Modulated Differential Scanning Calorimetry Observation of Physical Ageing in Polymers |
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Authors: | Song M |
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Institution: | (1) IPTME, Loughborough University, Loughborough, LE11 3TU, UK |
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Abstract: | Modulated-temperature differential scanning calorimetry (M-TDSC) is becoming a useful tool in the characterisation of thermal
behaviour of polymers. In this paper, we discuss whether the non-reversing M-TDSC signal can be used, quantitatively and directly,
to study the process of physical ageing in polymers. Difference exists between the values of relaxation enthalpy determined
by using average heat capacity, <C
p>, signal as for conventional DSC and non-reversing heat capacity, C
n
p, signal. When the signal of reversing heat capacity of unaged sample is considered as baseline for <C
p> and C
n
p signals, the difference disappears. It is concluded that non-reversing M-TDSC signal can be used to observe the process of
physical ageing semi-qualitatively and directly. With increasing annealing time, the peak of the imaginary part, C″p, of the complex heat capacity becomes narrow, but peak area changes little. This indicated that C″p is not correlated with relaxation enthalpy. It may be related to entropy change during the modulation. However, the entropy
change is quite small.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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Keywords: | entropy glass transition modulated DSC physical ageing |
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