Why do we need to consider the Tg when selecting an epoxy?
QUESTION:
Why do we need to consider the Tg when selecting an epoxy?
ANSWER:
One reason to consider the Tg is in selecting an epoxy that is appropriate for an application. For an application requiring a flexible epoxy, a low Tg, something below 0°C is appropriate. In most cases this would actually not be an epoxy; more likely a silicone material. But either way, a silicone or flexible epoxy has the ability to move and absorb stress – as in an application where the epoxy acts as a sealant, or provides shock and vibration protection. Other applications may require the strongest physical properties of the epoxy; in which case a high Tg (relative to the operating range of the application) would be appropriate. This would utilize the high strength, compression, tension, etc. properties of the epoxy.
Another reason to consider the Tg is that the thermal coefficient of expansion (TCE or CTE) is smaller at temperatures below the Tg, and larger for temperatures above the Tg – sometimes quite.
Depending on the application this could impact the performance of a device. If this is the case, then it is important to select an epoxy with a Tg that is entirely above or below the normal operating temperature range of the device.
The bottom line on Tg? The Tg provides important information about the nature of any given epoxy at its service temperature.
READ THE FULL BLOG ARTICLE HERE: The Glass Transition in Epoxies
