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Glass Transition Temperature 1

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stew29681

Materials
May 21, 2009
4
Can the glass transition (Tg) of a an adhesive be increased by increasing the cure temperature?
 
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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.
 
Thanks btrueblood, you were most helpful in all your answers.
 
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.

 
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