PHASE-ANGLE CORRECTION FOR TMDSC IN THE GLASS-TRANSITION REGION

Temperature-modulated DSC (TMDSC) allows the determination of frequenc y (time) dependent heat capacities. If heat capacity is frequency depe ndent, for example, in the glass-transition region, one get a phase an gle between heating rate and heat-flow rate which is related to materi al intrinsic properties. Because heat does not propagate but flows, th e time-consuming heat transfer into the sample yields an additional ph ase angle. This phase angle has to be taken into account if one wants to calculate the imaginary part of the complex heat capacity of the sa mple from the measured phase angle. The heat transfer related phase an gle depends on frequency heat capacity and heat conductance. In the ca se of glass-transition, heat capacity and heat conductance may change in the respective temperature interval. A correction for the correspon ding phase angle is suggested. (C) 1997 Elsevier Science B.V.