Effects of the nanoparticles on the thermal expansion and mechanical properties of unsaturated polyester/clay nanocomposites

The thermal stability of nanocomposites based on unsaturated polyester resin (UP) and montmorillonite (MMT) clays is reported. The coefficients of thermal expansion (CTE) of both neat resin and nanocomposites with various concentrations of MMT were measured and it was found that the incorporation of clay particles reduced the CTE of the polyester resin. This reduction results greater at the lower MMT concentration tested (5 wt.%). Calorimetric tests also showed that the presence of nanoclays affects the kinetics of the curing reaction and the final degree of reaction reached by the unsaturated polyester resin. Bending and tensile tests revealed that higher percentages of MMT induced higher Young’s modulus while the introduction of a viscosity reducer resulted in worst mechanical performances. The fragile behaviour observed for the formulations with higher nanoclay content were confirmed by the typical cleavage surfaces of the fracture borders observed by scanning electron microscopy.