Effect of nanoclay dispersion on the processing of polyester nanocomposites

The automotive industry is increasingly using resin transfer moulding (RTM) to produce composite body panels at high volumes and low costs. However, the processing parameters affect the physical and mechanical properties of the final finished part, which may have negative impact on the desired mechanical properties and surface finish. Unsaturated polyester (UP) mixed with organo nanoclay provides improved processing parameters which is a major concern for surface finish in RTM parts. Organo clays are silicate layers treated suitable to make them organophilic in order to be compatible with resin systems. UP systems give rise to numerous possible approaches in synthesizing nanocomposites. Three different techniques to synthesize nanocomposite systems, sequential mixing, solvent mixing and simultaneous mixing were studied and a suitable synthesizing technique was selected and used to make the nanocomposite systems. Two mixing approaches, three roll mill (TRM) machine and ultrasonication, were introduced to mix a pre-promoted UP resin/Low Profile Additive (LPA)/St system with organoclay. The effect of using these two approaches on the dispersion of the clays within the resin mix was studied using X-ray diffraction. Based on the results obtained from the X-ray analysis and viscosity measurements, ultrasonication was chosen as the optimum mixing method (OMM) for this system. One of the factors that influenced these results was the uncontrolled evaporation of styrene during the application of TRM. 0-5 wt% of Cloisite 20A was then added to the resin and mixed using optimum mixing method (OMM). The effect of adding clays on the viscosity, cure kinetics, storage modulus and glass transition temperature (Tg) was investigated. It was seen that the addition of clays increased the storage modulus of the resin samples, increased the viscosity, reduced the glass transition temperature very slightly and reduced the cure activity of the resin-clay system. Shrinkage tests on these resin-clay systems showed some reduction in shrinkage, however the typical shrinkage control mechanism was not observed.