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Keywords:

  • diglycidyl ether of bisphenol–A (DGEBA);
  • pyromellitic dianhydride (PMDA);
  • imidazole;
  • curing;
  • thermal stability

Abstract

The curing behaviour of DGEBA was investigated by differential scanning calorimetry in the presence of varying amounts of PMDA. The molar ratio of DGEBA : PMDA was varied as 1 : 0.8, 1 : 1, 1 : 1.5, 1 : 2.0, and 1 : 2.5. The heat of polymerization (ΔH) was found to be maximum at a molar ratio of 1 : 0.8 (DGEBA : PMDA). To study the effect of imidazole content on the curing behaviour, varying amounts of imidazole, i.e., 0.1, 0.15, 0.2, and 0.3% (w/w) were used keeping the ratio of DGEBA : PMDA (1 : 0.8) constant. A broad exotherm was observed in all the samples. A significant decrease in the peak exotherm was observed when 0.1% imidazole was used. Further increase in the imidazole concentration up to 0.2% resulted in a marginal decrease in the peak exotherm temperature. Thermal stability of epoxy resin, cured isothermally, was evaluated by recording thermogravimetric traces in nitrogen atmosphere. The percent char yield was highest in case of resin sample, IP1-30 (i.e., DGEBA (1 mole) cured using 0.8 mole of PMDA in the presence of 0.3 (w/w) of imidazole). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007