Pyrolysis at Slow or Programmed Rates

Although for most analytical pyrolysis techniques it is advisable to heat the sample to its final temperature as rapidly as possible, there are times when just the opposite is required. To simulate thermal processes, such as TGA on a small scale, or to analyze the degradation products produced from a sample as they are generated, slower, controlled heating is required. These slow-rate experiments demonstrate, for example, that polyfvinyl chloride) degrades in a two-step process, producing HCl at a relatively low temperature and aromatics at elevated temperatures. 

While a sample material is slowly heated to its degradation temperature, the volatile products may be swept by a carrier gas into an analytical instrument or collected onto a trap for analysis as a composite. Alternatively, the sample may be pyrolyzed directly in the analytical instrument, while scans are collected continuously. This produces a time-resolved picture of the production of specific products, as measured by the abundance of specific masses or absorbance at specific wavelengths. 

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