Kinetics of Nonisothermal Degradation of Some Polymer Composites: Change of Entropy at the Formation of the Activated Complex from the Reagents

Abstract

Studying the nonisothermal kinetics of degradation of rice husks in air or nitrogen atmosphere, polypropylene and tetrafluoroethylene-ethylene copolymer filled with different quantities of rice husks flour or the products of its thermal degradation, namely "white" or "black" rice husks ash, a linear dependence was observed between the ln A and E A , known as the kinetic compensation effect or theta rule. A linear relationship was also established between E A and the change of the entropy ΔS / = for the formation of the activated complex from the reagents. These dependences are related to the assumption of identical kinetic mechanisms of thermal degradation of the composites studied. The negative values of ΔS / = obtained show that the activated complex is a "more organized" structure than the initial reactants and that these reactions may be classified as "slow" ones. It may be concluded that the products of the thermal degradation of rice husks in a fluidized bed reactor can successfully replace the more expensive synthetic fillers to obtain different polymer composites. These polymer composites can lead to the futuristic "organic-inorganic hybrid materials" with specific properties.

The influence of impregnating chemicals on the carbonization process of viscose fiber cloths

“…In this case of S > 0 indicating a thermal decomposition reaction of viscose fiber might occur with non structured activated complex comparing with the initial reactants. This can be suggested that the carbonization reaction is classified as fast [8]. The obtained experimental data from …”

“…Carbonization is a conversion of an organice substance in to carbon or a carbon-containing reidue through pyrolysis [7,8]. The carbonization reaction under thermal decomposition may take play as follows:…”

“…The carbonization continued to 700 0 C with the fiber mass remaining in 20 %. According to [8] during carbonization process, thermal decomposition of raw materials eliminates non-carbon elements such as oxygen, hydrogen and nitrogen lead to a carbon skeleton (char) with a rudimentary pore structure.…”

Electrochemical investigations of some newly synthesized arylazapyrazole derivatives

“…The negative values of DS # were obtained (Table 3), which showed that there forms an adsorbed ''activated complex'' on the electrode surface which is more organized than the initial reactants [18][19][20]. The decrease in the negative values of entropy of activation with increasing temperature shows that the 'organized structure' is disturbed with increasing temperature which results in the decreased values of charge transfer coefficient and that of k s .…”

Effect of glycidylisobutyl–POSS on the thermal degradation of the epoxy resin

“…DS* indicates the degree of arrangement based on the initial reagents. The obtained values are used to classify the reaction as ''fast'' or ''slow'' based on the signal of the values [26,27]. The reaction is classified as ''normal'' when the formation of the activated complex is not controlled by significant changes in DS* (DS* & 0).…”