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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. |
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#1
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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 |
#2
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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
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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
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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
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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
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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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