Time dependence of the complex heat capacity at the melting temperature of polyethylene crystals

Time dependence of the complex heat capacity of polyethylene crystals was measured at several temperatures between 80 and 130°C using light heating modulated temperature DSC. Time dependence could be expressed as a sum of fast and slow components. The fast component had the complex value and decayed within a few minutes. On the other hand, the slow component had the real value and decreased much more slowly towards a finite value. The fast and slow components were attributed to melting and ordering of the crystal, respectively. Time dependence was significant at temperatures in the melting peak of the total heat flow (123°C and higher). However, even at the lowest temperature very small fast component was observed. This suggested that a very small amount of the crystal melted at this temperature.