Re: Secondary form coating.

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Scott Hanson" <huil888-at-surfside-dot-net> 

Harold -

As far as "alcohol" causing crazing of acrylic or polycarbonate, it's not
quite that simple.

Some alcohols will craze some acrylic, but the degree of attack, if any,
depends on several factors:

1. The type of alcohol. Most trouble is encountered with "denatured"
alcohol, which by US law can be denatured by the addition of a number of
different solvents, including gasoline, acetone, etc. The more aromatic
solvents like acetone will have the greatest tendency to cause crazing.

2. The amount of residual stress in the acrylic from fabricating or forming
operations. Material with a high level of residual stress may craze almost
instantly in the stressed areas, while the surrounding areas may remain free
from crazing.

3. The length of time the solvent is in contact with the plastic. The longer
the contact time (if solvent is allowed to wick into joints, etc) the
greater the tendency to craze.

In my experience, almost any type of alcohol is safe to use in a "wipe-down"
application, where a cloth slightly moistened with alcohol is used to
quickly wipe the surface of the part. The alcohol must completely evaporate
within a few seconds. Remember that common drug-store isopropyl alcohol has
a fair amount of water in it, and the alcohol will evaporate quickly but the
water takes a little longer.

Two types of acrylic tubing are commonly used as secondary forms coil-forms:
cast and extruded. Both types can be successfully cleaned with alcohol prior
to winding and coating if the alcohol-acrylic contact time is kept
reasonably short.

Regards,
Scott Hanson
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, February 08, 2004 7:47 AM
Subject: Re: Secondary form coating.


 > Original poster: "Harold Weiss" <hweiss-at-new.rr-dot-com>
 >
 > Hi All,
 >
 > Alcohol will craze plexiglass. (acyrlic)
 >
 > David E Weiss
 >
 >  > Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 >  >
 >  > Hi Ed,
 >  >
 >  > The solvents in the shellac are alcohols (methanol, ethanol, and
 >  > isopropanol).  i would think these would be OK.
 >  >
 >  > Gerry R
 >  >
 >  >  > Original poster: Ed Phillips <evp-at-pacbell-dot-net>
 >  >  >
 >  >  >>
 >  >  > I'd avoid any solvent-based lacquer with acrylic unless I'd done a
 >  >  > careful test first.  It can craze at times, but not like
polystyrene.
 > I
 >  >  > use shellac and it works fine for me, but there are probably better
 >  >  > materials.
 >  >  >
 >  >  > Ed
 >  >  >