Pyrograms of Various Polymers

List of pyrograms of various poiymers List of Pyrograms of Various Polymers (continued)... 

By now, a wealth of experimental data on the Py—GC of polymers has been accumulated, suggesting that this method can be applied extensively for identification of various polymer systems. To identify a polymer by the fingerprint method, its pyrogram is compared with those of known substances and, on the basis of this comparison, the spectrum of the test sample is identified. A sample can be identified only if a pyrogram of the substance of interest is avaQable in advance. The method is marked by high resolution. A... 

Py-GC is sensitive to such structural features of the polymer chain as the mutual arrangement of the substituents. Various pyrograms of polypropylenes of different stereoregularity (atactic and isotactic) have been obtained [148]. 

The THM reaction linked to GC, GC/mass spectrometry (MS), and MS has been successfully applied to the chemical characterization of a number of synthetic and natural products, including resins, lipids, waxes, wood products, soil sediments, and microorganisms. This technique is also very effective for the detailed characterization of the synthetic polymeric materials, especially the condensation polymers, such as polyesters and polycarbonates, because many simplified pyrograms are usually obtained that consist of peaks of methyl derivatives from the constituents of the polymer samples almost quantitatively. In this chapter, the instrumental and methodological aspects of Py-GC in the presence of the organic alkali are briefly described, and then some typical applications to the precise compositional analyses and microstructural elucidation inclusive of the intractable cross-linking structures for various condensation type polymeric materials are discussed. 

Figure 5.13 shows the pyrograms of EPDM with various ethylene/propylene (E/P) compositions and a constant ENB content (7.1 wt%). The fact that linear olefin peaks (LE) are observed up to C20 suggests that more than the heptad of the ethylene sequence (-CH2-CH)t-) exists in the polymer chain, even though both sides of the terminal groups in linear olefins incorporate propylene units (see Scheme 1)... 

PyGC-MS enables differentiation between various brominated flame retardants. Pyrograms of the reference materials (pure FRs) need to be compared with that of the sample to be examined in order to identify the flame retardant class. Selection of the pyrolysis temperature is most important. A compromise between mobilisation of the flame retardants and minimisation of thermal reaction products has to be found. Flame retardants were identified in EPR/TBBA, ABS/TBBA, PBT/TBBA, PP/PBDE, HIPS/PBB, using an optimised pyrolysis temperature (430°C) for these systems [791]. PyGC-MS was also used for polymer and additive (FR) characterisation of a Japanese TV cabinet [792]. Figure 2.36 shows the additive fragments isolated, together with a proposed (sub)structure, sufficient to identify the flame retardant as tetrabromobisphenol-5 -bis-(2,3-dibromopropylether) (TBBP-S) on the basis of patent search. 

The pyrograms obtained on these various polymers are shown in Figures 10.1(a) and 10.1b (n-Cg peak taken as reference). These pyrograms show marked differences which can be attributed to differences in short chain branching. The small amount of branching in Marlex 5003 and Ziegler polyethylenes is reflected only in the somewhat larger iso-alkane peaks, whereas the n-alkane pattern is practically the... 

In the early stage of Py-GC, significant interlaboratory discrepancies between pyrolysis data (pyrograms) were reported even for the same polymer types. This was mainly because of a diversity of pyrolysis devices operated under varied conditions. Owing to continued improvement of pyrolyzers and fundamental studies to control the operating conditions and obtain reproducible and characteristic degradation of the studied materials, most of the commercially available pyrolyzers now have made the interlaboratory discrepancies a minor problem. Now, various flash filament-, furnace-, and Curie-point type pyrolyzers are utilized for both Py-MS and Py-GC. 

Other polymer properties, such as tacticity, can be studied by Py-GC. One example was the characterization of methyl methacrylate (MMA) sequences in the copolymers of MMA and various acrylates and their cross-linked polymers. Tacticity was determined by Py-GC based on the relative peak intensities of the diastereomeric MMA tetra-mers in the pyrograms. 

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