Helena Jönsson, Inger Ericsson
Analytical pyrolysis has long been used for analysis of non-volatile substances, but mainly as a fingerprinting technique. Through better understanding of the thermal degradation process it is possible to extract much more information of the processed sample. Since the same pyrolysis product can have different origins the study of formation rates can give important additional information. The formation rates are most easily determined by sequential pyrolysis, where the same sample is pyrolyzed a number of times under the same conditions. Repeated at different temperatures an Arrhenius plots can be made, which shows how the formation rate vary with pyrolysis temperature. With this knowledge it is also possible to optimize the pyrolysis temperature in order to minimize the influence of sample size variations and secondary effects. Together with the qualitative information the formation rates of the pyrolysis plots can help to more easily interpret an unknown sample. With an unknown, complex sample it is often beneficial to use fractionated pyrolysis. If the sample is pyrolyzed at a constant temperature, either all of the pyrolysis products from the different substances are found in one pyrogram, or if a too low pyrolysis temperature or too short time is used some sample is left in the pyrolyzer. However, if the same sample is pyrolyzed at different temperatures, one fraction after the other of the sample should be pyrolyzed and give more characteristic pyrograms and less secondary effects. This will result in an easier interpretation.
theory, Arrhenius plot, polymers, characterization, sequential pyrolysis, fractionated pyrolysis