Properties and thermal degradation kinetics of polystyrene/organoclay nanocomposites synthesized by solvent blending method: Effect of processing conditions and organoclay loading

摘要

In this study, intercalated/exfoliated polystyrene (PS)/organoclay nanocomposites containing different concentration of organoclay have been prepared via solvent blending method, using xylene as a solvent. Some resulting intercalated nanocomposites are transformed to exfoliated nanocomposites by increasing the refluxing temperature or refluxing time for a constant organoclay loading. The X-ray diffraction results reveal the formation of intercalation/exfoliation of organoclay in the PS matrix. The Fourier transform infrared spectroscopy and transmission electron microscopy results confirm the presence of nanomaterial in PS/organoclay nanocomposites. Completely exfoliated nanocomposites are achieved by decreasing the content of organoclay and elongating the refluxing temperature or refluxing time. Thermogravimetric analysis data show that the PS/organoclay nanocomposites have significant enhanced thermal stability. When 50% weight loss is selected as a point of comparison, the thermal decomposition temperature (Td) of the exfoliated PS/organoclay nanocomposites with 7 wt % of organoclay is 17°C higher than that of pure PS. Thermal decomposition temperature of exfoliated PS/organoclay nanocomposites is better than that of intercalated nanocomposites for a constant organoclay loading. The glass transition temperature (T _g) of PS/organoclay nanocomposites is ～ 7.1-8.6°C higher than that of pure PS. The thermal degradation activation energy of the nanocomposites is determined via Coats-Redfern method. The improvement of thermal stability of nanocomposites is also confirmed by increasing the activation energies (E_a) and the integral procedural decomposition temperature. Criado method is finally used to determine the degradation reaction mechanism of various samples. The water uptake capacity of PS/organoclay nanocomposites is negligible when compared with pure PS.