Thermal analysis, characteristics definition

The physical property measured and the corresponding thermal analysis technique are tabulated in Table 1.1 (3) and further elaborated on in Chapter 13. Notice that under the physical property of mass, thermogravimetry (TG), evolved gas detection (EGD), evolved gas analysis (EGA), emanation thermal analysis (ETA), thermoparticulate analysis, and others are included. Similar considerations can be included in the physical proparties of optical characteristics, electrical characteristics, magnetic characteristics, and so on. The definitions of each individual technique are given in the chapter in which they are discussed. A select number of the thermal analysis techniques are summarized in Table 1.2. Each technique is tabulated in terms of the parameter measured, a typical recorded data curve, the instrumentation needed, and the chapter in which it is described. 

The polymers physical aging represents itself the structure and properties change in time and is the reflection of the indicated materials thermodynamically nonequilibriiun nature [61, 62], As a rule, the physical aging results to polymer materials brittleness enhancement and therefore, the ability of structural characteristics in due course prediction is important for the period of estimation of pol5mier products safe exploitation. For cross-linked polymers the quantitative estimation of structure and properties changes in physical aging process was conducted in Refs. [63, 64] within the frameworks of fracture analysis [65] and cluster model of polymers amorphous state structure [7, 66]. The authors of Ref. [67] use the indicated theoretical models for the description of PC physical aging. Besides, for PC behavior closer definition in the indicated process such theoretical notions were drawn as structure quasiequilibrium state [68] and the thermal cluster model [69], which is one from variants of percolation theory. 

Thermal stability of PEI is significantly deteriorated by the use of unpurified monomers. PEI obtained using unpurified dianhydride A possesses poorer molecular-mass characteristics even if all production conditions are maintained (PEI 7, Table 2). Mass-spectrometry analysis of dianhydride A allowed detection of three admixtures bisphenol A, nitrophthalic anhydride (initial monomers for dianhydride A synthesis), and phthalic anhydride. Moreover, PEI thermal stability may be definitely reduced by solvent traces (PEI 8) increased Cf ion content at insulficient washing off of methylene chloride. As known, inorganic admixtures (metal ions) may occur in the polymer both from raw materials (monomers and solvents) and directly from the equipment. In case of iron increments, PEI thermal stability is decreased by its 10-fold exceeding of the permissible level only (PEI 3 compared to PEI 2). 

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