Polymer-evolved gases

Recently Hegazy et al. investigated the gas evolution from various aromatic polymers by y- and electron-irradiation under vacuum at ambient temperature [60], Table 3 shows the summarized results of gas analyses evolved by y-irradiation. The structure of the polymers evidently exerts great influence on the yield and the component of gases evolved. Furthermore, the gas evolution is... 

Doping unsublimed and sublimed stacked [Al(F)Pc] and [Ga(F)Pc] under various conditions with iodine leads to organic solids of high conductivity (Table 10) The Raman spectra show that (tojmg results in the reduction of iodii% to Jf. It is disadvantageous, that these polymers evolved iodine when stored at T = 300 K. Moreover, the iodine doped (67) is indefinitely stable in air J2 may be removed by heating above 373 K. Hie advantage of polymer (79) is the possibility to prepare thin films by sublimation. 

Grayson et al. (10) investigated untreated, vacuum-baked at 120°C, and fractionally reprecipitated PS. They analyzed the various samples for indigenous volatile content by vaporization-gas chromatography/mass spectrometry (33,36,37) and found that fractional reprecipitation was the only effective method to remove the volatile fraction from PS. Further, stress MS experiments with PS samples prepared from the fractionally reprecipitated polymer evolved only a trace of styrene monomer. 

The commercial process for the production of vinyl acetate monomer (VAM) has evolved over the years. In the 1930s, Wacker developed a process based upon the gas-phase conversion of acetylene and acetic acid over a zinc acetate carbon-supported catalyst. This chemistry and process eventually gave way in the late 1960s to a more economically favorable gas-phase conversion of ethylene and acetic acid over a palladium-based silica-supported catalyst. Today, most of the world s vinyl acetate is derived from the ethylene-based process. The end uses of vinyl acetate are diverse and range from die protective laminate film used in automotive safety glass to polymer-based paints and adhesives. 

Dynamic headspace GC-MS involves heating a small amount of the solid polymer sample contained in a fused silica tube in a stream of inert gas. The volatile components evolved on heating the sample are swept away from the sample bulk and condensed, or focused on a cryogenic trap before being introduced onto the chromatographic column via rapid heating of the trap. The technique can be used qualitatively or quantitatively DHS-GC-MS is considered to be well suited towards routine quantitative analysis. 

Although the majority of studies focus on the solid state, many applications focus more or additionally on the volatile products arising from polymer degradation. Evolved gas analysis (EGA) from thermal analysers and pyrolysers by spectroscopic and coupled chromatography-spectroscopy techniques can be particularly important from a safety and hazard viewpoint, since data from such measurements can be used to predict toxic or polluting gases from fires, incinerators, etc. 

Gas chromatographic methods are used for the analysis of organic additives extracted from polymers with solvents and other liquid media or evolved by heating. 

This is the primary degradation process accompanying processing of the polymer. The early stage of the dehydrochlorination process is uncomplicated by interfering processes. The only product observed by evolved gas analysis is hydrogen chloride (scheme 1). The sample... 

The early patent disclosures have claimed the application of a wide spectrum of gas-evolving ingredients and phosphorus-based organic molecules as flame retarding additives in the electrolytes. Pyrocarbonates and phosphate esters were typical examples of such compounds. The former have a strong tendency to release CO2, which hopefully could serve as both flame suppressant and SEI formation additive, while the latter represent the major candidates that have been well-known to the polymer material and fireproofing industries.The electrochemical properties of these flame retardants in lithium ion environments were not described in these disclosures, but a close correlation was established between the low flammability and low reactivity toward metallic lithium electrodes for some of these compounds. Further research published later confirmed that any reduction of flammability almost always leads to an improvement in thermal stability on a graphitic anode or metal oxide cathode. 

Gas chromatography (GC) and mass spectrometry (MS) can be coupled to the TGA instrument for online identification of the evolved gases during heating pyrolysis-GC/MS is a popular technique for the evaluation of the mechanism and the kinetics of thermal decomposition of polymers and rubbers. Moreover, it allows a reliable detection and (semi)quantitative analysis of volatile additives present in an unknown polymer sample. 

As described in Section 3 of Chapter 2, multi-electron processes are important for designing conversion systems. Noble metals are most potent catalysts to realize a multi-electron catalytic reaction. It is well known that the activity of a metal catalyst increases remarkably in a colloidal dispersion. Synthetic polymers have often been used to stabilize the colloids. Colloidal platinum supported on synthetic polymers is attracting notice in the field of photochemical solar energy conversion, because it reduces protons by MV to evolve H2 gas.la)... 

This test is used most frequently it is an accelerated test designed to determine the stability of an explosive and also the compatibility of an explosive with a polymer or contact material. The assembly of the set-up and method of its determination are described in detail in the literature [14]. A dried and accurately weighed sample of a secondary explosive (5.0 0.01 g) or of a primary explosive (1.0 0.01 g) is placed in the heating tube followed by its assembly and evacuation. The heating tube is immersed in a constant temperature bath (100 °C or 120 °C) for a period of 40 h and the volume of evolved gases is recorded. Most explosives or explosive formulations yield less than 1 cm3 of gas per gram of an explosive during 40 h at 120 °C. 

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