Thermal degradation uptake

Table 2.12 Interesting Set of Properties Obtained for Synthesized Sulfonated Fluorinated Poly(Arylene Ether)s Including Thermal Degradation, Mechanical Properties, Oxidative Stability, Water Uptake, Swelling and Proton Conductivity for Variations of DS... 

The evaluation of thermal degradation may be suggestively done by the comparison between chemiluminescence and oxygen uptake measurements (Figs. 22a and b) which both of them are based on the chemical modifications caused by oxygen diffusion. They similarly allow to order several polymeric materials based on their stability. Ozawa s group found for some polyolefins the following sequence of stability [9001] ... 

Fig. 22 Comparative results for thermal degradation of some polyolefins by (a) chemiluminescence measurements and (b) oxygen uptake. Testing temperature 140 °C. The data were taken from [9001]. (1) HDPE, (2) P4MP, (3) PP, (4) PB.

When a compound crystallizes from solution, the crystals may contain solvent of crystallization. The compound is then called a solvate, and if the solvent is water, the compound is a hydrate. The presence of the solvent is revealed by elemental analysis, and thermogravimetric analysis (TGA) shows whether the solvent molecules are loosely or strongly bound in the crystal lattice. More generally, TGA is used to investigate the thermal degradation of inorganic compounds or polymers or the gas uptake of a solid (e.g. H2 uptake by WO3). A TGA instrument is able to simultaneously heat (at a constant rate) and record the mass of a sample. Samples are usually heated in air or N2, or in an... 

Kinetic curves of weight loss, oxygen uptake, and elimination of carbon monoxide and carbon dioxide in the thermal degradation of polybenzoxazoles and polybenzimidazoles are S-shaped degradation is believed to occur via a radical-chain mechanism, similar to that of benzene oxidation at high temperatures. High values of the effective energy of these decompositions (142-159 kj/mol) provide evidence for the radical-chain mechanism [14],... 

Catalytic oxidation of ozonides over platinum appears to be accompanied by the same ester by-product disadvantage found in the thermal process. Chain degradation by other reactions is less serious, however, and transesterification does not occur. The method can therefore be used to prepare a half-ester of a dicarboxylic acid from an ester of a suitable unsaturated acid. If ozonide autoxidation occurs by the route, ozonide — aldehyde — peracid, with the latter acting as precursor of both acid and ester products (20-24), it is interesting to compare reaction rates observed in the present study with the rate of uptake of oxygen by... 

Uptake of oxygen by a polyethylene film sample during thermal oxidation at I00°C and photo-oxidation at 30 °C (from Kelen, T, Polymer Degradation, Van Nostrand Rheinhold, 1983). 

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