Question about polycarbonate resin

[Black88GTA]

So, the headlights on my car get water in them. It's annoying and ugly, and I've been kicking around the idea of attempting to fix it.

The previous owner drilled holes in the lenses (i assume) to drain the water out so that the housings don't fill up. Just one of many hack job ghetto "fixes" this guy is responsible for that I've been undoing ever since I picked this car up. Unfortunately, these holes don't fix the condensation issue in the slightest. I want to fix this the right way, which involves baking them in the oven, opening them up, and resealing them. The problem now is these holes in the lenses that I need to fill.

So, my idea was to block off the back of the holes when the lenses are apart from the housings, melt down some polycarbonate, pour the melted resin in there to fill the hole, sand down smooth, buff, and then clearcoat. My question is, does melting PC with a lighter have any ill effects on the resin? Will it catch fire, or just melt? Or, would I be better off breaking it up into little pieces and then cooking it up in a spoon, crackhead style?

Also, what are some commonly found things around the house that would be a good source of resin material? I could use burned CD-Rs, but I'm looking for things that don't have foil / dye that I'd have to scrape off.

Input is welcomed. I'll post up some pics if / when I do it.

 

[RU482]

epoxy

 

[PottedMeat]

Where exactly are these holes? Are they at the bottom of the headlight as drainage - they aren't in the bottom front are they?

My dad's old car had the condensation/water fill problem in one headlight, but it was made of glass. I fixed the seal at the base of the bulb socket and used a shop vac on blow mode to dry out the compartment. Never had the problem again.

 

[drinkmorejava]

Depends what kind of polycarbonate; bisphenol A is thermoplastic. Melting pt is 267C. You'd want to heat it in some kind of container, any direct contact to the flame would probably burn or blacken it.

 

[Fenixgoon]

Originally posted by: drinkmorejava
Depends what kind of polycarbonate; bisphenol A is thermoplastic. Melting pt is 267C. You'd want to heat it in some kind of container, any direct contact to the flame would probably burn or blacken it.

yep, direct heat from a flame will definitely cause combustion/oxidation.

also, you may not need to get to the melting point completely, depending on exactly what you want to do. thermoplastics have a glass transition temperature above which they start behaving like a gooey rubber. glass transition temperature is roughly 150C.

edit: you should probably check out just buying polycarbonate sheets. the stuff can't be that expensive.

 

[Black88GTA]

Originally posted by: RU482
epoxy

Thought of this, but in my experience plastic epoxy doesn't bond that well. Plus, I don't know how it would hold up to constant weather, or if it would turn yellow, or cause a discolored / cloudy spot in the lens, etc... I'd prefer to use resin identical (or close) to that of the lens so that it bonds as seamlessly as possible with it.

Originally posted by: PottedMeat
Where exactly are these holes? Are they at the bottom of the headlight as drainage - they aren't in the bottom front are they?

Unfortunately, yes. Right in the front, on the bottom outside corners. :| These lights are 100% plastic, with existing vent tubes at the back which angle downward so as not to allow water in. So I'm not sure why these holes were put there in the first place - I guess this guy never thought to look for existing vents, or failure in the seal was letting in enough water where it was starting to fill up.

Originally posted by: Fenixgoon

Originally posted by: drinkmorejava
Depends what kind of polycarbonate; bisphenol A is thermoplastic. Melting pt is 267C. You'd want to heat it in some kind of container, any direct contact to the flame would probably burn or blacken it.

yep, direct heat from a flame will definitely cause combustion/oxidation.

also, you may not need to get to the melting point completely, depending on exactly what you want to do. thermoplastics have a glass transition temperature above which they start behaving like a gooey rubber. glass transition temperature is roughly 150C.

edit: you should probably check out just buying polycarbonate sheets. the stuff can't be that expensive.

This is sort of what I was thinking. I was worried that direct flame might char / blacken it. I know that I could technically heat it up to just above the glass transition temp to get it to flow enough to work with it. The thing is, I want this stuff to get hot enough so that when I pour it in the hole, it melts the resin around it enough for it to form a solid bond. I don't want to pour it in when it's too cold to bond properly with the resin around it, which may lead to either a poor seal around the repair, or even the plug falling out.

I do have a small sheet of scrap plexiglass here that I'm not using for anything. Would this work?

 

[blahblah99]

Originally posted by: Black88GTA
So, the headlights on my car get water in them. It's annoying and ugly, and I've been kicking around the idea of attempting to fix it.

The previous owner drilled holes in the lenses (i assume) to drain the water out so that the housings don't fill up. Just one of many hack job ghetto "fixes" this guy is responsible for that I've been undoing ever since I picked this car up. Unfortunately, these holes don't fix the condensation issue in the slightest. I want to fix this the right way, which involves baking them in the oven, opening them up, and resealing them. The problem now is these holes in the lenses that I need to fill.

