Estimating heat transfer bias of kinetic measurement for polymers by differential scanning calorimetry with isothermal mode

The non-uniformity of temperatures in the DSC sample, and the subsequent difference between mean sample temperature and measured one (in the support of the crucible) are identified as the main source of bias for the isothermal mode determination of kinetic characteristics by differential scanning calorimetry. Chemical reactions under consideration are these with important heat effects into thermal insulators, as for example the reticulation of polymeric materials. By introducing an analytical model of heat transfer in DSC reactive samples, we have performed an estimation for the upper limit of the maximal size of samples which corresponds to a given relative error of the reaction rate, as measured by isothermal DSC calorimetry. For example, with a 5% error and flat samples, we have found admissible sample thicknesses which decrease with temperature and are between 1.9 and 3.1 mm for the sulphur vulcanisation of a natural rubber and between 0.6 and 1.1 mm for the reticulation of a prepolymerized epoxy resin. (C) 2003 Editions scientifiques et medicales Elsevier SAS. Tous droits reserves.