Cooperative rearrangement region in nanoclay‐reinforced unsaturated polyester resin

Abstract

The effect of nanoclay on structural relaxation of unsaturated polyester (UP) resin containing 3 wt% Cloisite 10A (UP/10A), 3 wt% Cloisite 30B (UP/30B), and the neat resin was investigated by differential scanning calorimetry (DSC) and temperature modulated differential scanning calorimetry (TMDSC). X‐ray diffraction and transmission electron microscopy were used to evaluate the morphology of UP/10A and UP/30B nanocomposites. According to the strong‐fragile concept proposed by Angel, the values of the fragility index m were determined. The average size of a cooperative rearranging region (CRR) at the glass transition temperature ( T g ) was then calculated. Considering the significant increase in δ T (the mean temperature fluctuation) of UP/10A, it was concluded that UP/10A system was more heterogeneous than the neat UP and UP/30B specimen. Significant drop in T g accompanied by an increase in δ T and a decrease in characteristic length of cooperativity at glass transition temperature (ξ T g ) might be a sign of existence of smaller average CRR sizes in UP/10A nanocomposites. Results showed that the increase in the concentration of styrene between galleries of Cloisite 10A caused a decrease in styrene content outside the nanoclay layers leading to diminishing of crosslink density and as a consequence the decrease of ξ T g . POLYM. ENG. SCI., 54:2859–2865, 2014. © 2014 Society of Plastics Engineers