Stability analysis, molecular fingerprinting

These several examples of TGA mass loss curves have shown how useful this thermal instrument can be in kinetic analysis of thermal stability and in quantifying the amount of low-molecular-mass products in a polymeric material as well as determining the level of components in a copolymer. Even in the case where degradation of a complex blend cannot be carried out quantitatively, it was demonstrated how the TGA fingerprint can be used to check the consistency of the supplier s incoming product. 

Time-of-flight SIMS (Table 32.1) can be used in the determination of the chemical structure and the composition of a surface, and it detects all the elements from hydrogen to uranium (Holmbom and Stenius, 2000). The advantage of SIMS compared to XPS is that with SIMS precise molecular information of polymers can be obtained. Fingerprint spectra can also be found from literature for a series of polymers from low-density polyethylene to polyethyleneterephtalate (PET) (Vickerman, 1989). It is also possible to analyze the molar masses of polymer samples up to 10,000 g/mol (Belu et al., 2003). Several sample types can be analyzed (powders, liquids, and solids) and special pretreatment is not needed. However, the analysis is performed under ultrahigh vacuum, which means that to ensure stability under vacuum conditions membrane samples must be analyzed in their dry state (Belu et al., 2003 Hagenhoff, 1995). 

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