Complementary Pyrolysis Studies

Pyrolysis kinetics have been carried out on poly-L-lactone salts using TGA linked to various methods such as NMR spectroscopy, gas chromatography and pyrolysis-gas chromatography-mass spectrometry to identify volatile decomposition products. The effect of the end structures on pyrolysis kinetics was examined and the mechanisms of pyrolytic degradation for both polymers identified. 

---

The kinetics of these pyrolysis reactions were followed by several complementary methods under conditions as close to the product studies as possible. The most frequently-used ampule technique14 17) with gc analysis of 5 and the scavenger technique, with chloranil or Koelsch radical as scavenger 18), for very labile compounds 5 were complemented by the DSC method, in which the heat flow under conditions of linear temperature increase is analysed. It proved to be a particularly convenient and reliable technique 18- 21). Rates were followed over a temperature span of at least 40 °C with temperature control of 0.1-0.2 °C. All rate data and activation parameters were subjected to a thorough statistical analysis including statistical weights of errors. The maximum statistical errors in k were 3%, in AH 1 kcal mol-1 in AS 513 e.u. and in AG (at the temperature of measurement) g0.5 kcal mol-1. 

The kinetics of these pyrolysis reactions were followed by several complementary methods under conditions as close to the product studies as possible. The most frequently-used ampule technique with gc analysis of 5 and the scavenger technique,... 

In an early study, now primarily of historical interest, W. Noble et al. dealt with the characterization of adhesives by pyrolysis gas chromatography and IR spectroscopy. The scope of this study, in which 179 commercial products were analyzed and two complementary analytical methods were employed, provides a useful model, though the applicability of the results is limited by the obsolescence of the instrumentation used. 

The complementary nature of IR and MS has been utilised by Duncan [865] in a PyGC-FTIR-MS system with library search capability in the study of the pyrolysis products of polybutadiene and the antioxidant 2,6-di-r-butyl-4-methylphenol. Oguchi et... 

Thermal evolution analysis is an excellent tool for polymer studies complementary to other thermal techniques such as DTA, TG and pyrolysis. Its applications include thermal degradation studies, determination of additives and contaminants, polymer composition and structure identifications. With small variations, the apparatus can also be used for vapour pressure measurements, and for determination of odorous materials in polymer systems. Coupling of TEA to GC for the identification of effluents is practicable and useful. TEA-CT-GC was used for the analysis of volatiles from ABS 10 ppb of styrene but negligible acrylonitrile was detected in the headspace of a typical ABS resin [42]. 

Each MS method presents advantages and disadvantages in being applied in thermal degradation studies (Table 10.3). The choice of the MS technique is of crucial importance to succeed in the reliabihty of the data obtained and to establish the thermal degradation mechanism. In most cases, diverse MS analytical tools should be apphed in investigating the pyrolysis of polymeric systems since the results are often complementary. 

---