Thermogravimetric analysis, depolymerization

Thermogravimetric analysis is another way to determine whether PEtG is well end-capped or not. Indeed, a PEtG which is not end-capped or not properly end-capped will not be stable even at 50°C since chain depolymerization could occur, while end-capped PEtG is stable up to 200°C. 

Data of complex thermogravimetric analysis showing that introduction of bis-aroilenbenzimidazole derivatives into PCA shifts temperature of beginning of PCA depolymerization by 10-25 ° C into the region of higher temperatures are given in Table 11. 

Some confusion is found in the literature over the terms used to describe the thermal treatment of polymers depolymerization, cracking, thermolysis, pyrolysis, etc. In this book, we shall use the term pyrolysis to refer to the thermal decomposition of polymeric materials at high temperatures (above 600 °C) whereas, when the degradation takes place at lower temperatures, we shall refer to it mainly as thermal cracking. However, in some cases it is difficult to assign a process to one of these categories, as is the case in thermogravimetric analysis where the temperature is continuously varied. 

A two-step degradation mechanism for pofycaprolactone has been proposed by Persenaire et al. [42], They studied thermal degradation of PCL by high resolution thermogravimetric analysis (TGA) simultaneously coupled with mass spectrometry (MS) arrd Forrrier transform infrared spectrometry (FTIR). Based on evolved gas analysis by both MS and FTIR it was concluded that the first step was a random rupture of polyester chains via cw-elimination reaction which produced H2O, CO2, and 5-hexanoic acid. The second step is an unzipping depolymerization process at the chain ends with hydroxyl end groups to form e-caprolactone (see Fig. 4.2). 

Poly-BFl was found to depolymerize also in the absence of solvents. Thermogravimetric analysis (TGA) showed that poly-BFl in solid state was not... 

A more detailed study of thermal behavior using both differential thermal (DTA) and thermogravimetric (TGA) analysis gave results that indicate a different aspect of thermal stability (Table 7.4). In ordinary PVC, HCl is eliminated at about 300 C, with depolymerization at about 450-460 C. The latter endotherm was found to be unchanged by the presence of monomer, stabilizer, or plasticizer or by irradiation. However, the dehydrochlorination endotherm (Thci) was quite sensitive to all these factors. The addition of plasticizer and stabilizer alone raised irradiation of such controls had no further effect. In the presence of polyfunctional monomer. 

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