Youngs Modulus Of High Impact Polystyerene 1

[krunalacharya]

I am searching for the accurate value of virgin High Impact Polystyrene Material.

Could any one help me please?

 

[Demon3]

The answer is that there is no definitive accurate value for HIPS because different grades of HIPS vary widely. As you may know, HIPS is composed of polystyrene (modulus ~3.25 GPa) filled with microscopic rubber particles (polybutadiene rubber). The rubber lowers the modulus as the rubber is very soft. The amount of rubber varies a lot from grade to grade because although the rubber improved impact resistance, it is not good for some of the other properties and so the best balance depends on the application.

My advice is to either take a value of ~2.25 GPa as typical, or even better find the datasheet for the grade that you are interested in. All such datasheets are available from the manufacturer for example. You will also find the CAMPUS database very useful for finding materials properties as well as

http://www.matweb.com

where you can find huge amounts of materials data free.

 

[krunalacharya]

Thank you Demon,

I am working on Mechanical Properties of HIPS composites. I have one more query regarding this. If I add glass beads to the virgin matrix, effectively the yield strength should decrease. But in my case it increases. I do not know the reason. When I try to analyse, I find that because of the structure of glass beads, they create a week interface and hence the properties decrease.

What do you suggest?

 

[Demon3]

Hello,

You're welcome. You are right, adding glass beads will always decrease the yield strength. Any isortropic (round) filler in any matrix will tend to decrease the yield strength. I have lots of data to show that.

Anisotropic particles (some talcs, mica, glass fibres) increase yield strength for a variety of reasons. Firstly, they have more surface area : volume ratio and so they give better bonding to the matrix. Also they align when you injection mould your test parts and that gives a falsely high yield strength.

Does that help? If not ask me one more time and explain a bit more what you are seeing.

 

[krunalacharya]

This was a real valuable information. Do you have some data to prove this?

I tried to use the Nicolais and Narkis equation and my reading were well compatible to the equation. Are there any more theories support this?

Thank you for your help.

Regards,
Krunal

 

[Demon3]

Hello,

I am happy to have been of service. I have loads of data to support that but I can't show it here I have data on filled polymers for example and also for impact modified polymers including HIPS and ABS. I even give courses on it and I work for one of the world's largest manufacturers of plastics so I am exposed to this stuff daily.

Basically to find the modulus of the mineral filled polymer or the rubber filled polymer the method is the same. The modulus changes linearly with the volume % of particles added. So you just need to know the modulus of the particles you are adding and then you can calculate the modulus for the composite. That only works for isotropic particles though, but the rubber particles are spherical so it works for HIPS and ABS or for polymers filled with CaCO3 for example. For rubber you can probably assume a modulus of zero or near zero.

You are right that the Micolais and Narkis equation can also be applied to this type of situation. There are other equations too. Adding rubber will also lower the yield strength and naturally improve the impact resistance.

 

[RvL04]

Krunal;

Perhaps a silly question, but why don't you just get your actual material tested? I know it costs a few $$, but that will get you by far the most accurate values. I agree completely with Demon3's first reply here in that one formulation varies greatly from the next. That alone is enough reason for me to never use any type of standard data sheet, because the margin of error between those numbers and my actual materials is usually much bigger than I want it to be. So, I would suggest contacting some materials testing lab (like Axel Products, they've given me some great data in the past) and getting one or more formulations of your material tested.

Ron

 

[krunalacharya]

I end this forum here. I have gathered enough information regarding what i need.

Thanks gentlemnen for helping me.

Keep Posting.
Krunal