| Abstrakt: |
A series of n-alkanes, CH3-(CH2)nCH3, including polyethylene, crystalline polymers, and crystalline copolymers have been studied by differential scanning calorimetry at very high sensitivity through and above the melting temperature, Tm. A transition designated Tu after KRÜGER et al. is observed at about 1.2 Tm (K) (range 1.10 to 1.42). In low n-alkanes it appears as an endothermic slope change, shifting to an endothermic step change as n exceeds 100. This step change is also characteristic of polymers. Tu is rate sensitive, increasing as the rate of heating increases. Tu by DSC is higher than values reported by KRÜGER et al. from Brillouin scattering and kinematic viscosity. Tu may correspond to the temperature at which persistent structures (smectic, mesomorphic, hetical, etc.) are destroyed thermally. |
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