Glass Transition Temperature 1

[stew29681]

Can the glass transition (Tg) of a an adhesive be increased by increasing the cure temperature?

 

[btrueblood]

Ayup. Again, in general. And the thing is, it's all temperature AND time related. I.e., a slightly lower temperature for a longer duration could give higher properties than a higher temperature, shorter duration cure.

 

[stew29681]

Thanks btrueblood, you were most helpful in all your answers.

 

[Compositepro]

Increasing cure time and temperature will increase Tg by increasing degree of cure. But,you cannot go above 100% degree of cure. For most epoxies and bmi's that I'm familiar with you will get about 90% cure after 4 hours at a given temperature. But even after days at one temperature you might be able to get more cure if you raise the temperature. However, there is a maximum Tg for any thermoset and raising temperature or time will not increase Tg above that.

Degree of cure is usually determined by DSC where the energy released during a ramp to cure (2C/min) is measured. Then if you measure a cured sample with the same test it will measure "residual delta H". If that is 10% of what was measured in the first test then you have a 90% degree of cure.