The results of recent research indicate that the introduction of layered silicatemontmorillonite -into polymer matrix results in increase of thermal stability of a number of polymer nanocomposites. Due to characteristic structure of layers in polymer matrix and nanoscopic dimensions of filler particles, several effects have been observed that can explain the changes in thermal properties. The level of surface activity may be directly influenced by the mechanical interfacial adhesion or thermal stability of organic compound used to modify montmorillonite. Thus, increasing the thermal stability of montmorillonite and resultant nanocomposites is one of the key points in the successful technical application of polymer/clay nanocomposites on the industrial scale. Basing on most recent research, this work presents a detailed examination of factors influencing thermal stability, including the role of chemical constitution of organic modifier, composition and structure of nanocomposites, and mechanisms of improvement of thermal stability in polymer/montmorillonite nanocomposites.

In previous part of this work factors influencing the thermal stability of polymer nanocomposite materials were indicated, such as chemical constitution of organic modifier, filler content, nanocomposites' structure and the processing-dependent degree of homogenization of nanofiller, were presented. In this part the basic changes in thermal behaviour of different polymeric matrixes (e.g. polyolefins, polyamides, poly(vinyl chloride) and styrene-containing polymers) upon addition of montmorillonite have been described. Brief description of the kinetics of the decomposition process in inert and oxidative environment, as well as analysis of volatile and condensed products of degradation, have also been presented.

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Unreported graft copolymer of 2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS) with sodium carboxymethylcellulose (Na-CMC) was synthesized and reaction conditions were optimized using a bromate/ thiourea redox pair under an inert atmosphere at 40°C. Grafting ratio, add on, and conversion increase as the concentration of thiourea and [H ϩ ] increases up to 3.6 ϫ 10 Ϫ3and 0.6 ϫ 10 Ϫ2 mol dm Ϫ3, respectively, while on increasing the concentration of bromate ion and Na-CMC, grafting ratio, add on, and conversion decrease. The samples of Na-CMC and grafted Na-CMC with AMPS were subjected to thermogravimetric analysis, with the objective of studying the effect of grafting of AMPS on the thermal stability of graft copolymer. The graft copolymer was found to be more thermally stable than pure Na-CMC. Comparing the IR spectra of pure with grafted Na-CMC confirm the evidence of grafting.

A xanthan gum-g-N-vinyl formamide graft copolymer was synthesized through the graft copolymerization of N-vinyl formamide (NVF) onto xanthan gum with an efficient system, that is, potassium monopersulfate (PMS)/Ag(I) in an aqueous medium. The effects of the concentrations of Ag(I), PMS (KHSO 5 ), hydrogen ion, xanthan gum, and NVF along with the time and temperature on the graft copolymerization were studied by the determination of the grafting parameters (grafting ratio, add-on, conversion, grafting efficiency, and homopolymer) and the rate of grafting. The maximum grafting ratio was obtained at a 0.6 g/dm 3 concentration of xanthan gum. All the parameters showed an increasing trend with an increasing concentration of peroxymonosulfate, except the homopolymer percentage, which showed a decreasing trend. The grafting ratio, add-on conversion, grafting efficiency, and rate of grafting increased with the concentration of Ag(I) increasing from 0.8 ϫ 10 Ϫ2 to 1.2 ϫ 10 Ϫ2 mol/dm 3 . The optimum time and temperature for the maximum degree of grafting were 90 min and 35°C, respectively. The graft copolymer was characterized with IR spectral analysis, thermogravimetric analysis, and differential calorimetry analysis.