The Use of Scanning Transitiometry to Investigate Thermodynamic Properties of Polymeric Systems over Extended T and p Ranges

Scanning transitiometry is a newly developed technique in which one of the independent variables (p, V, or T) is scanned in the working cell of a very sensitive calorimeter while the other independent variable is kept constant. The change of the dependent variable is recorded simultaneously with the thermal effect associated with the process or the system under investigation. In the case of non-reacting systems which remain in a homogeneous state, both the mechanical and thermal outputs thus obtained give straightforward access to pairs of thermomechanical coefficients: ap and oT, bV and oT, Cp and ap, CV and bV, depending on the pair of selected independent variables. When the system or the material sample goes through a chemical reaction or a phase change, the recorded information yields the corresponding heat and pVT characteristics. The working cell may also house an optical fiber probe for spectrophotometric in situ readings from UV to NIR, as well as injection and stirring devices permitting investigation of reacting systems. The actual operating ranges of current scanning transitiometers are 173 K