HALS & UV Absorber in Opaque/Rigid Polymer?

[Berkelium]

Greetings all,

I've got a few questions, so tihs might be a bit lengthy.

Background info:
I'm working on replacing a product currently made from fiberglass with some sort of polymer. It's a utility-scale resistor housing-a tube with flanged ends. It would need to maintain its mechanical, thermal, and electrical properties up to 30 years in the sun.

Question:
Are UV absorbers, hindered amine light stabilizers (HALS), and antioxidants useful in rigid plastics like rigid PVC, or are they only valuable in flexible/thin plastic products? PVC has the material properties that I need, but I'm looking for a way for it to retain those properties for 30 years in the sun...

Thanks in advance for your replies.

 

[patprimmer]

I don't believe PVC will last that long.

PMMA or PTFE would be your best choices if their physicals are OK.

PET with plenty of fine dispersed carbon black and a good UV stabiliser package may suffice. The carbon black protects the matrix, but not the surface. The surface will erode and micro cracks will form and may propagate. Carbon black is permanent and has a blocking action not a stabilising action.

UV stabilisers can protect the surface, but they are sacrificial and will be consumed over time.

Can you use the best stabilised PVC you can get then paint it with a UV opaque paint and maintain the paint.

Regards
Pat
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[Demon3]

Stabilizers for PVC are completely different to those for other polymers like PE, PP, PET etc. so no, HALS won't work.

As Pat said, you need 1-2 % carbon black and other stabilizers in the system.

This formulation is in a critical application so the best guess of even the best expert is not good enough. You will need to contact a stabilizers expert who can advise and who can check the weatherability with Xenotest and Weatherometer.

The best such place I know is called Stabilization Technologies (

http://www.stabilization-technologies.com)

. Ask to speak to Joe Webster.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[patprimmer]

Chris is absolutely correct.

When I said best possible stabiliser system, I should have said best possible stabiliser system formulated specifically for that polymer. It does vary from polymer to polymer.

Regards
Pat
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[Berkelium]

Thanks for the replies. I do need something opaque, so regular PMMA or PTFE wont work. If I add carbon black to either of those, I'd guess they'll have issues with uv damage as well. I am considering painting the PVC (or whichever polymer I use), but this needs to be almost zero maintenance meaning no repainting for many, many years. Demon3 thanks for the reference-I may just look into that.

Perhaps a polymer is out of the question for this application, but I'll go look into the possibility of a transparent polymer. The issue then would be uv degradation of the resistors themselves which are ceramic that I think are jacketed in a composite...

 

[Demon3]

Carbon black blocks virtually all of the UV and can be added to most polymers no problem.

The only issue is that carbon black can't protect the very surface as the UV hits that before it gets to the carbon black.

Chris DeArmitt PhD FRSC CChem

http://www.phantomplastics.com

Consultant to the plastics industry

 

[Berkelium]

Well, we've got these paints that we mix and put on the surface of the current product, and we're going to check the old installations to see how it's holding up. It's Devthane 379 and Devthan 379UVA, and if it adheres as well to the PVC as it does fiberglass then we'll be in good shape I think. Combined with whatever UV package the PVC manufacturer can give us, I think we'll be in good shape.

If that doesn't work, we may actually go with either of those two transparent polymers because the resistors inside are ceramic.

Thanks guys for your input.