HTPB (Hydroxyl-Terminated Polybutadiene) (HO–(CH₂–CH=CH–CH₂)ₙ–OH) is a solid fuel binder propellant used as a fuel / binder. Excellent — stable for decades in solid motor form. Typical ISP: 240–270 s (in APCP composite, with aluminum) seconds.
HTPB is the most widely used binder and fuel in modern solid rocket propellants, providing the rubbery matrix that holds oxidizer particles and metal fuel in a castable composite. When combined with ammonium perchlorate and aluminum powder, HTPB forms the basis of APCP solid propellant. It offers excellent mechanical properties, good aging characteristics, and compatibility with most propellant ingredients.
Replaced earlier polybutadiene-acrylic acid (PBAA) binders in the 1970s. Now the standard binder for military and commercial solid rocket motors worldwide.
Excellent mechanical properties, castable, good aging, high solids loading, low cost
Cannot be shut down or throttled once ignited, lower Isp than liquid propellants
