Differential Scanning Calorimetry Cure Studies of Tetra‐N‐glycidyldiaminodiphenylmethane Epoxy Resins. Part 1 ‐ Reaction with 4,4′‐Diaminodiphenylsulphone

Rates and extents of cure are determined using differential scanning calorimetry in the isothermal mode over the temperature range 170–220°C, and from d.s.c. scans at various heating rates. The isothermal data are consistent with an autocatalytic mechanism at conversions up to about 20–30%. Data from d.s.c. scans fit a simple kinetic model which indicates that the apparent activation energy (E) for cure increases with increasing conversion, consistent with an increasing degree of diffusion control. At low levels of conversion the isothermal and dynamic data both provide estimates for E of about 70 kJ mol−1. The heat of cure is about 105 kJ mol−1 epoxide, and is constant over a wide range of amine concentration. This indicates that any parallel or competing processes which occur must have the same heat of reaction.