[Jukebox-list] Re: Shrinking Plastic/ Discolouration

[Dicecco, Michael]

Great note Jim. 

I wanted to ask another question on the same subject. 

I have a 1938 Wurlitzer 500, that I bought in 1995. When I got it the
"white" plastic had turned all brown from the tobacco smoke of 60+
years. I used 409, and then water sanded the plastic to a nice almost
white colour. I put car wax on them, in hopes of preserving the brighter
results. However, an old timer jukebox guy predicted 10 years ago, that
the plastics would go brown again, and he was right! Within about 2-3
years they started getting brownish. Today, they look almost as dark as
when I originally got the machine.
The juke is not used that much, and is never exposed to direct sunlight.
What causes this continual discolouration? Is there any way of stopping
it? Or is it a natural oxidation of the plastic that cannot be stopped?

Thanks

Mike
-----Original Message-----
From: jukebox-list-bounces at lists.netlojix.com
[mailto:jukebox-list-bounces at lists.netlojix.com] On Behalf Of
dirksenj at bellsouth.net
Sent: 2007, November, 20 4:58 PM
To: Jukebox mailing list
Subject: Re: [Jukebox-list] Re: Shrinking Plastic

Plastics and molding techniques today are much better, but all plastic
shrinks. Plastic continues to shrink throughout it's lifetime, although
99% of shrinkage occurs within 20 minutes of de-molding. Because of
this, molds have to be built "bigger" than the actual plastic part size
so it will shrink down to the right size. This is partly to blame for
the poor-fitting repro plastics - I would imagine molds are made from
good originals, and the repros have shrunk down even more from there.
Most plastic will shrink 4 to
5 thou per inch (some less, some 4 times this), so depending on the type
plastic used and length of the part, you can have shrinkage of 1/8 inch
or more. Combine this with differences in cabinets (I would bet they
have swelled or warped over the years too) and you can see it would be
difficult to reproduce plastics that fit perfectly. Even though I'm
aware of this, I too have cursed installing these plastics.

Heat and UV light are the enemy (some chemicals too), so keep the juke
turned off when not in use and keep it away from the windows.

Jim "I'm no expert but do work in the plastic injection molding
business" 
Dirksen
----- Original Message -----
From: "Ron Rich" <ronnnrich at yahoo.com>
To: "Jukebox mailing list" <jukebox-list at lists.netlojix.com>
Sent: Tuesday, November 20, 2007 3:55 PM
Subject: Re: [Jukebox-list] Re: Shrinking Plastic


> Kyle,
>  Got news for you youngen--they do NOT "hold up"--Least the ones that
I 
> have replaced--
>  Ron Rich
>
> "Mechanical Music of S.F." <mechanicalmusic at hotmail.com> wrote:
>
> Ron.
> You old.
> The modern plastics should hold up much better. The formulas are much 
> different. The old stuff
> was literally vegetable proteins and polymers.
>
> Kyle ~
> Mechanical Music of San Francisco
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