Just wondering if someone can put me straight on this.
I’ve been looking at the filament specifications for BL PET-CF & PAHT-CF.
I’m looking at what temperatures they begin to warp at.
I started looking at the Glass Transition Temperatures. Now Google tells me that Glass Transition Temperatures means “indicates when the material starts to soften and lose its solid structure.”
Now on the PETG-CF spec it has the Glass Transition Temperatures as 75°C and PAHT-CF as 70°C.
The Heat Deflection Temperature for these is way higher than the Glass Transition Temperatures.
The Tg describes the temperature at which vitrification or glassification begins, i.e when “freezing” of the movements of chain segments (kinetic units) takes place, whereas the HDT is a macroscopic measure of the “stiffness” of a material when the temperature increases. For unfilled systems, the two properties are often closely related (see Figure below). However, fillers, and reinforcements will greatly change the HDT since reinforcements make the material stiffer whereas the Tg is not noticeably affected by these ingredients since it describes the softening of the polymeric portion. Infact, the HDT of filled and unfilled plastics can vary a lot, depending on the filler / fiber content and type. Both properties are equally affected by plasticizers.
So, the fact that you’re looking at CF-filled filaments significantly affects the HDT without measurably changing the Tg (glass transition temperature).
I think both may be correct, but it is not very clear. The Glass Transition Temperature (Tg) reported is likely when it is unannealed and the other properties are after annealing. That is, you can only get better thermal performance if you anneal. That is my best guess.
