Pressure / temperature realtionship in polymers

Colnago

Hi, these is possibly a dumb question but...

I know that with regards to gases: (P1*V1)/T1 = (P2*V2)/T2

However does this still apply to polymers in liquid state?

In an injection moulding machine if I increase the pressure will you get an increase in temperature if the volume of material is constant?

Thanks.

Studiot

No it's not a dumb question
No solid and semi solid materials do not obey the gas laws
but yes they will increase in temperature if you pressurise them whilst at the same time confining them.

The ultimate example of this is what happens to rocks at great depth (and pressure) in the earth.

There is I'm sorry to tell you, no simple relationship between temperature and pressure for these materials.

johnbbahm

Safety comment, Plastics need to be VERY dry when heated and used in compression
molding or extrusion. The water vapor does obey the gas law, and will at best create
foamed plastics.

Studiot

Worthwhile comment.