Polybutadiene acrylonitrile (PBAN) copolymer, also noted as polybutadiene

Polybutadiene

Polybutadiene is a synthetic rubber that is a polymer formed from the polymerization process of the monomer 1,3-butadiene.It has a high resistance to wear and is used especially in the manufacture of tires, which consumes about 70% of the production...

 — acrylic acid

Acrylic acid

Acrylic acid is an organic compound with the formula CH2=CHCO2H. It is the simplest unsaturated carboxylic acid, consisting of a vinyl group connected directly to a carboxylic acid terminus. This colorless liquid has a characteristic acrid or tart smell. It is miscible with water, alcohols,...

 — acrylonitrile

Acrylonitrile

Acrylonitrile is the chemical compound with the formula C3H3N. This pungent-smelling colorless liquid often appears yellow due to impurities. It is an important monomer for the manufacture of useful plastics. In terms of its molecular structure, it consists of a vinyl group linked to a nitrile...

 terpolymer.

This was the binder formulation widely used on the 1960-70's big boosters

Booster rocket

A booster rocket is either the first stage of a multi-stage launch vehicle, or else a strap-on rocket used to augment the core launch vehicle's takeoff thrust and payload capability. Boosters are generally necessary to launch spacecraft into Earth orbit or beyond...

 (e.g., Titan III

Titan III

The Titan IIIC was a space booster used by the United States Air Force. It was launched from Cape Canaveral Air Force Station, FL., and Vandenberg Air Force Base, CA. It was planned to be used as a launch vehicle in the cancelled Dyna-Soar and Manned Orbiting Laboratory programs...

 and Space Shuttle SRBs

Space Shuttle Solid Rocket Booster

The Space Shuttle Solid Rocket Boosters were the pair of large solid rockets used by the United States' NASA Space Shuttle during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or...

). It is also sometimes used by amateurs due to simplicity, very low cost, and lower toxicity than the more common hydroxyl-terminated polybutadiene

Hydroxyl-terminated polybutadiene

Hydroxyl-terminated polybutadiene 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). HTPB uses isocyanate

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...

s for curing, which have a relatively quick curing time; however, they are also generally toxic. PBAN based propellants also have a slightly higher performance than HTPB based propellants.

PBAN is normally cured with the addition of an epoxy

Epoxy

Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....

 resin, taking several days at elevated temperatures to cure.

PBAN will be used in future NASA missions, most notably the Constellation program, cancellation pending in Congress, as this copolymer was to be used in the first stage of the Ares I rocket in five segments.