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Old 05-23-2012, 10:25 AM   #21 (permalink)
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Quote:
Originally Posted by ecomodded View Post
I was told by a plastic welder who manufactures custom items for commercial and marine use that the black PVC and polyethylene last outdoors in the sun and that the white PVC & poly deteriorated quickly by the penetration of the sunlight threw the white color damaging the plastic,
causing it to be brittle and break easily.
I wonder if the white paints condition, not the color, is more subjected to sunlight damage by its light passing white pigment.

It dawned on me that NASA makes everything white so they can find it again !
or
could be "we never get to "SEE" the black stealth stuff"
White pigment doesn't pass light. it reflects light. If it passed light, it would be called translucent.

There are several ways to impart UV resistance to PVC and polyethylene. The cheapest way is to add carbon black to the plastic. Carbon black absorbs UV and converts it to heat. A more expensive way to protect from UV is to add titanium dioxide to the plastic. Titanium dioxide (also used in sunscreen lotion), reflects the UV, but doesn't provide quite as much UV protection in plastics as carbon black, since the UV can do damage on its way in and on its reflected way back out of the plastic. A third way that can be used to protect polyethylene is to cross link its polyethylene chains, which is how they get the clear greenhouse films to last 4+ years in the sun.

Most of what NASA sends out of earth orbit isn't ever coming back, so they're not expecting to have to try to visually find it again. So that's not the reason they are white.

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Old 05-23-2012, 02:00 PM   #22 (permalink)
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Quote:
Originally Posted by basjoos View Post
White pigment doesn't pass light. it reflects light. If it passed light, it would be called translucent.
Depends. A white substance may reflect from the surface, or (as with some plastics) the light may penetrate some distance before reflecting.

There's also the question of what "color" the white is in the UV spectrum. Consider flowers: bees see in the ultraviolet, so a flower that appears to be white or solid color to human vision often looks much different in UV. See for instance Flowers in Ultra-Violet
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Old 06-04-2012, 03:25 PM   #23 (permalink)
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I've been thinking about it, but this thread pushed me over the edge.
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Old 06-04-2012, 09:00 PM   #24 (permalink)
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I'm just waiting for California to ban all non-white cars in a bid to single-handedly solve global warming.

-

I'd author the bill myself, if anyone is interested in supporting it...
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Old 03-14-2013, 10:41 PM   #25 (permalink)
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Has anyone considered gluing a sheet of Mylar to the roof?
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Old 03-15-2013, 01:24 AM   #26 (permalink)
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Quote:
Originally Posted by shovel View Post
I've always been a fan of white roofs for this reason (even reducing duty cycle of factory equipped "overpowered" a/c unit, which has to be almost as good as having a smaller one...) - all our non-A/C cars received white paint jobs on the roof when I was a young'n... and I've been putting some serious thought into doing up my WJ that way.
When A/C was still restricted to higher-end vehicles, white roofs were extremely popular in some overseas markets, from Central and South America to Africa and Southeast Asia.



Even the DKW range, developed in Germany, had to get into the trend when it was made in Brazil. It's almost impossible to find a Brazilian DKW which didn't have a white roof...




Sometimes I wonder if this trend could come back...
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Old 06-18-2015, 12:13 PM   #27 (permalink)
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Smile The Definitive Study

0.5 mpg better fuel economy found with silver compact car with air conditioner in warm climate: Silver and white cars are cooler, says study
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Old 06-19-2015, 03:36 AM   #28 (permalink)
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Quote:
Overall, the numbers compiled in this car-color exercise found that using white or silver paint instead of black paint would raise fuel economy by 0.44 mpg (2.0 percent); would decrease carbon dioxide emissions by 1.9 percent, and reduce other automotive emissions by about 1 percent.
Wait, how is 0.44 MPG 2% of a Civic's fuel economy?

I am sitting at 45 MPG lifetime on my Civic, so if I painted my car silver, I would achieve 45.9 MPG?

Except... I do not use my air conditioner!

I do not drive with the windows open, either. I could smell better...
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Old 06-19-2015, 10:12 AM   #29 (permalink)
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Quote:
Originally Posted by Hyperaboutmpg View Post
0.5 mpg better fuel economy found with silver compact car with air conditioner in warm climate: Silver and white cars are cooler, says study
I am pretty sure that this has been discussed in another thread. But anyway, I decided not to do any painting in the end. The reason was the realization that once the car is moving the aerodynamic flow of air cools all the cars about equally. My car is black. Parked the roof gets wicked hot. Go for a drive and it cools down pretty fast. I doubt a while roof is a lot cooler when in motion. This means metalized or ceramic dark tint is your better cabin-cooling strategy, and I have already had that for four years (got lifetime warranty).
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Old 06-19-2015, 11:15 AM   #30 (permalink)
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Quote:
Originally Posted by Xist View Post
Wait, how is 0.44 MPG 2% of a Civic's fuel economy?

I am sitting at 45 MPG lifetime on my Civic, so if I painted my car silver, I would achieve 45.9 MPG?

Except... I do not use my air conditioner!

I do not drive with the windows open, either. I could smell better...
The assumption, of course, is that absolutely everyone behaves exactly as their simulations predict.

I love this idea and have considered going this route on the truck. It never had AC so anything to cool it off is good.

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