The glass transition temperature (Tg) is somewhat of a misnomer, as it is actually a range of a few degrees Celsius over which a polymeric material transitions from a glassy (rigid) to elastomeric (rubbery) state. The Tg is typically reported as the median of that range of temperatures. The Tg can be measured by differential scanning calorimetry (DSC), thermo mechanical analysis (TMA), or dynamic mechanical analysis (DMA).
The Tg of a material helps to define its mechanical properties. Silicones, for example, all have a Tg around -100°C. For typical operating temperatures (-40 to +200°C), the silicone will always appear soft and flexible, because it is always operating above its Tg.
Other chemistries have variable Tg. Often, the Tg of these materials is determined by the temperature at which the material is cured. The higher the cure temperature, the higher the Tg. For applications that require consistent mechanical properties over the entire operating temperature range, having a Tg outside that the operating temperature range is imperative.
Our range of structural adhesives utilizes acrylic, epoxy and urethane chemistries - providing various options in terms of cure temperatures, operating temperature ranges, mechanical properties and Tg.