Accounting for the lack of nano-effect in a thermoset/clay nanocomposite: A positron annihilation study

[摘要] The effect of nanoclay dispersion on the thermo-mechanical properties of an unsaturated polyester thermoset resin was studied by flexural and dynamic mechanical property measurements. Transmission electron microscopy studies revealed intercalated clay dispersion morphology in the nanocomposites. The thermomechanical measurements showed a steady decrease in the flexural strength and a relaxation temperature, with only moderate increase in the storage modulus at 1% clay loading, followed by a drop at higher clay loadings. In order to understand the absence of nano-effect in this case, free volume measurements were carried out by using positron annihilation lifetime spectroscopy. A bimodal distribution of o-Ps life times was observed. Nanoclay loading resulted in the increase of the o-Ps intensity corresponding to the longest life time as well as free volume fraction suggesting diminished chain packing efficiency in the nanocomposites. We posit that nanoclay induced decreased chain packing efficiency and the presence of higher free volume size elements might cause deterioration in mechanical properties of the nanocomposites.

[发布机构] Polymer Division, Naval Materials Research Laboratory, Shil-Badlapur Road, Ambernath, Maharashtra; 421506, India^1;Radiochemistry Division, Bhabha Atomic Research Centre, Mumbai; 400085, India^2

[效力级别] 化学

[关键词] Bimodal distribution;Dynamic mechanical property;Nanoclay dispersion;Positron annihilation lifetime spectroscopy;Relaxation temperature;Thermomechanical measurements;Thermomechanical properties;Unsaturated polyester