HIPS PS Analytical Differentiation

[MatQual1]

Hello.
Can anyone tell me if there is a way, analytically, to differentiate between HIPS and PS?
Thank-you.

 

[Demon3]

As you may know, HIPS is polystyrene (PS) that contains 20-30 weight% of polybutadiene impact modifier particles. So the way to distinguish them is to look for signs of those particles. There are many ways.

1. The modulus of PS is around 3 GPa, HIPS is significantly lower because the rubber portion essentially has zero stiffness. You could even detect this by placing a weight on a strip of material and comparing how much it bends (primitive flexural modulus test).

2. As for the above, the surface hardness is lower for HIPS and you could detect that with a Shore Hardness meter.

3. FTIR spectrocopy will see the butadiene if there's impact modifier there.

4. NMR spectroscopy would work.

5. Gloss measurements, especially at low angles like 20 degrees can reveal the presence of rubber. Rubber particles lower the gloss.

6. You could dissolve the material e.g. in acetone. The polystyrene will totally dissolve to leave no residue but for the HIPS the PS part will dissolve leaving a sticky residue of the polybutadiene impact modifier.

7. You could heat them in an oven or expose to UV light. The PS will be unchanges and the HIPS will yellow.

8. I'm not sure on this one but you can probably stain HIPS e.g. with iodine which reacts with the polybutadiene but will not stain the PS.

9. Most of all PS is transparent and HIPS is white due to light scattering of the impact modifier particles.

10. DSC will show a glass transition for the impact modifier in HIPS around -80C. You won't see a Tg there for PS.

11. There are more ways...

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com

 

[MatQual1]

Thank-you very much, Dr. DeArmitt.

 

[Demon3]

Best of all you could test the impact resistance. HIPS is good, PS is terrible.

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com

 

[HDS]

Chris could you measure density with a pyconmeter for a nondestructive test?

 

[Demon3]

The density of PS and HIPS are very slightly different so it could work. However, I'd not rely on it because if the pigment levels are different that will cloud the results.

Dr. Chris DeArmitt

Plastics consultant to the Fortune 500:

http://www.phantomplastics.com

Webinars on plastics, fillers & impact modification:

http://www.plastictraining.com

 

[rickfischer51]

Try burning it. ABS will smell like burning rubber because of the butadiene content, and it will burn slowly. PS will lack the burnt rubber smell, and will burn faster. You might want to try it with known samples so you can see and smell the differences. Not as sexy as FTIR or NMR, but cheap and easy to do.

Rick Fischer
Principal Engineer
Argonne National Laboratory