Glass transition temperature vs Melting Temperature

[fog37]

Hello Forum,

In the context of polymers, I have see two different temperatures being mentioned:

T_g and T_m (T_g is the glass transition temperature and T_m the melting temperature).

Which temperature should be considered for plastic extrusion applications? The melting temperature T_m?

What is T_g used for? what information does it provide? Can T_g be important when plastics are not melted but softened to produce objects with particular shapes? Extrusion, molding seem to always have to melt the polymer...

thanks,
Fog37

 

[wasif]

Hello Forum,

In the context of polymers, I have see two different temperatures being mentioned:

T_g and T_m (T_g is the glass transition temperature and T_m the melting temperature).

Which temperature should be considered for plastic extrusion applications? The melting temperature T_m?

What is T_g used for? what information does it provide? Can T_g be important when plastics are not melted but softened to produce objects with particular shapes? Extrusion, molding seem to always have to melt the polymer...

thanks,
Fog37

Extrusion doesn't really happen at liquid state as it can induce some practical limitations, for metals or non metals an extrusion temperature is determined by optimizing flowability and extrusion forces.

Extrusion temperature lie between recrystallization temperature and melting temperature.

Glass transition temperature is very similar to re-crystallization temperature of metals.