Degradation product onset temperature

As commercially pure materials, the ethyleneamines exhibit good temperature stabiUty, but at elevated temperatures noticeable product breakdown may result in the formation of ammonia and lower and higher mol wt species. This degradation becomes mote pronounced at higher temperature and over longer time periods. Certain contaminants, such as mineral acids, can lower the onset temperature for rapid thermal decomposition. The manufacturer should be contacted and thermal stabiUty testing conducted whenever ethyleneamines ate mixed with other materials. 

About sixty milligramme of the GEPN/dicy system was heated in the TGA - coupled - FTIR/MS from 30°C to 400°C (rate 5°C/minute) to measure straightforward the volatile thermal degradation products of the cured resin matrix material. The GEPN/dicy sample was cured (according to a DSC experiment under the same thermal conditions) between 160°C and 240°C. Detectable mass losses due to thermal degradation processes started at 295°C (onset temperature). The mass loss rate proved to be maximal at 385°C/390°C. 

The antimony product was soluble in DMSO and partially soluble in HMPA, IMPO, DMF, and sulfolane. The antimony product melts at about 156 °C becoming black at 222 °C with the coloration consistent with degradatoin of the product. Onset of coloration precedes the final darkening to black so that some thermal-induced degradation begins at a lower temperature. 

Analytical determination of polymer additives is sometimes complicated, as evaporation of volatile fractions and degradation can occur simultaneously. Py-GC/MS has shown the potential to separate and finally identify volatiles in liquid polymers or oils, which are usually charged with additives. The onset temperature of thermal degradation of a liquid polymer and the characteristics of the pyrolysis at higher temperatures can be assessed by studying the volatiles produced. However, this approach requires that the true thermal degradation products be identified and not just any components that are simply evaporated from the sample. An innovative method, called the temperature-sequence GC method, was proposed. 

In this method the same sample is subjected to a sequence of 10 sec pyrolyses at increasing temperatures, and for each temperature the complete chromatogram of the volatile products is recorded. This method has the potential to provide good characterization of the volatile products, but its disadvantage is that not enough temperature steps can be taken to allow the onset temperature of degradation. 

CoupiGd Pyrolysis Techniques. Perhaps the most powerful techniques currently available are those in which the polymer is pyrolyzed for a short time in a pyrolysis system directly coupled to a modem analytical instmment capable of analysis of the volatile products. Although direct pyrolysis coupled with ftir is available, the most common techniques have been gas chromatography, mass spectroscopy, and combinations of the two. In contrast to tga, these techniques provide no real information on the onset temperature of degradation or on the number of distinct stages, but they can give very detailed information about the products of reaction. 

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