TABLE OF CONTENTS Pyrolysis is simply the breaking of large, complex molecules into smaller fragments by the application of heat. When the heat energy applied to a molecule is greater than the energy of specific bonds in that molecule, those bonds will dissociate in a predictable, reproducible way. The smaller molecules generated in this bond-breaking process can be identified by a number of analytical tools, including gas chromatography and mass spectrometry. Once identified, they help in understanding the structure of the original macromolecule. Thus, a copolymer of isoprene and styrene is readily identified by a pyrogram, whose dominant peaks are isoprene, styrene, and dipentene, a dimer of isoprene.
A good pyrolysis instrument must be able to heat a sample reproducibly, to a preset temperature at a known rate for a specific amount of time. Inability to control any of these variables will result in a pyrogram that cannot be reproduced. If required, the separated pyrolysis products can each be fed into a mass spectrometer to obtain detailed information on pyrolysis product identity (PGC MS (Section 3.8)) or into an NMR spectrometer (PGC NMR spectroscopy) or into a FT-IR spectrometer (Section 3.9).
Gas chromatography instrumentation is discussed in Chapter 5; see also Appendix 1. As examples, the following pyrolyser units, produced by CDS Instruments, are available.
Pyroprobe 1000. This provides complete choice of thermal processing parameters. Pulse pyrolysis is permitted at rates up to 20 C per second to temperatures as high as 1400 C. In addition to...