So, my idea was to block off the back of the holes when the lenses are apart from the housings, melt down some polycarbonate, pour the melted resin in there to fill the hole, sand down smooth, buff, and then clearcoat. My question is, does melting PC with a lighter have any ill effects on the resin? Will it catch fire, or just melt? Or, would I be better off breaking it up into little pieces and then cooking it up in a spoon, crackhead style?

Also, what are some commonly found things around the house that would be a good source of resin material? I could use burned CD-Rs, but I'm looking for things that don't have foil / dye that I'd have to scrape off.

Input is welcomed. I'll post up some pics if / when I do it.

This is what I did when my headlights had moisture in them:

1) Bake them in an oven at around 150F for an hour or so to remove moisture. Careful not to go above 200F as polycarbonate starts to soften after that.
2) Heat up some tar and plug up the holes where the moisture entered.

 

[PottedMeat]

Can you get some Methylene Chloride? Cut a piece of polycarbonate to fit the hole or big enough to patch and bond it with the methylene chloride - http://74.125.95.132/search?q=cacheC0MnL8tvuQJ:www.nelsonresearchinc.com/Work-Mate...ate&cd=2&hl=en&ct=clnk&gl=us&client=firefox-a

edit: actually maybe take some polycarbonate bits and dissolve it to make a paste

 

[guyver01]

Isn't this post better off in the Garage?

 

[Black88GTA]

Originally posted by: blahblah99

Originally posted by: Black88GTA
So, the headlights on my car get water in them. It's annoying and ugly, and I've been kicking around the idea of attempting to fix it.

The previous owner drilled holes in the lenses (i assume) to drain the water out so that the housings don't fill up. Just one of many hack job ghetto "fixes" this guy is responsible for that I've been undoing ever since I picked this car up. Unfortunately, these holes don't fix the condensation issue in the slightest. I want to fix this the right way, which involves baking them in the oven, opening them up, and resealing them. The problem now is these holes in the lenses that I need to fill.

So, my idea was to block off the back of the holes when the lenses are apart from the housings, melt down some polycarbonate, pour the melted resin in there to fill the hole, sand down smooth, buff, and then clearcoat. My question is, does melting PC with a lighter have any ill effects on the resin? Will it catch fire, or just melt? Or, would I be better off breaking it up into little pieces and then cooking it up in a spoon, crackhead style?

Also, what are some commonly found things around the house that would be a good source of resin material? I could use burned CD-Rs, but I'm looking for things that don't have foil / dye that I'd have to scrape off.

Input is welcomed. I'll post up some pics if / when I do it.

This is what I did when my headlights had moisture in them:

1) Bake them in an oven at around 150F for an hour or so to remove moisture. Careful not to go above 200F as polycarbonate starts to soften after that.
2) Heat up some tar and plug up the holes where the moisture entered.

I was going to do this anyway to get the lens apart from the housing. I was planning on using silicone or 3M Windo-Weld to shore up the factory sealant holding the lens to the housing when I put them back together to fix any gaps in it.

The problem is, the holes that were drilled are right in the front, through the lens - I can't plug them with tar, it has to be clear resin or else the lights will look like shit.

Originally posted by: PottedMeat
Can you get some Methylene Chloride? Cut a piece of polycarbonate to fit the hole or big enough to patch and bond it with the methylene chloride - http://74.125.95.132/search?q=cacheC0MnL8tvuQJ:www.nelsonresearchinc.com/Work-Mate...ate&cd=2&hl=en&ct=clnk&gl=us&client=firefox-a

edit: actually maybe take some polycarbonate bits and dissolve it to make a paste

It's hard to accurately cut the material to fill the holes, as they are only about 1/8" in diameter. Making a paste may work, although I'd rather pour the resin in without anything added to it in order to make it look as seamless as I can. I was thinking about just drilling a bunch of holes in a sheet and then collecting the drill shavings and melting those down. I don't need a ton of material, just enough to fill 4 small holes, plus a bit extra to account for losses and any sanding / shaping needed for the repair to lay flush.

 

[RU482]

Originally posted by: Black88GTA

Originally posted by: RU482
epoxy

I just like epoxy. In fact, I think I will go look up the history of epoxy. Thanks subby, for your professional advice

 

[Black88GTA]

Originally posted by: guyver01
Isn't this post better off in the Garage?

Not necessarily. My question was about plastic resins / properties. The answers would be the same regardless of the object being repaired, automotive or not. This instance just happens to be related to headlight housings.

 

[ShockwaveVT]

Duct tape imo

 

[vjyper]

Originally posted by: ShockwaveVT
Duct tape imo

Clear packing tape. The stuff will stay on for years.