Polymer Testing 19 (2000) 281–288 Test Apparatus Calorimeter for simultaneous studies of oriented polymers subjected to thermal and mechanical treatments V.L. Velev * , Ch.D. Betchev University of Chemical Technology and Metallurgy, 8, Kliment Ohridski Blvd, 1756 Sofia, Bulgaria Received 6 August 1998; accepted 14 October 1998 Abstract A new type of calorimeter, which enables one to investigate the simultaneous effect of thermal and mechanical treatments on phase transitions in preliminary oriented polymer samples is described. The calorimeter represents a differential type based on the method introduced by Barsky. A clamping device for investigations of the samples studied has been constructed. The experimental data of the calorimetric experiments have been processed by computer and the temperature dependence relationships of T are given. The difference between thermograms without stress and under stress can be observed clearly. It could be concluded that the calorimeter provides a means to investigate the oriented polymeric materials that are simultaneously subjected to mechanical stress during calorimetric experiments.  2000 Elsevier Science Ltd. All rights reserved. 1. Introduction A lot of different calorimeters have been developed for the examination of phase transitions in oriented polymers. Most of them are based on existing industrial models [1,2]. On the other hand, the samples examined by these instruments must be prepared as a powder. Thus it is not possible to investigate the influence of the preliminary molecular orientation on the phase tran- sition of the studied sample. It should be noted that recently a number of so-called deformation calorimeters [3–6] have been proposed. However, only the heat generation as a result of mechan- ical treatment can be measured by these instruments. * Corresponding author. E-mail: betchev@adm1.uctm.edu 0142-9418/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII:S0142-9418(98)00089-0