Why does white plastic turn yellow in Hawaii?

[SecondAttempt]

I am remodeling my house in Hawaii, mostly just installing tile but the scope has expanded to include new moulding, a bathroom renovation, painting, and now replacing the electrical outlets. All the 20 year old outlets are noticeably yellow compared to the wall plates and look terrible in the new upgraded space. Not expensive to replace and I can do it myself but does anyone know why this happens?

When I search online the usual explanation is sunlight. But this never happened in Arizona. I realize the tropical sun is more intense but where I live we have cloud cover at least half the time compared to less than 10% in Arizona. And most of these outlets are behind furniture and not only don't see direct sunlight but are usually in the dark.

And it's not just the outlets, the recessed lighting trim is the same way. This is not a rant because it's really a cheap fix after what I am spending on everything else. I'd just really like to understand the physics of what is going on here. My suspicion is that is has to do with humidity but that is pure speculation.

Does anyone know? Does this happen in Florida, Houston, and other humid areas?

 

[Andre1969]

It's not just UV rays that get to plastics, but heat, cold, humidity, and sometimes just old age.

Also, it's not constant exposure, but sometimes just an initial exposure that can start the chemical process going, and you don't see the results of it until years later.

I'm in Maryland, which is comparatively moderate (4 seasons, although lately winters have seemed mild, but rarely at the extremes of heat/cold/humidity/dryness/etc) and while I haven't paid much attention to electrical outlets, I've noticed other white (or often light gray/"bone" colored) plastics that would fade. I've had it happen with sneakers too, where the outsole would sometimes turn yellow with age. And that would be somewhat random...it could be a shoe I wore outside a lot as a "work" shoe, or a shoe that spent most of its life in a box in the closet. There's often no rhyme or reason to it, other than aging.

 

[Winemaker]

If the outlets are 20 years or older, they may have been Ivory and not White. That being said, most were made from Bakelite, which does discolor over the years.

 

[Aerides]

It's not just Hawaii, certainly happens in Florida. What was most noticeable was the white plastic can inside of my old ceiling flood lights. Those went within a few years. Almost would make you think someone was smoking before we replaced them.

As far as switches and plates we replaced those in 2007 and they look ok so far. But the downlights, ugh.

 

[Rocket Man]

It happens in our home in central Illinois. We have high humidity in the summers. We built our home 31 years ago. However, the yellowing has only occurred on some of our wall plates. Seems like the ones we had for cable TV outlets and bathroom outlets were the worst. Most of the standard plug plates and the light switch plates are okay. Because it only happens on some of the items, I have to think it has to do with the chemicals in certain plastics that may be different than in others.

 

[Luvdogs]

I'm in FL and yes, happens here on old smoke detectors, any white plastic. Even when I worked, the plastic on the copy machines would be yellow, remotes, etc.

But the good thing is if it is something that is removable, a shot of white spray paint will make it look like new.

 

[ncbill]

Heat kills them too.

Replaced many in an old mountain house which used baseboard heaters where the outlets were installed directly above.

The plastic was crumbling by the time I swapped them out 30+ years later.

 

[SecondAttempt]

Very interesting. The outlets were white not ivory. Interestingly the wall plates have retained their whiteness and as far as I know they are original. This also did not happen in Arizona where I used to live so I'm going to go with humidity being a major factor. Where I live the temperature extremes they see in the house are maybe 60-80 F so heat or cold would not be a factor.

The ceiling fan blades are also turning yellow so I'll be replacing those as well (the entire fan in some cases for decorative reasons and just the blades in others)

The main remodel was installing tile over a polished concrete floor in bad shape. But having an absolutely gorgeous new floor makes everything else look shabby! Fortunately most of the "everything else" is fairly cheap and I can do it myself.

 

[latexman]

Some are made from thermosetting resins, like Bakelite (I used to work in an old Bakelite plant in NJ), and they tend to yellow with many things, the biggest being UV exposure.

Some are made from nylon, and other plastics, and they tend to not yellow.

If it is a surface phenomenon, you may be able to treat it with hydrogen peroxide and oxidize/bleach the surface back, or closer, to it's original white. If it is a bulk phenomenon, you'll have to replace it.

 

[badatmath]

It happens in AZ sometimes. Not on outlet covers but my old smoke detectors were noticeably yellow. The one closest to a window much worse than the others.

 

[ProspectiveBum]

I’ve noticed the yellowing of white plastics in SoCal.

 

[SecondAttempt]

Class action suit? Just kidding. I'd make more money in Hawaii if I could sue for rust!

I appreciate all the responses. It's really a cheap fix since I can safely swap out outlets myself and they are dirt cheap. Just was wondering if anyone knew the cause.

Thanks for the replies

 

[Badger]

It happens all the time in Florida. My old white window unit air conditioner in the closed in porch slowly turned beige over the years. Outlet covers were replaced years ago so they are still OK. It is only plastic that is affected.

Cheers!