# Relation between thermal expansion and density in Polymers

1. Jul 26, 2015

### sjumesh

Hello all,
Is there any direct relation ship exists between the thermal expansion and density of polymer material (eg. PMMA, Teflon) ?
Like, Lorentz- lorentz law relates directly the refractive index and density of the polymer.
similarly any laws relating (thermal expansion and density of polymer)or ( thermal expansion or refractive index) exists ?

2. Jul 26, 2015

### Staff: Mentor

Yes. The coefficient of volumetric thermal expansion of any material is related to its density by:

$$\alpha=-\frac{1}{\rho}\left(\frac{\partial \rho}{\partial T}\right)_P$$

Chet

3. Jul 26, 2015

### sjumesh

Dear Chestermiller,

At first, thank you for your message.
Yes, i was asking for these equations. And, also is there any relationship between the thermal expansion and refractive index of material.
Any equation relating thermal expansion and refractive index of material.

Can you suggest me any books or materials to study.

regards,
Umesh.S

4. Jul 26, 2015

### Staff: Mentor

I
'M not aware of such a rrlationship, but I'm not an expert. Any text on polymer science should answer your question.

Chet

5. Jul 26, 2015

### sjumesh

Dear Chestermiller,