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Anyone know anything about plastics?


Tipex
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I've noticed recently that my headlights have a slight yellow tinge to them, and the clear wing mirror mounted indicator lenses more so, basically the plastic has been sand blasted after 140k of sitting on the car in fronts bumper (it's a taxi remember).

I've been researching on't internet, and seen many variations on basically the same method of restoring them, i.e. wet sanding with fine grit paper, then using plastic polish (they aren't badly yellowed so no need for heavier grit paper first), but one thing I've read in a couple of different places on admittedly American sites linked to bodyshops, is that once polished back to clear, the lenses wont have the factory 'protective coating' on them that prevents the yellowing, and that they can apply it for fee, or sell you the coating to apply yourself, but that it is very hard to apply as it wont adhere to the polished plastic surface.

Does anyone know if headlights do actually have any kind of coating on them? or is it just contained (if it exists) within the plastic itself before it's moulded into shape, and therefore still present if I sand and polish the lens myself?

I don't want to do it, and then for them to go yellow again in six months.

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They aren't badly yellowed, they just don't sparkle as much as they used to, I've seen plenty of youtube videos showing how it's done, and it seems to work pretty well, If I'm honest, I was going to do my own, then one of the mrs friends has a Yaris that the headlights are really bad on, was going to have a go at them, and then if successful start advertising it as a service, putting flyers on peoples cars in Tesco etc with bad headlights.

The sheer number of cars I see with badly yellowed/cloudy headlights makes me think there is money to be made here!

I was just wondering if I'd end up giving everyone their money back in six months if they didn't stay clear after reading about this 'coating' they have applied from the factory.

I did read somewhere on the internet that applying a coat of decent wax would also stop the yellowing from happening again.

Edited by Tipex
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They aren't badly yellowed, they just don't sparkle as much as they used to, I've seen plenty of youtube videos showing how it's done, and it seems to work pretty well, If I'm honest, I was going to do my own, then one of the mrs friends has a Yaris that the headlights are really bad on, was going to have a go at them, and then if successful start advertising it as a service, putting flyers on peoples cars in Tesco etc with bad headlights.

The sheer number of cars I see with badly yellowed/cloudy headlights makes me think there is money to be made here!

I was just wondering if I'd end up giving everyone their money back in six months if they didn't stay clear after reading about this 'coating' they have applied from the factory.

I did read somewhere on the internet that applying a coat of decent wax would also stop the yellowing from happening again.

That may be a distinct possibility....ok...30yrs since I did my Chemistry A-level...plastics are long chain polymers...prolonged exposure to UV light can knock off an electron...creating a free radical...very reactive...possibly causing oxidation and yellowing of clear plastics....exposed surface in contact with atmosphere will oxidize...polish off oxidized surface layer....exposing un-oxidized surface to atmosphere....whole process starts again....Not saying I`am right(Not a chemist)....but long chain polymers are susceptible to UV light(oxidation) and heat(melting) cold(brittle)...It may be worth looking up long chain polymer plastics on wiki....I know it can`t be relied on 100%....but most of the info seems pretty accurate these days

Well....UV light and Oxidation are issues...not sure if they affect the clear plastics used in headlights...etc..etc

Polymer degradation - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/UV_degradation

edit...I suppose a decent wax will act as a barrier between the surface of the plastic and the atmosphere.

Edited by Mr Man
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I worked for 10 Years in automotive lighting.

Our polycarbonate lenses had a laquered finish applied by robot and then cured in ovens.

The headlights on the S3 i have just changed had "gone" the laquer had tarnished and broken up with UV damage and possibly damage from machine polishing with the professional valets it had over its life. Equally it could have been blamed on wax burning onto the lense? I dont know. I certainly will not wax or allow a machine mop headlights again just in case.

Once the lacquer has gone, its never coming back you can only try and improve it.

I tried all sorts to improve it, to no avail. Maguires Plastic x did not touch it, nor did G3 and a machine buff.

The only product that had some effect, was a fluid i bought from the US. Pittman's ALR (google it) It was very expensive for a small vial and only lasted a short time in my case.

The next stage would have been wet sanding , which i didnt have the balls to try, and again, i would imagine would have a short lifecycle before it needed doing again.

Edited by Paul
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I worked for 10 Years in automotive lighting.

Our polycarbonate lenses had a laquered finish applied by robot and then cured in ovens.

The headlights on the S3 i have just changed had "gone" the laquer had tarnished and broken up with UV damage and possibly damage from machine polishing with the professional valets it had over its life. Equally it could have been blamed on wax burning onto the lense? I dont know. I certainly will not wax or allow a machine mop headlights again just in case.

Once the lacquer has gone, its never coming back you can only try and improve it.

I tried all sorts to improve it, to no avail. Maguires Plastic x did not touch it, nor did G3 and a machine buff.

The only product that had some effect, was a fluid i bought from the US. Pittman's ALR (google it) It was very expensive for a small vial and only lasted a short time in my case.

The next stage would have been wet sanding , which i didnt have the balls to try, and again, i would imagine would have a short lifecycle before it needed doing again.

Cheers, that's just the kind of info I was after, so they do have a coating on them, I guess a proper sand and polish wouldn't be much good then really unless just for a short period while selling the car then.

Well that's that money making scheme down the drain then!

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Indeed. It's amazing how much stronger the lenses were after lacquering. You could barely mark them.

Manufacturers included Vauxhall, Honda, Rover, Jaguar, Land Rover, Mercedes, Lamborgini all had the same process which we produced in the UK

Many other makes were done the same way throughout the world in our other plants.

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