High SG thermoplastic rubber

[espresso51]

Hi,
I have a client who is wanting us to mould parts in a Thermoplastic Rubber with an S.G. of 3.2 (and other parts with even higher SG's).
I have a compounder nearby who can compound the material for me, but he only has experience with Barium Sulphate that will give us an sg of about 3.
any suggestions as to what fillers are available that
1) have an sg of 5,6,10??? to give us the higher densities?
2) can be run through an extruder and injection moulding machine without damaging the machines?
3) Reasonable price and freely available?
Thanks.

 

[Pud]

The stuff that's put in to make rubber magnets is pretty dense. I believe it's iron oxide (magnetite)?
Alternatives are tungsten powder, iron powder, etc.

H

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[espresso51]

I don't think my moulding machine would like this though.

 

[Pud]

Why not? Screws and barrels are like tyres and brakes on cars - consumable wear items. Just price the job to include wear and tear.
It's not actually that abrasive - there are no "ends" as there are with glass fibre filled stuff.
There are millions of magnets moulded each year - there is a compounder in the UK who does nothing else but magnetic materials. Does very nicely I believe...
Tungsten powder filled nylon is used to make bullets for special forces (Indoor use. Go though bodies but not through walls).

H

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

 

[patprimmer]

Bronze filled nylon also makes a nice bullet.

Bronze will certainly get the SG you want.

The more dense the filler the less you need so the less the impact on other properties.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Demon3]

There are alternatives but I agree that magnetite (specific density 5.0 g/cm3) is a good choice. Leading supplier is Minelco.

Also, be careful when shooting for a certain target density. 99/100 people get the calculation wrong. The density of the composite depends linearly on the volume % of each ingredient not the weight %.

Use this for example:

http://www.netcomposites.com/calculators/volume-weight-fractions

Chris DeArmitt - PhD FRSC CChem
Plastic & Additives Webinars
Instant Downloads & Inexpensive

http://www.plastictraining.com

 

[Demon3]

Assuming the rubber has a density of 1.0 and the Magnetite 5.0 you need 83 weight% filler to get a composite with a density of 3.0 g/cm3.

Chris DeArmitt - PhD FRSC CChem
Plastic & Additives Webinars
Instant Downloads & Inexpensive

http://www.plastictraining.com

 

[espresso51]

"Assuming the rubber has a density of 1.0 and the Magnetite 5.0 you need 83 weight% filler to get a composite with a density of 3.0 g/cm3."
I can't see how one could get such a high filler loading?
I need to find a filler with an sg of about 12.

 

[patprimmer]

It is only about 17% by volume so it should wet out

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[Demon3]

Assuming spheres you can get loadings approaching 60 weight %.

For 83 weight% Magnetite you have 50 volume % of filler and 50 of resin so that will work. See for yourself using that online calculator I linked to.

If you need higher density filler try iron (8 g/cm3) or tungsten (19 g/cm3).

Chris DeArmitt - PhD FRSC CChem
Plastic & Additives Webinars
Instant Downloads & Inexpensive

http://www.plastictraining.com