Enthalpy relaxation in an epoxy-cycloaliphatic amine resin |
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Authors: | C Ramírez M J Abad J Cano J López P Nogueira L Barral |
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Institution: | Departamento de Física E. U. P. Ferrol Universidad de A Coru?a Avda 19 de Febrero s/n, 15405 Ferrol, Spain e-mail: labpolim@udc.es Tel.: +34-981-337400 Fax: +34-981-337401, ES
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Abstract: | Enthalpy relaxation in a system containing the diglycidyl ether of bisphenol A (DGEBA) resin and a diamine, 1,3-bisaminomethylcyclohexane
(1,3-BAC) as curing agent, has been investigated by differential scanning calorimetry (DSC). Samples fully cured were annealed
at temperature Tg–15 °C for periods of time from 1 h to a maximum of 168 h. The enthalpy relaxation is analyzed by the peak shift method, in
which the sample is heated at 10 °C/min following cooling at various rates through the glass transition region. The key parameters
of structural relaxation determined were the non-linearity parameter x=0.47 ± 0.02, the apparent activation energy Δh*=1264 ± 48 kJ/mol or Δh*/R=152 ± 6 kK and the non-exponentiality parameter β ≈ 0.3. The results, obtained by the same method, were compared with those for other systems based on fully cured DGEBA. The
correlations among these parameters with the peak shift model should be considered with caution. However, the results show
that a correlation between crosslink lengths and the value of Δh* can be considered. The relaxation process for DGEBA/1,3-BAC proves to be highly cooperative.
Received: 28 June 2000 Accepted: 6 September 2000 |
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Keywords: | Enthalpy relaxation Physical aging Epoxy resin Differential scanning calorimetry |
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