Yellowed interior shell

[boybach]

Anything recommended to re-whiten or de-yellerfy the surface? I can get it done in a slow slow fashion with acetone but anything better out there?

Larry
--
Larry - Victoria BC -

1977 Palm Beach VIN TZE167V101295 - 39,000 miles, PO said everything working but forgot the word NOT. New wiper blades, New SS exhaust system ..

 

[sgltrac]

Clean and paint it.

Sully
Bellevue wa

> Anything recommended to re-whiten or de-yellerfy the surface? I can get it
> done in a slow slow fashion with acetone but anything better out there?
>
> Larry
> --
> Larry - Victoria BC -
>
> 1977 Palm Beach VIN TZE167V101295 - 39,000 miles, PO said everything
> working but forgot the word NOT. New wiper blades, New SS exhaust system ..
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[mark sawyer]

Well.... Not sure what kind of plastic the GMC shells are... But if it is ABS, the Starwars reenactors may have you covered:

https://www.instructables.com/Restoring-yellowed-Stormtrooper-armor/

Story I read was there were some Starwars cosplay people that also happened to be chemical engineers specializing in plastics. They got together on
some Starwars internet forum and actually did some chemical analysis on the yellowed storm trooper helmets(took the helmets into work and ran them
through some sort of chemical analyzer)

Anyway, they supposedly came up with this method of using an oxidizer and sunlight to undo the yellowing.

Here are the Cliffs Notes:

The yellowing of ABS when exposed to Ultraviolet light is the result of a flame retardant added to the plastic during the manufacturing process. The
most common of which is tetrabromobisphenol –A, or TBBP-A. When exposed to UV light the TBBP-A degrades allowing Bromine to become a free radical.
The bromine forms a bond with readily available oxygen and causes the yellow color.

By irradiating the ABS with UV light in the presence of more hydrogen atoms, in the form of hydrogen peroxide, we break the bonds between the oxygen
and bromine and allow the bromine to bond with the hydrogen, thus reversing the discoloration.

To me, that right there is the internet at it's finest....

--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX

 

[Rob]

The Vintage Apple Macintosh folks also restore their old cases using a
similar method:

https://www.youtube.com/watch?v=_ewI7nMgrB8

Rob
Victoria, BC
76 Royale - Rear Twins/Dry Bath

> Well.... Not sure what kind of plastic the GMC shells are... But if it is ABS, the Starwars reenactors may have you covered:
>
> https://www.instructables.com/Restoring-yellowed-Stormtrooper-armor/
>
> Story I read was there were some Starwars cosplay people that also happened to be chemical engineers specializing in plastics. They got together on
> some Starwars internet forum and actually did some chemical analysis on the yellowed storm trooper helmets(took the helmets into work and ran them
> through some sort of chemical analyzer)
>
> Anyway, they supposedly came up with this method of using an oxidizer and sunlight to undo the yellowing.
>
> Here are the Cliffs Notes:
>
> The yellowing of ABS when exposed to Ultraviolet light is the result of a flame retardant added to the plastic during the manufacturing process. The
> most common of which is tetrabromobisphenol –A, or TBBP-A. When exposed to UV light the TBBP-A degrades allowing Bromine to become a free radical.
> The bromine forms a bond with readily available oxygen and causes the yellow color.
>
> By irradiating the ABS with UV light in the presence of more hydrogen atoms, in the form of hydrogen peroxide, we break the bonds between the oxygen
> and bromine and allow the bromine to bond with the hydrogen, thus reversing the discoloration.
>
>
>
> To me, that right there is the internet at it's finest....
>
>

 

[boybach]

Well all good suggestions, thanks!

I wonder how long the UV light has to stay on ...minutes? hours? days?

Larry
--
Larry - Victoria BC -

1977 Palm Beach VIN TZE167V101295 - 39,000 miles, PO said everything working but forgot the word NOT. New wiper blades, New SS exhaust system ..

 

[Ken B]

> Clean and paint it.
>
> Sully
> Bellevue wa

X2.

I did mime about 15 years ago with rattle can paint for plastic from Menards and it still looks great.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

 

[Ken H.]

X3

About 20 years ago there was one paint renowned for use on plastic. I
don't recall the name and can't find it online now, but there are a LOT of
brands explicitly for plastics now. Mine all look, AFAIK, just like they
did an hour after I re-installed them. I think unpainted they'd be
yellowed again.

Ken H.

> > Clean and paint it.
> >
> > Sully
> > Bellevue wa
>
> X2.
>
> I did mime about 15 years ago with rattle can paint for plastic from
> Menards and it still looks great.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[powwerjon]

Over the last 20 years on the coach interiors that I have done I used Krylov Fusion paint for plastic with excellent results. Comes in many colors and easy to apply. Just a good cleaning of the plastic and a light rub with 204 paper. Did my rear cap and any other misc pieces in our 77 during the interior restoration. Available at big box stores and Ace Hardware.

J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan

>
> X3
>
> About 20 years ago there was one paint renowned for use on plastic. I
> don't recall the name and can't find it online now, but there are a LOT of
> brands explicitly for plastics now. Mine all look, AFAIK, just like they
> did an hour after I re-installed them. I think unpainted they'd be
> yellowed again.
>
> Ken H.
>
>

>

>>> Clean and paint it.
>>>
>>> Sully
>>> Bellevue wa
>>
>> X2.
>>
>> I did mime about 15 years ago with rattle can paint for plastic from
>> Menards and it still looks great.
>> --
>> Ken Burton - N9KB
>> 76 Palm Beach
>> Hebron, Indiana
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:

 

[mark sawyer]

I've used SEM plastic paint in the past with good results...

