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

Abstract

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 (T d ) 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 $ 7.1-8.6C 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.

Thermal and flammability study of polystyrene composites containing magnesium–aluminum layered double hydroxide (MgAl–C16 LDH), and an organophosphate

“…4b). Both the TG and DTG plots show that pure PS (commercial; molecular weight &230,000 g mol -1 ) degradation under the heating profile used here is a one-step process with the temperature at maximum rate of degradation (T max ) being 413°C, which is in agreement with values reported in the literature [36]. With the addition of the additives, there was an increase in the value of T max of up to 31°C for PS compounded with 10 mass% DPP with insignificant changes being observed for the other composites.…”

“…However, there were little increases in the composites which had the LDH additive, with the composite having 5 mass% loading of the LDH having a higher increase than the one with 10 mass% loading. The decrease in thermal stability at higher clay loading observed here has been reported elsewhere and has been attributed to the large content of organic anions which destabilize char formation process during pyrolytic degradation [36,37]. The increased thermal stability for a loading of 10 mass% of DPP may be due to the radical trapping effect of DPP that increases the thermal stability and also enhances charring.…”

Limitations of model-fitting methods for kinetic analysis: Polystyrene thermal degradation

“…A lack of plot linearity and inconsistent activation energy values are observed and the authors conclude that simple first or second order models are good enough for determining the activation energy and, therefore, constitute "the most suitable design approach". Other works employing similar single-curve model-fitting kinetic procedures reached analogous conclusions (Ahmad et al , 2010, Ahmed and Gupta, 2009, Krishna and Pugazhenthi, 2011. However, some other works, employing isoconversional and non-linear model fitting methods, have revealed the unsuitability of nth order reaction models and suggest an acceleratory model instead (Chen et al , 2007, Sanchez-Jimenez et al , 2010, Snegirev et al , 2012, Vyazovkin et al , 2004.…”

Optical Properties of Poly(2-(5-bromo benzofuran-2-yl)-2-oxoethyl methacrylate)/Organoclay Nanocomposites

“…An intercalating agent of clay containing a polymerizable aromatic group with long alkyl chain, vinylbenzyldimethylhexadecylammonium chloride (VHAC), was carefully chosen. It has good affinity with benzofuran-derived monomer and uses it to functionalize pristine clay (Na-MMT) for the preparation of exfoliated benzofuran polymer/clay nanocom- [29].…”

“…Clay is a simple and natural mineral, very abundant, and the sheet structure is well known, used in many fields, environmental friends. In particular, montmorillonitetype clay (MMT) is the most widely chosen nanofiller for the preparation of polymer/clay nanocomposites due to its important advantages [29]. In the study of physical properties of polymers, optical absorption spectrum is one of the most important tool for understanding band structure, electronic properties, and optical constants (refractive and absorption indices) of pure and composite polymers [30].…”