From: ahahma@polaris.utu.fi (Arno Hahma)
Newsgroups: sci.chem
Subject: Re: References on chlorine doners in pyrotechnics?
Message-ID: <1991Apr15.195758.19178@polaris.utu.fi>
Date: 15 Apr 91 19:57:58 GMT

In article <3200@oucsace.cs.OHIOU.EDU> bwhite@oucsace.cs.ohiou.edu (William E. White ) writes:

>chlorine doner, such as PVC or Parlon.  I asked a couple of local profs
>exactly what they are doing there, and nobody seems to be able to give
>a sure answer.  Could anyone suggest

>1) a reference or a short explanation as to the exact function of a
>chlorine doner in pyrotechnics

1) Chlorine makes the coloring ions more volatile. Oxides are hardly volatile
at all, they often have boiling points above 3000 K or more, whereas
chlorides have boiling points in the order of 1000..2000 K. As a result,
you get them better into the flame and get more light.

2) The coloring species is usually not an ion itself, but a molecule,
a radical or a multiple atom ion. As an example, Barium oxide emits
yellow light, barium monochloride ion emits green light (BaCl+).
This is the case with many ions, the chlorine is required
to make the color appear. The halogen can not be used as BaCl2, since
barium is used to carry the nececcary oxygen as a nitrate, usually. In
barium chlorate mixtures the chlorine is there already - this is why these
give better greens than nitrate based mixtures.

Blue stars are also dependent on a halogen. Copper hydroxide
CuOH+ (ionic) emits green, whereas CuCl+ emits blue. (I am not quite sure
if these were ionic or not.)

>2) a guideline as to when and what should be used (e.g., why do some
>mixes call for Parlon, others for PVC, etc.); a short list of the more
>common and popular chlorine doners would be greatly appreciated

Parlon contains about 70 % of chlorine, and PVC about 56 %. So, you can
get more chlorine to the mix with parlon - thus, it gives a slightly
better color. PVC is used, because it is readily available and costs
little. Also, these act as a binder and a chlorine donor, whereas
hexachloroethane and hexachorobenzene only donate chlorine; another binder
is required.

Inorganic chlorine donors are not that good, since, they tend to cool the
flame very much - the dissociation enthalpies of chlorides are large.
Ammonium perchlorate is often used as an oxidizer and a chlorine donor
simultaneously. Ammonium chloride can also be used, if the composition
is compatible with it and a cool flame is desired.

Some usual chlorine donors and their approximate chlorine contents:

Parlon   70 %
PVC      56 %
hexachloroethane  90 %
hexachlorobenzene 75 %
ammonium perchlorate 20 %
ammonium chloride  65 %

Any highly chlorinated plastic could be used as a donor/binder for stars.
I can't remember other practical donors off hand.

>3) some reference book that will give the properties of typical chlorine
>doner compound (e.g., thermoplastic/thermosetting, curing time if in
>resin form, physical characteristics, handling considerations and
>toxicity, etc.)

Highly chlorinated plastics are not curable resins, but polymers. They usually
dissolve into organic solvents, thus, the star powder can be readily mixed in.
Or alternatively, the polymer is used in a powdered form and some other
binder, like dextrin, is used. This method is also used with perchloro-
benzene and -ethane.

>4) where exactly to *get* them (PVC in non-resin form is an easy one; but
>what about Parlon, resin form PVC, etc.?)

I do not know any such resins. Acetone and chloroform will dissolve Parlon
very well up to a sirupy solution. Usually a 10 to 25 % solution is
used as a binder. PVC can be dissolved into tetrahydrofuran up to 20..25 %
. Powdered polymers (PVC mostly) can be used as such, mixed into
the star mass, and moistened with the solvent.

The star mass is then spread on a plate and cut into stars before it dries.
Another method is to add solvent while tumbling the powder in a bowl.
The powder becomes granulated and the granules grow, as they get wet of
solvent/solution and more mass sticks onto the surface. This method
requires some practice to produce nice, spherical stars of about an
uniform size.

Parlon is chlorinated rubber, used in some laquers and paints. HExachloro-
benzene and -ethane are more difficult, a chemical supplier might have them
as reagents at least. Colorless PVC hose is a good source for pure (almost)
PVC. This kind of a PVC contains plasticizers, but they do not matter at all.
There are only some per cent of them present. In fact, they only make the
mass more strong mechanically, it is not brittle, but somewhat elastic.

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