80C 90% RH effects on ABS

[TomWehrmeyer]

The problem consists of reducing swell and distortion of ABS case parts when they are exposed to the above condtions for 24 Hrs. I am looking for a plastic that will meet these customers requirements. The plastic is to be injection molded and available in Asia. Being am electronics guy I was naturally drafted into this problem. The thinnest cross section of the current part is 1 mm. Since this part can endure 80 c at ambient RH I was quite suprised the effect that high humidity causes. I assume that this means water is migrating into the part.

 

[Demon3]

I have worked quite a bit on that topic when I was at BASF. The water uptake of ABS depends in particular on how it's made. ABS is not equal, some manufacturers make the product in a way that really sucks in water and results in swelling and warpage.

What ABS are you looking at?

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Demon3]

By the way, I developed a new process which makes ABS that's way less sensitive to water. When submerged in a water bath at 60C the ABS normally swells and sucks in water. Using the new (not yet commercial) process, this was dramatically reduced.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[patprimmer]

80C is getting pretty hot for ABS anyway. I would need to check data to be sure, but some plastics react to heat quicker when exposed to moisture.

Chris

Might SAN be better, or even PP is shrinkage is not a problem or mineral filled PP if shrinkage is a problem. A company I do some work for certainly managed to make a glass bead, glass fibre and mineral filled blend of PP co-polymer that matched GF Noryl shrinkage near enough to be a drop in substitute.

Regards
Pat
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[Pud]

Water @ 80C: mPPO the most cost effective way to go.

H

http://www.tynevalleyplastics.co.uk

 

[Demon3]

High heat ABS would probably be better.

Yes, SAN would be good as it doesn't such in water.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[patprimmer]

Modified PPO is great to hot water as Harry suggests. I may be wrong but I thought it was quite a bit more expensive than ABS. There may be regional differences in relative pricing.

Also, the real price is the cost per GOOD usable moulding rather than the cost per Kg which supports Harrys suggestion.

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

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for site rules

 

[Pud]

mPPO is faster cycling than ABS - should offset increased material cost somewhat.

What's the cost of part failure caused by a choice of marginal ABS in comparison? At least mPPO has a proven record for water pump impellers.

http://www.tynevalleyplastics.co.uk

 

[TomWehrmeyer]

The product is a consumer electronics product. So these parts are for the housing on a DVR. So in normal usage these parts might see 40C and maybe 50% RH when the unit is powered. The 80C and 95% RH comes from a customer requirement for unpowered storage. Is this requirement realistic? I suppose if these units where in the top shipping container on a container ship sail along the equator you might get close.

So if the injection molder injected the ABS at a lower tempature and more pressure the result might be a part that will absorb less moisture?