Plastic weathering
Plastic weathering
(OP)
I am working on a 2-piece weatherproof enclosure for electronics that control a streetlight. The enclosure sits on top of the streetlight and so the top piece (cap) will be exposed to weather (UV, rain, wind, temperature -40C to +70C) and impact (hail) for extended periods (10-20 years). The top piece is snap-fit onto the base so it must also have a little flexibility. So I need something UL-746C f1 outdoor rated and UL-94 HB fire rated that meets the above criteria...and of course cost is always an issue.
I am considering PC stabilized with HALS and colored with TiO2 (light color to minimize the thermal rise that would be hard on the electronics inside) or Carbon Black. Other options might be a PC-ABS blend for lower cost and better cold-weather characteristics. Are these the best choices? Should I be considering PP or PA?
Any experience with materials, thicknesses, and stabilizers for long outdoor life would be much appreciated. Thanks!
I am considering PC stabilized with HALS and colored with TiO2 (light color to minimize the thermal rise that would be hard on the electronics inside) or Carbon Black. Other options might be a PC-ABS blend for lower cost and better cold-weather characteristics. Are these the best choices? Should I be considering PP or PA?
Any experience with materials, thicknesses, and stabilizers for long outdoor life would be much appreciated. Thanks!





RE: Plastic weathering
RE: Plastic weathering
PP is very poor in all qualities your after except price and snap fit. It is crumby to UV, FR and cold impact. The addive packages you need and the interaction between various packages is problematic to say the least
A polyester/urethane block copolymer like Hytrel will be expensive, but might hit all your goals without a huge additive package
Also for nylons, the additives to fix some problems will exacerbate others.
Cold impact FR, UV combo is the tricky bit
Regards
Pat
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RE: Plastic weathering
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www.tynevalleyplastics.co.uk
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RE: Plastic weathering
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RE: Plastic weathering
RE: Plastic weathering
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RE: Plastic weathering
PC remains a top contender, but I've looked into some of the materials discussed and am researching them further; any thoughts on relative costs would be appreciated. I've listed the main concerns and relevant links below:
PVC: an interesting choice: low cost with many UL 746C formulations. My main concerns is low-temperature impact resistance which falls off drastically below 10C. Maybe a fiber reinforced PVC?
http://www.matbase.com/material/polymers/commodity...
(see here: http://www.madisongroup.com/services/failure/casep...).
PUR: Better at low temperature, but high cost and concerns with hydrolytic degradation (especially for polyester polyurethanes).
http://www.matbase.com/material/polymers/thermoset...
FR PBT: An interesting option...I need to look into this more. Low temperature is an issue with PBT, but the FR seems to help.
http://www.matbase.com/material/polymers/engineeri...
http://www.matbase.com/material/polymers/reinforce...
RE: Plastic weathering
Most PU is fairly poor to UV and its very rubbery. It produces cyanide gas when it burns if that matters.
PBT will have cold impact issues, but is very easily made FR and UV resitant. Toughened grades are available that can also still have good UV and FR with reasonable additive packages.
The polyester block elastomers like Hytrel are basically PBT with some PU incorperated to improve impact.
Regards
Pat
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RE: Plastic weathering
RE: Plastic weathering
from my experience I would use a blend of ABS/ASA.
They use ASA for all kind of outdoor applications.
The problem will be that you get the blend only in sheet stock, so the only way to form it will be thermoforming.
Let me know if you would like to have more information's about the material.
RE: Plastic weathering
You can also get PC/ASA blends, but once again, why. What advantage would it bring to PC
Regards
Pat
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RE: Plastic weathering
Regards
Pat
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RE: Plastic weathering
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RE: Plastic weathering
To answer a few questions (and ask a few more):
- The target process is injection molding
- The bottom piece has has brass electrical contacts molded/pressed in that will be soldered to the internal electronics; the soldering process will make the pins very hot so I need a polymer with a high melting point...I am considering PA6-GF30 or PC-GF30.
- Also, the electronics include a wireless transceiver so Carbon Black is out as a UV stabilizer/pigment because it absorbs RF energy.
RE: Plastic weathering
Any other surprises?
UV stabilised nylons 6 and 6.6 are extensively used in street light housings here where we have extended exposure to the highest UV in the world and they must also pass the Pelican Test.
6.6 is normally used if the housing gets very hot short term. 6 is better if it gets fairly hot long term, but both types are used a lot.
Regards
Pat
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RE: Plastic weathering
dalbert,
I found this comment interesting and I wonder if you have any further comments or information on materials that are suitable for housing electronics for RF transmission?
Thanks
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