Yes. Colored APCP was very important to me once long ago…... :-)
You want to use a pigment
<https://en.wikipedia.org/wiki/List_of_inorganic_pigments> , not a dye.
There are 2 problems attempting to color any polymer binder in presence of
metal, oxidizers, or reactive curatives:
1) Strong color fast pigments are based on inorganic metal oxides. Stable
metal oxides like those listed below impact burn rate even when used in very
small amounts.
2) Commercial dyes are organic compounds (mainly stabilized weak acids or
bases), which are easily reacted with metal, oxidizer, or curatives in APCP
and lose their color.
When It comes to pigments in APCP, there are not many color choices. Strong
primary colors in APCP are very hard to achieve. The powdered metals add
gray/silver tones, and HTPB/curative/modifiers cast amber tones. These off
color tones can be overcome, but it requires using large amounts (5-10%) of
total formulation as pigment, and this is not good for APCP. These high levels
reduce ISP, not to mention the various burn rate impacts.
Using any pigment requires careful formulation to ensure proper OVERALL
performance (not just burn rate). An overlooked problem with most naturally
occurring organic mineral oxides is the impurities found as they are mined from
ground. The common impurities are carbonates, sulfur, chloride/chlorate, and
other unwanted compounds. All of these impurity chemicals will impact APCP in
a negative way. Some are even hygroscopic, and as they pull moisture from air
– which can revert HTPB/isocyanate bonds creating liquid goo out of your APCP
grains during storage. So be sure to use >98% pure pigments, and/or expect to
fight different reactivity problems with each and every lot purchased.
A color list from a my fuzzy memory:
: These increase burn rate (chemical – grain color)
Red Iron Oxide - Red
Yellow Iron Oxide - Yellow
Carbon Black - Black
Chromium(III) oxide – Lime Green
Copper oxide - Black
Copper Oxychloride – Green (blue grey green with powdered metals)
Copper Carbonate
- Malachite – Green (common)
- Azurite – Blue (hard to find, requires higher than average chamber
temperature to achieve stable reaction as a catalyst)
: These reduce burn rate
Titanium Dioxide – Dirty White/Cream (Can increase burn rate in small levels,
but decreased burn rate above ~1%. Can also be used to enhance/brighten other
pigments.)
Zinc Oxide – White (also be used to enhance/brighten other pigments)
Barium Sulfate – White (plus green-yellow flame plume)
Zinc dust - Grey
Asphaltum – Brown
: Not recommended
- Ultramarine - Ranges from deep blue to light purple
Has highly random levels of sulfur, chlorides, carbonates; which interferes
with isocyanate curatives. Comes in many natural and synthetic forums, and
they all react differently.
- Cobalt Aluminate – Blue (Cobalt anything accelerates OH-NCO reaction
dramatically)
- Al/MG powder metals – Grey
Using only powdered Al/Mg to add color is dangerous. They emit & absorb
infrared energy in chamber and will cause spontaneous combustion inside the
rubber matrix and a catastrophic event. Always add something (carbon or
carbonate) to absorb infrared when using metal powders.
-Sulfur – Yellow (poisons OH-NCO reaction)
-Cadmium, Lead, Tin, Manganese anything
(Most inorganic pigments with these elements have organo-metal impurities that
accelerate OH-NCO reaction dramatically, 3-10 minute cure of next batch of
HTPB anyone?)
-Uranium oxide - Yellow (Radioactive!)
Have fun with color, and be very, very safe.
Cheers!
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On ;
Behalf Of Charlie Garcia
Sent: Wednesday, August 22, 2018 10:49 AM
To: (AR) ocket List
Subject: [AR] HTPB Dye
Hi All,
Does anyone here deliberately dye their grains, like AeroTech or CTI? In
particular I'm looking for a red dye, preferably in very small fraction or a
liquid. I've had the red dye that comes in RocketPoxy suggested to me. Thoughts?
Sincerely,
Charlie