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One-stage degradation process was observed for a poly(methyl methacrylate) (PMMA) sample. The fractional conversion αmax at the maximum reaction rate is thus applied to determine reaction order of the thermal degradation. It is found that the PMMA degraded in the first order kinetics with weight loss. This is consistent with the fact that PMMA thermally degrades into its monomer. Activation energy was calculated. Compensation effect of the Arrhenius parameters is also found. [Copyright &y& Elsevier]

Abstract: The structural and electronic properties of hydrogenated armchair and zigzag SWCNTs with carbon ad-dimer (CD) defect were investigated by means of the B3LYP hybrid density functional method using 6-31G∗ basis set. It is found that the chemisorptions of two hydrogen atoms inside and outside the CD defective SWCNTs are exothermic processes. Exohedral nanotube adsorption is energetically more favorable than endohedral adsorption. These results are in agreement with hydrogen on pristine nanotubes. The positional preference for the chemisorption of two hydrogen atoms is the same for the CD defective armchair and zigzag nanotubes. However, the reaction energy of two hydrogen atoms on the exterior sidewalls of CD defective SWCNTs is almost independent of the tube diameter. This is different from the results reported on pristine nanotubes. The calculated energy gaps indicate that the hydrogen-chemisorbed CD defective armchair tubes are always wide energy gap structures, while the hydrogen-chemisorbed CD defective zigzag tubes have significantly lower gaps. The HOMO–LUMO gap and reaction energy for the chemisorption of more hydrogen atoms on the exterior sidewalls of CD defective armchair SWCNTs were also explored. [ABSTRACT FROM AUTHOR]