Temperature modulated differential scanning calorimetry (TMDSC) in the region of phase transitions. Part 2: Some specific results from polymers

By means of four different examples (pressure crystallised, gel crystallise d, nascent and highly stretched polyethylenes (PEs)) it is shown that tempe rature modulated DSC offers advantages against common DSC. It is possible t o see dynamic processes inside the sample during melting. This way we found (i) that during melting of high pressure crystallised PE the so-called alp ha(2)-process (known from DMA) takes place, (ii) the lamellae doubling in g el crystallised UHMWPE can be seen in TMDSC signals, though no balance heat flow rate is visible in the common DSC, (iii) the same is true for the rec rystallisation in nascent and highly stretched PE many degrees before the m elting peak appears. To separate these results from the measured curves the knowledge of the heat transport into and within the sample is needed. A si mple low pass filter model has proved its worth for this purpose. (C) 1999 Elsevier Science B.V. All rights reserved.