How to spec Polystyrene Sheet

[erabinowitz3]

Hi, We're looking to use a polystyrene sheet, thin, similar to a credit card (I know most CC's are PVC)...

The material must have certain properties, and we've recently been made aware that its possible for a mfr to aerate or "foam" polystyrene sheets to reduce material costs. But in turn it will change the material properties.

To try to reduce this, I’ve been advised that we need to add a note to our drawing with the effect "No foam polystyrene"...

Is this the right way to call this out? I've found foam polystyrene being spec'd out per its density...do i want to specify the min density, as the aerating will only make it less dense?

Thanks

 

[erabinowitz3]

i found a spec sheet for polysty, and it listed the specific gravity...which should be unitless, although they lsit it as g/cm3....is this the best way? anyone know the tolerences for specific gravity? it didn't say in the spartech spec sheet

 

[CoryPad]

Yes, you can specify specific gravity (which is unitless). The spec sheet you read provided mass density.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Demon3]

What is the application? A thin sheet of polystyrene will be brittle and not perform well in many applications.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[erabinowitz3]

"What is the application? A thin sheet of polystyrene will be brittle and not perform well in many applications. "

The application is similar to that of a credit card with tabs that break off at score lines, or punch out of a larger card (like a sim card)...but no circuits... legally i can't tell you any more then that

"The spec sheet you read provided mass density."

have you worked with spartech plastics before? are you guessing that instead of listing the wrong units under "specific gravity," instead they listed the wrong test/specification title, and the units are correct?

 

[Demon3]

I would certainly not make any kind of credit card from polystyrene. It is way too brittle with a very low elongation to break or flex to break. On top of that it is sensitive to any kind of oils or cleaning fluids. There are much better alternatives.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[Demon3]

If you can list some of the requirements then the people here can suggest some other materials.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell

 

[CoryPad]

I have not worked with Spartech before. Mass density is mass divided by volume, with typical units g cm^-3 or kg m^-3. Specific gravity is mass density of object divided by mass density of water, so they are intimately related and sometimes erroneously switched.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[8Y8sailor]

I've produced HIPS sheet for a very similar sounding application, you'll probably wind up needing a blend of HIPS and GPPS to get the right amount break while retaining sufficient flexibility.

DOW, Huntsman, Basf all have Data sheets on their sites which will give you some generic figures to work from.

Steve

 

[Demon3]

Another trick to overcome brittleness of PS is to blend in a few weight % of a compatible SBS such as Styroflex.

There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell