Curing Rate, Dynamic Measurements - METTLER TOLEDO

Curing Rate, Dynamic Measurements

Purpose

To demonstrate the influence of heating on the curing reaction and the maximum reaction rate.

 

Sample

Epoxy resin system consisting of DGEBA and DDM mixed in the stoichiometric ratio of the reactive groups

 

Conditions

Measuring Cell: DSC with IntraCooler

Pan: Aluminum 40 µL, with pierced lid

Sample preparation: Sample masses of 2 to 12mg

DSC measurements: Heating from -40°C to 240°C at three different heating rates.

Atmosphere: Nitrogen, 50ml/min

Interpretation

A comparison of the DSC curves shows that the reaction shifts to higher temperatures at higher heating rates. This is a result of reaction kinetics. The reaction begins above the glass transition temperature, but is still very slow. With increasing temperature, the reaction becomes faster and faster. This is shown by the increasing DSC signal.

 

Evaluation

The reaction enthalpies decrease with increasing heating rates. This can be explained by considering the reaction time. At low heating rates, more time is available for the reactive groups to "diffuse". Crosslinking is therefore more complete, i.e. a larger reaction enthalpy results. This is also apparent from the resulting glass transition temperatures.

 

Conclusion

This location of the reaction peak on the DSC curve depends on the heating rate. This has to do with the kinetics of the reaction, which is the reason why such curves are used for kinetic evaluations. The duration of the isothermal curing reaction at a particular temperature cannot however in practice be estimated from one dynamic DSC measurement.

 

Curing Rate, Dynamic Measurements | Thermal Analysis Application No.HB11 | Application published in METTLER TOLEDO TA Application Handbook Thermosets Volume 1