Introduction

Many different chemicals can be used in the production of a solid rocket motor. These chemicals can be combined to achieve a variety of different effects. Chemicals in known use are listed below

Chemicals

Binder

Binders form the mechanical linkage in the rocket fuel. Some binders are also used as fuels. These binders are known as "energetic binders" and are normally hazardous.

R-45 M - A type of Hydroxyl Terminated Polybutadiene (HTPB) . Contains a pre-mixed anti-oxidant for long term storage

R-45 HTLO -  A type of HTPB that contains no anti-oxidants. Lower viscosity than R-45M

Low Molecular Weight HTPB - Very low viscosity HTPB. Lower molecular weight. May improve castability and performance. May detrimentally affect density.

Polybutadiene Acrylonitrile (PBAN) - Common hobby binder. Requires Cure schedule. Also used in the Space Transportation System's Solid Rocket Boosters.

Curative

These chemicals begin the polymerization of the binder

Isocyanate MDI

Isophorone Diisocyanate (IPDI)

PAPI

Plasticizer

These chemicals reduce the viscosity of the uncured propellant. They make mixing and casting of propellants easier and facilitate higher solids loading.

Isodecyl Pelargonate 

Dioctyl Adipate (DOA)

Dioctyl Sebacate

Opacifiers

These chemicals increase the infrared energy transfer from the flame front into the propellant face and prevent premature ignition or detonation of propellant behind the burning face.

Powdered Graphite - Black Powder

Prussian Blue - Blue Powder. Produces a blue tinted propellant after curing.

Methylene Blue - Blue stain. Liquid. Helps lower solid loading.

Nigrosin - Best opacifier by mass.

TiO2 - Opacifier. Rejects radiative heating. Creates white propellant.

Fuels

Aluminum - More energetic than magnesium but requires a larger motor to properly take advantage of. Large incompletely burned particle can damage nozzle. Tendency to deposit slag inside motor.

Magnesium - Powdered. Burns completely, faster than aluminum. Useful in smaller motors.

Oxidizers

Substances which oxidize the fuel and binder to facilitate combustion.

Ammonium Perchlorate - Most common in amateur and professional composite propellants

Ammonium Nitrate - Extremely hygroscopic. Tends to produce a slower burning propellant than ammonium perchlorate.

Potassium Nitrate - Used commonly in "rocket candy" formulations. Lower performance than ammonium perchlorate or ammonium nitrate.

Stabilizers

Magnesium Oxide

Phenylnaphthalene

DTBHQ - 2,5-ditert-butylhydroquinone

Processing Aids

Lecithin

Silicon Oil - Reduces adherence to mixing bowl. Makes propellant pour better.

Polydimethylsiloxane (PDMS) - Surfactant, reduces sticking to the bowl and aeration during mixing. Allows for mixing at higher speeds. Improves particle wetting.

Binding Agents

Binding agents form a bond between the surface of Ammonium Perchlorate particles and the polymer matrix, embedding the particles strongly in the propellant web. This slightly slows burn rate and increases hardness.

HX-752 - Does not cause foaming. Requires refrigeration. Smells bad.

HX-878 (Tepanol) - May cause foaming due to ammonia generation during curing.

HX-868 - (Dynamar) Co-active with HX-752, increases functionality and decreases migration

Cross Linking Agents

Castor Oil - provides additional sites for the polymer chains to cross link with the curative and castor oil. Increases cured propellant hardness.

Chromatic Burn Additives

Copper Oxychloride - Blue (5%-10% by mass)

Strontium Carbonate - Red.

Flame Retardants

Melamine - Used when using HTPB as a liner material

Zinc Borate - improves char layer formation