HTPB is a translucent liquid with a color similar to wax paper and a viscosity similar to corn syrup. The properties cannot be precisely stated because HTPB is a mixture rather than a pure compound, and it is manufactured to meet customers' specific requirements. An oligomeric unit typically consists of 5–10 butadiene molecules linked together, with each end of the chain terminated with a hydroxyl [OH] group:
Polyurethanes prepared from HTPB can be engineered for specific physical properties; polyurethanes may be highly elastic or tough and rigid. Some products include: rigid foam insulation panels; durable elastomeric wheels and tires (such as roller coaster and escalator wheels); automotive suspension bushings; electrical potting compounds; high-performance adhesives; surface coatings and surface sealants; synthetic fibers (e.g., Spandex); carpet underlay; hard-plastic parts (e.g., for electronic instruments); hoses and skateboard wheels.
An important application of HTPB is in solid rocket propellant. It binds the oxidizing agent and other ingredients into a solid but elastic mass. The cured polyurethane acts as a fuel in such mixtures. For example, HTPB is used in all 3/4 stages of the Japanese M-5 rocket satellite launchers and PSLV rocket developed by ISRO for satellite launches. JAXA describe the fuel as "HTPB/AP/Al=12/68/20", which means, proportioned by mass, HTPB plus curative 12% (binder and fuel), ammonium perchlorate 68% (oxidizer), and aluminium powder 20% (fuel).
Similar propellants, often referred to as APCP (ammonium perchlorate composite propellant) are used in larger model rockets. A typical APCP produces 2–3 times the specific impulse of the black powder propellant used in most smaller rocket motors.
HTPB is also used as a hybrid rocket fuel. With N2O (nitrous oxide, or "laughing gas") as the oxidizer, it is used to power the SpaceShipTwo hybrid rocket motor developed by SpaceDev. It will also be oxidized by high-test peroxide in the land speed record attempt Bloodhound SSC.
- G. P. Sutton and Oscar Biblar, Rocket Propulsion Elements, (Eighth edition), pp. 595–599, John Wiley and Sons 2010.
- "SpaceDev Hybrid Propulsion". SpaceDev.
- poly-bd-liquid-polybutadiene hydroxyl-terminated, from Cray Valley, a manufacturer of HTPB
- US Patent 5159123 description of synthesis and other details.
|This article about polymer science is a stub. You can help Wikipedia by expanding it.|