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.
- 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.
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