Unzipping poly methyl methacrylate
Some synthetic polymers, including the methacrylates, simply unzip at pyrolysis temperatures, generating mostly monomer. This is the case for poly methyl methacrylate, shown in Figure 4. Instead of a series of increasingly longer oligomers, the chromatogram shows a large peak for monomer and little else. This behavior is seen in copolymers involving the methyl methacrylate monomer as well as in the pure homopolymer, and acrylic copolymers, in general, produce monomer peaks for each of the monomers used in the formulation.
Side-group elimination poly vinyl chloride
In the polymers discussed above, the weakest bonds are those holding the chain together, so pyrolysis produces either fragmentation to smaller oligomeric units or unzipping all the way to monomer. For some polymers, however, the groups attached to the side of the chain are held by bonds which are weaker than the bonds connecting the chain. In such cases, the side groups are stripped off from the chain before it is broken into smaller pieces, so no monomer or higher oligomers are seen. This is the case for some vinyl polymers, including poly vinyl chloride3, poly vinylidine chloride and poly vinyl acetate. In PVC, the carbon-chlorine bond is the weakest, so a chlorine-free radical is generated at relatively low temperatures. This chlorine removes a hydrogen from the polymer, making HCl gas, and leaving behind a highly unsaturated chain. The chain then degrades to produce aromatics, so the pyrolysis products from PVC include HCl, benzene, toluene and other aromatics, even naphthalene, as seen in Figure 6 (Page 4).
Interfacing a CDS Pyroprobe 2500 Pyrolysis Autosampler to a PerkinElmer Clarus 500 GC/MS is a simple way to e