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MMD > Archives > April 1998 > 1998.04.22 > 12Prev  Next


Black Shellac and Phenolic Spool Flanges
By Karl Petersen

The Ampico spool flanges I have which have been heated in the
attic have collapsed since the black shellac has softened at high
temperature.  This material is molded much like other compression
molded plastic by putting a blob of the correct weight into a mold,
heating the mold, cooling the mold, and removing the part.  Shellac
is resin from lac bugs and is a thermoplastic resin, which means it
softens with heat.

While it is true that Bakelite (Dr. Leo Baekeland) is compression
molded in much the same way, the Bakelite (catalyzed phenol formalde-
hyde and filler) material is a thermoset and does not change shape with
heat.  There is a chemical reaction during molding that is not
reversible.

The earliest Ampico B jumbo "program" rolls had black japanned aluminum
flanges.  Later flanges were compression molded in masticated cotton
phenolic which is now brown with a chewed cloth appearance.  The color,
as molded, was a deep amber.  The black shellac was wisely avoided
since, in such a large flange, it would not have been stable.   Nylon,
gutta-percha, acetate and nitrocellulose, available in the late 20s,
were all more expensive and/or less stable.

Ampico used masticated cotton filler in the big flanges, which was
somewhat extravagant.  Other fillers would have been wood pulp or
minerals such as calcium carbonate or talc.  Combinations of these
fillers are typically used in the black or dark brown Bakelite moldings
for telephone, radio, electrical and musical instrument use.

These materials may be tested to see if they are Bakelite, gutta-percha,
or a thermoplastic much as amber is tested to see if it is true
fossilized rosin, newer rosin or other gum product.  A hot wire is
pressed against an unobtrusive area to see if the material melts or
chars, and the odor emitted is evaluated against known samples.

Karl Petersen
Meridian, Idaho

 [ My 7 kg dictionary of 1927 says:
 [
 [ "masticator - One that masticates; a machine for cutting meat into
 [  fine pieces, one for masticating rubber, gutta-percha, or the like,
 [  or one for cutting leather into fine pieces."
 [
 [ It's the machine which makes hamburger from old beef !!
 [
 [ -- Robbie


(Message sent Wed 22 Apr 1998, 03:23:54 GMT, from time zone GMT+0700.)

Key Words in Subject:  Black, Flanges, Phenolic, Shellac, Spool

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