Other parameters affecting analytical pyrolysis

The value of Teq and the conditions of attaining Teq temperature by the sample are not controlled solely by the heat source of the pyrolyzer but also by the sample properties and the pyrolyzer construction [9, 10], This is caused by the variations in the process of heat transfer to the sample from the heat source. For example, sample characteristics such as the mass m and the specific heat c will influence the increase of the sample temperature by the formula AT = Q/(m c). In addition, phase changes and exothermic and endothermic chemical reactions in the sample may play an important role in temperature rise. To diminish the variations determined by these processes, a very 

The effect of sample size on the pyrolysate composition can be exemplified for the pyrolysis of a polyfvinyl ethyl ether) sample. The polymer has the formula 

The differences are likely generated by the change in the temperature raise profile, and in the temperature distribution within the sample. Further discussion on pyrolysis of poly(vinyl ethyl ether) can be found in Section 5.5.3). 

The change in sample size has been shown to influence product ratios, fractional conversions, and rates of pyrolysis for several polymers [14]. However, the dependence of pyrolysis results on sample size does not have only a negative impact on data reproducibility. This effect may reveal mechanistic features of the pyrolysis process, such as secondary reactions that occur during the residence time of primary products in the melt and diffusion-restriction of the interaction of long-chain radicals, when the thickness of the degrading film is comparable with the diameter of the hydrodynamic volume of the polymer molecules. 

The actual temperature acquired by the sample during pyrolysis can be monitored using optical pyrometry or can be standardized between different pyrolyzers using a model compound. The procedure is based on the dependence of the composition of the pyrolysis products on temperature. One such compound chosen as a standard is an isoprene/styrene copolymer, trade name Kraton 1107 [15] (see Section 4.2). 

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