Details of the Heat Capacity of the Rotator Phase of Pure n-Paraffin Crystal. Mesurement by AC Calorimetry for Heptacosane(n-C27H56).:Mesurement by AC Calorimetry for Heptacosane (n-C27H56)

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Temperature dependence and time dependences of the heat capacity of n-paraffin crystal (C27H56) in the rotator phase were studied by AC calorimetry. High purity material (99.9%) was used as the sample to avoid the large impurity effects to the phase transition behavior. Measurement during temperature scanning at 0.5K/min showed existence of motion in the rotator phase with the relaxation time about 0.3sec. Time dependence of the heat capacity at constant temperature in the rotator phase showed that the heat capacity changed with time very slowly. After the relaxation for twelve hous in the ratotar phase the sample was cooled down to the low temperature phase then heated up to the liquid phase. Temperature dependence of the heat capacity on the cooling and the heating processes showed that the relaxed state reached at temperatures higher than 329.9K was distinct from that reached at temperatures lower than 329.5K. It was found that there were two stable phases in the temperature region of the rotator phase. A model to explain the experimental results was proposed.
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