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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

What causes white plastic cases to yellow?



 
 
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  #1  
Old June 24th 08, 09:07 PM posted to sci.electronics.repair
msg
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Posts: 412
Default What causes white plastic cases to yellow?

Greetings,

I would appreciate a discussion on what environmental factors
cause white plastic equipment cases (which thermoplastics are used
I don't know) to yellow to a sickening hue. I have a number of
devices that only in one room of the house have suffered this fate
over the last several years in storage. Some have been in boxes
and others in the open. The room is darkened with no solar
illumination and only occasionally are CFL lights used. One
device only yellowed on the surface facing the ceiling. There
is no smoking in the house and very little (only occasional)
fry-pan cooking at a low temperature.

What chemistry is involved here? Could carpet composition or
fire-retardant treating do this?

Michael
Ads
  #2  
Old June 24th 08, 11:21 PM posted to sci.electronics.repair
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Posts: 4,174
Default What causes white plastic cases to yellow?

msg wrote in message
ernet...
Greetings,

I would appreciate a discussion on what environmental factors
cause white plastic equipment cases (which thermoplastics are used
I don't know) to yellow to a sickening hue. I have a number of
devices that only in one room of the house have suffered this fate
over the last several years in storage. Some have been in boxes
and others in the open. The room is darkened with no solar
illumination and only occasionally are CFL lights used. One
device only yellowed on the surface facing the ceiling. There
is no smoking in the house and very little (only occasional)
fry-pan cooking at a low temperature.

What chemistry is involved here? Could carpet composition or
fire-retardant treating do this?

Michael


I've always assumed it was a surface oxidation process or from airbourne
acids. It can often be cut back with oven cleaner but any legends etc are
lost doing that. White paint goes yellow, paper goes brown in a reaction
with airbourne acids.

perhaps try sci.chem

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/





  #3  
Old June 25th 08, 09:28 PM posted to sci.electronics.repair
external usenet poster
 
Posts: 1,184
Default What causes white plastic cases to yellow?

On Jun 24, 12:07*pm, msg wrote:


I would appreciate a discussion on what environmental factors
cause *white plastic equipment cases... to yellow


There are two or three causes. Firstly, UV light can
cause 'color centers' to form, kind of like the purple tint
that develops in desert glass. Secondly, polymers
are developed from unstable (monomer) ingredients,
and there are complex aging characteristics, which
cause the plastics to shrink, embrittle, or change color.

Dirt, also, may bond to the surface; if normal household
cleaners (soap, Windex, Formula 409 etc.) don't work,
it might be useful to apply a mild abrasive (toothpaste
or metal polish).

Unusual cleaners including waterless hand cleaner,
denatured alcohol (for fingerprints on keyboards), dilute
lye (for smokestains), vinegar (for some mineral dusts)
have proven effective. Isopropyl alcohol is NOT
recommended for translucent or transparent plastics.
  #4  
Old June 26th 08, 02:10 AM posted to sci.electronics.repair
b
external usenet poster
 
Posts: 764
Default What causes white plastic cases to yellow?

On 24 jun, 12:07, msg wrote:
Greetings,

I would appreciate a discussion on what environmental factors
cause white plastic equipment cases (which thermoplastics are used
I don't know) to yellow to a sickening hue.


this was discussed recently elsewhere, lots on the subject:
http://www.vintage-radio.net/forum/s...ad.php?t=24333

HTH
  #5  
Old June 26th 08, 02:34 AM posted to sci.electronics.repair
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Posts: 3,792
Default What causes white plastic cases to yellow?

Dirt, also, may bond to the surface; if normal household
cleaners (soap, Windex, Formula 409 etc.) don't work,
it might be useful to apply a mild abrasive (toothpaste
or metal polish).

Novus, too.


  #6  
Old June 27th 08, 01:20 AM posted to sci.electronics.repair
external usenet poster
 
Posts: 22
Default What causes white plastic cases to yellow?

On Jun 24, 12:07*pm, msg wrote:
Greetings,

I would appreciate a discussion on what environmental factors
cause *white plastic equipment cases (which thermoplastics are used
I don't know) to yellow to a sickening hue. *I have a number of
devices that only in one room of the house have suffered this fate
over the last several years in storage. Some have been in boxes
and others in the open. The room is darkened with no solar
illumination and only occasionally are CFL lights used. *One
device only yellowed on the surface facing the ceiling. *There
is no smoking in the house and very little (only occasional)
fry-pan cooking at a low temperature.

What chemistry is involved here? Could carpet composition or
fire-retardant treating do this?

Michael


THE ONLY REASON WHY WHITE PLASTIC TURNS YELLOW IS BECAUSE MICHAEL
TERRELL FORGOT TO WIPE HIS CUM OFF IT AFTER GETTING HEAD FROM DON
BOWEY.
 




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