Hydroxyl-terminated polybutadiene
Encyclopedia
Hydroxyl-terminated polybutadiene (HTPB) is a polymer of butadiene terminated at each end with a hydroxyl
functional group
. It reacts with diisocyanate
to form polyurethane
, a stable and easily stored synthetic material.
HTPB is a translucent liquid with a very similar color to wax paper, it is highly viscous. The properties cannot be precisely stated, because HTPB is manufactured in various grades to meet specific requirements. HTPB is thus a generic name for a class of compounds. It consists of many butadiene molecules linked together into a polymer forming polybutadiene. Both ends of the chain are terminated with a hydroxide ion [OH-], thus giving it the name Hydroxyl-Terminated Polybutadiene. It is used in model rocketry as a high power fuel known commonly as RBS. It has also found its way into the pyrotechnics industry with a use as mortar tubes for aerial-shell fireworks. It is insoluble in water making it a good sealant. Although it is used in rocket fuel it does not ignite easily – it requires temperatures in excess of 773K to combust. The curing agent for it is usually a polyisocyanate compound.
motors to bind the fuel and oxidizing agent
into a solid mass. It is also used as a hybrid rocket
fuel. Together with N2O (nitrous oxide
, or "laughing gas") as the oxidizer, it is used to power the SpaceShipOne hybrid rocket motor developed by SpaceDev
. It also powers all 3/4 stages of the Japanese M-5 rocket
satellite launchers. JAXA describe the fuel as "HTPB/AP/Al=12/68/20" which means, proportioned by mass, HTPB 12% (binder and fuel), Ammonium perchlorate
68% (oxidizer), and Aluminium
powder, 20% (fuel).
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
functional group
Functional group
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part of...
. It reacts with diisocyanate
Isocyanate
Isocyanate is the functional group of elements –N=C=O , not to be confused with the cyanate functional group which is arranged as –O–C≡N or with isocyanide, R-N≡C. Any organic compound which contains an isocyanate group may also be referred to in brief as an isocyanate. An isocyanate may have more...
to form polyurethane
Polyurethane
A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are...
, a stable and easily stored synthetic material.
HTPB is a translucent liquid with a very similar color to wax paper, it is highly viscous. The properties cannot be precisely stated, because HTPB is manufactured in various grades to meet specific requirements. HTPB is thus a generic name for a class of compounds. It consists of many butadiene molecules linked together into a polymer forming polybutadiene. Both ends of the chain are terminated with a hydroxide ion [OH-], thus giving it the name Hydroxyl-Terminated Polybutadiene. It is used in model rocketry as a high power fuel known commonly as RBS. It has also found its way into the pyrotechnics industry with a use as mortar tubes for aerial-shell fireworks. It is insoluble in water making it a good sealant. Although it is used in rocket fuel it does not ignite easily – it requires temperatures in excess of 773K to combust. The curing agent for it is usually a polyisocyanate compound.
Uses
HTPB is used in many solid rocketSolid rocket
A solid rocket or a solid-fuel rocket is a rocket engine that uses solid propellants . The earliest rockets were solid-fuel rockets powered by gunpowder; they were used by the Chinese in warfare as early as the 13th century and later by the Mongols, Arabs, and Indians.All rockets used some form of...
motors to bind the fuel and oxidizing agent
Oxidizing agent
An oxidizing agent can be defined as a substance that removes electrons from another reactant in a redox chemical reaction...
into a solid mass. It is also used as a hybrid rocket
Hybrid rocket
A hybrid rocket is a rocket with a rocket motor which uses propellants in two different states of matter - one solid and the other either gas or liquid. The Hybrid rocket concept can be traced back at least 75 years....
fuel. Together with N2O (nitrous oxide
Nitrous oxide
Nitrous oxide, commonly known as laughing gas or sweet air, is a chemical compound with the formula . It is an oxide of nitrogen. At room temperature, it is a colorless non-flammable gas, with a slightly sweet odor and taste. It is used in surgery and dentistry for its anesthetic and analgesic...
, or "laughing gas") as the oxidizer, it is used to power the SpaceShipOne hybrid rocket motor developed by SpaceDev
SpaceDev
SpaceDev, a part of the "Space Systems Business" of Sierra Nevada Corporation, is prominent for its spaceflight and microsatellite work. It designed and built the hybrid rocket motors for Paul Allen's Tier One suborbital SpaceShipOne space program operated by Scaled Composites...
. It also powers all 3/4 stages of the Japanese M-5 rocket
M-5 rocket
The M-V rocket, also called M-5 or Mu-5, was a Japanese solid-fuel rocket designed to launch scientific satellites. It was a member of the Mu family of rockets. The Institute of Space and Astronautical Science began developing the M-V in 1990 at a cost of 15 billion yen...
satellite launchers. JAXA describe the fuel as "HTPB/AP/Al=12/68/20" which means, proportioned by mass, HTPB 12% (binder and fuel), Ammonium perchlorate
Ammonium perchlorate
Ammonium perchlorate is an inorganic compound with the formula NH4ClO4. It is the salt of perchloric acid and ammonia. It is a powerful oxidizer, which is why its main use is in solid propellants...
68% (oxidizer), and Aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
powder, 20% (fuel).
External links
- Technical Literature, from Sartomer, a manufacturer of HTPB
- US Patent 5159123 description of synthesis and other details.