The different transitions involved in the curing reaction of a commercial epoxy thermoset called Sikadur®-30 which consists mainly of diglycidyl ether of bisphenol A (DGEBA) and a trimethylhexane diamine was studied to develop a time-temperature-transformation (TTT) isothermal cure diagram for this system. The TTT diagram is expected to enhance the cure cycles for different cure regimes which will allow back calculation of cure time for an isothermal cure temperature. This is not given in the manufacturer's data sheet. Therefore this allows better flexibility in using the epoxy system, which is often needed when assembling civil engineering structures under changing outdoor conditions. The gel times were identified using oscillatory rheological measurements. Vitrification times were determined through differential scanning calorimetry (DSC) studies. Glass transition temperatures of the unreacted system (Tg0) and fully reacted system (Tg) were found to be - 48 0C and 69 0C respectively. For a known isothermal cure temperature, the occurrences of gelation and vitrification against time provides important information in structural applications. Specifically the gelation curve provides maximum pot life at various isothermal cure conditions which enables optimisation of operations and handling of epoxy system at preceding environmental conditions. As the vitrification is the point at which the reaction rate is severely retarded due to the change in reaction mechanism from kinetically controlled to diffusion controlled, this information enables users to understand the capacity of the adhesive as it also implies that the system has reached a glass transition temperature equal to the cure temperature. Therefore the TTT diagram allows optimised operations and handling of an epoxy system on site allowing users the flexibility to adapt to varying environmental conditions or practical constraints.
|Publication status||Published - 2019|
|Event||22nd International Conference on Composite Materials, ICCM 2019 - Melbourne, Australia|
Duration: 11 Aug 2019 → 16 Aug 2019
|Conference||22nd International Conference on Composite Materials, ICCM 2019|
|Period||11/08/19 → 16/08/19|
- Cure kinetics
- Time-temperature-transformation diagram