the mechanical properties of the composite resulting in a significant increase in the specific strength of the material.