I believe they make an adhesion promoter as well that you can wipe or spray on the plastic before applying paint that will kind soften up the plastic
which apparently helps the paint stick...

I would consider this a mandatory step, unless you want to do the whole panel again when it starts to flake off in a few months...

Also, before using the adhesion promoter, you need to clean the heck out of the plastic... Any silicone (from armor all or whatever), grease, oil
etc. and the paint will flake. I believe SEM makes a product for this too.

Painting plastic can be hit or miss... But I've found if you follow the whole system for whatever brand you choose, (Cleaner, Prep, Adhesion
Promoter, etc.) you have the best chance of the paint not flaking down the road....

--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX

 

[sgltrac]

Sanding should not be necessary unless you need to correct surface flaws.
Scrub the plastics with a strong water based cleaner and red scotchbrite
pads, rinse well with water, dry and spray.

Sully
Bellevue wa

> I've used SEM plastic paint in the past with good results...
>
> I believe they make an adhesion promoter as well that you can wipe or
> spray on the plastic before applying paint that will kind soften up the
> plastic
> which apparently helps the paint stick...
>
> I would consider this a mandatory step, unless you want to do the whole
> panel again when it starts to flake off in a few months...
>
> Also, before using the adhesion promoter, you need to clean the heck out
> of the plastic... Any silicone (from armor all or whatever), grease, oil
> etc. and the paint will flake. I believe SEM makes a product for this too.
>
> Painting plastic can be hit or miss... But I've found if you follow the
> whole system for whatever brand you choose, (Cleaner, Prep, Adhesion
> Promoter, etc.) you have the best chance of the paint not flaking down the
> road....
>
>
> --
> Mark S. '73 Painted Desert,
> Manny 1 Ton Front End,
> Howell Injection,
> Leigh Harrison 4bag and Rear Brakes,
> Fort Worth, TX
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[Jim Hupy]

What Sully said!!. It is really no big deal. Most important step is to
clean all the cigarette smoke, cooking grease, etc from the surface. One
thing to keep in mind. Most, if not all, sheet moulded plastics are LOADED
with release agents to make them easy to get out of the molds. Aggressive
sanding will expose more of them to the surface. PAINT WILL NOT ADHERE TO
MOLD RELEASE AGENTS. SO, easy on the sanding here. All I got!
Jim Hupy
Salem, Oregon

> Sanding should not be necessary unless you need to correct surface flaws.
> Scrub the plastics with a strong water based cleaner and red scotchbrite
> pads, rinse well with water, dry and spray.
>
> Sully
> Bellevue wa
>
> On Thu, May 6, 2021 at 7:14 AM Mark Sawyer

>
> > I've used SEM plastic paint in the past with good results...
> >
> > I believe they make an adhesion promoter as well that you can wipe or
> > spray on the plastic before applying paint that will kind soften up the
> > plastic
> > which apparently helps the paint stick...
> >
> > I would consider this a mandatory step, unless you want to do the whole
> > panel again when it starts to flake off in a few months...
> >
> > Also, before using the adhesion promoter, you need to clean the heck out
> > of the plastic... Any silicone (from armor all or whatever), grease, oil
> > etc. and the paint will flake. I believe SEM makes a product for this
> too.
> >
> > Painting plastic can be hit or miss... But I've found if you follow the
> > whole system for whatever brand you choose, (Cleaner, Prep, Adhesion
> > Promoter, etc.) you have the best chance of the paint not flaking down
> the
> > road....
> >
> >
> > --
> > Mark S. '73 Painted Desert,
> > Manny 1 Ton Front End,
> > Howell Injection,
> > Leigh Harrison 4bag and Rear Brakes,
> > Fort Worth, TX
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> >
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
>

 

[Richard RV]

Most paint manufacturers now have paint formulations with primer and paint in one, both for house paint and spray paint, which makes painting,
touch-ups and clean-up a lot easier.

I've used Rustoleum Universal Paint and Primer in One both inside and outside the coach. Inside I just clean and degrease the plastic and spray away.
On the outside I wiped down the roof with acetone and sprayed. It's tough stuff. You can scrub away on it and use regular household cleaners with
no worries. It's also a lot cheaper and more readily available than automotive brand specialty paints like SEM.

Richard

--
'77 Birchaven TZE...777;
'76 Palm Beach with 18,477 verified miles;
‘76 Edgemonte

 

[slc]

Back in the days when monitors were made of that white plastic, with aging the white plastic would turn to yellow
and look really really old.
They found that wiping the plastic down with hydrogen peroxide helped restore the white color again.

I never did this so I don't know how abrasive or otherwise the hydrogen peroxide is to the plastic
so try in on a spot that is not obviously visible.

let us know how it works out.
--
GatsbysCruise. \
74GMC260 Former Glacier Model style. \
Waukegan, Illinois \ Keep those MiniDiscs Spinning \ MY GREYHOUND IS FASTER THAN YOUR HONOR ROLL STUDENT \ WindowsXP-Win7-Win8.1-UBUNTU STUDIO -
UBUNTU VOYAGER - Berzin Auto Center

 

[MikeB]

I restored a 1949 stove that had plastic end caps on chrome handles. The end caps were disgustingly yellow from 70 years of grease and smoke. I
dropped them in a cup of hot water and oxyclean detergent. Cleaned and whitened like new after 6 hours. Did not effect texture of the plastic. Not
sure how you’d do a large ceiling cap. Also not sure how long it would take to return to yellow. It’s been a year of use with no yellowing.
--
M Beam
75’ Avion
TBI EBL , 3.70 LSD and other stuff
Zuki Sidekick,
Dozier Al