Effect of Nanonoclay on the Curing and Thermal Conductivity of Unsaturated Polyester Resin

Abstract

This study was aimed at understanding effect of nanoclay on the heat transfer mechanism in a nanoclay-filled amorphous polymer-matrix composite. Nanocomposites of 1 to 15% by volume filler content were fabricated using the solution intercalation method. Dispersion of the nanoclay was done via ultrasonication. Differential Scanning Calorimetry (DSC) scans were done on the pristine polymer and those combined with nanoclay using both isothermal and dynamic modes of heating to determine the curing kinetics. Thermal conductivity measurements were performed at 50⁰C, 75⁰C, and 100⁰C, with the data fitted into existing mathematical models to define the conduction mechanism that could have transpired in the material. Thermal conductivity of the nanocomposites increased from 1.24±0.07 W/mK to 7.40±0.07 W/mK at 50⁰C with increasing nanoclay content with an apparent percolation threshold at 13% filler content. Fitting the experimental data with existing models for thermal conduction in composites revealed that the best fit is that with the Hasselman and Johnson model. Using this model, the effective thermal conductivity of the nanoclay was calculated to be around 15.78 W/m which is within the theoretical range of values of the bulk thermal conductivities of the nanoclay component compounds. Fitting the measured thermal conductivities to the scaling law revealed that the percolation threshold is around 12.49% filler content. Results from the DSC scans revealed that the extent of cross-linking generally decreases with increasing nanoclay content. Given the above considerations, it can therefore be said that the mechanism of conduction in the composite material involved the improved conduction in the matrix that is in series with the conduction along the nanoclay fillers, which have higher conductivities at their nanometer dimensions.