ABSTRACT
Designations of the most important transitions which polymers display are illustrated in Table 8.1 as presented by Van Krevelen [S2].
8.3 DETECTION There are a number of techniques that are used to detect
transitions in polymers. The principal techniques of interest are: thermo-mechanical analysis (TMA), dynamic mechanical analysis (DMA), dielectric energy absorption, nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSc). TMA detects discontinuities in the coefficient of thermal expansion while DMA measures the viscoelastic response of a material to periodic forces allowing changes in the modulus and tan 6 to be followed and
Detection 259
DSc measures changes in heat capacity or enthalpy of fusion, as discussed in Chapter 7. The simplest and therefore the most prevalent techniques used are that of DSc and DMA. These two techniques, or a variation of DMA called DMTA, which is simply dynamic mechanical thermal analysis, allow the viscoelastic behavior of a polymer to be followed as a function of temperature. These techniques often provide definitive results and permit informed interpretation of structure-property relationships of the polymer, based on the transitions occurring.
