Pressure / temperature realtionship in polymers

AI Thread Summary
The gas law relationship does not apply to solid and semi-solid materials like polymers. In injection molding, increasing pressure can lead to a temperature rise if the volume remains constant. However, there is no straightforward relationship between temperature and pressure for these materials. It is crucial to ensure that plastics are very dry during heating and processing to avoid issues like foamed plastics. Understanding these principles is essential for safe and effective use of polymers in manufacturing.
Colnago
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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.
 
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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.
 
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.
 
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

Worthwhile comment.
 

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