HTPB

Polymer-based rocket propellants are generally referred to as composite propellants, and often identified by the elastomer used, eg, urethane propellants or carboxy- (CTPB) or hydroxy- (HTPB) terrninated polybutadiene propellants. The cross-linked polymers act as a viscoelastic matrix to provide mechanical strength, and as a fuel to react with the oxidizers present. Ammonium perchlorate and ammonium nitrate are the most common oxidizers used nitramines such as HMX or RDX may be added to react with the fuels and increase the impulse produced. Many other substances may be added including metallic fuels, plasticizers, stabilizers, catalysts, ballistic modifiers, and bonding agents. Typical components are Hsted in Table 1. 

A large number of polymeric compounds have been investigated, but most modem propellants utilize prepolymers that ate hydroxy-functional polybutadienes (HTPB), carboxy-functional polybutadienes (CTPB), or a family of polyethylene oxides (PEGs) to form urethanes. Typical cure reactions... 

Parameter Poly-sulfi Poly-ur CTPB CTPB HTPB PBAN PBAA Buta-die... 

CTPB = carboxy-terminated polybutadiene HTPB = hydroxy-terminated polybutadiene PBAN = polybutadiene-acrylic acid-acrylonitrile and PBAA = polybutadiene-acrylic acid. 

L. P. Piper, HTPB PropellantMging CPTR 82-12, CPIA Pubhcations, Johns Hopkins University, Laurel, Md., June 1988. 

The higher heat of formation and less oxygen in the HTPB molecule implies a higher heat output with greater oxidizer loading capacity. However, more oxygen in the... 

PPG would allow more metal at the expense of the oxidizer to further energize the composition. In addition, HTPB is frequently preferred over PPG because of its superior mechanical properties, better aging characteristics, and lower glass-transition temperature (Tg). The latter is especially desirable because at low temperature, the higher strain rates produced by motor ignition decrease the elongation of the composite rather markedly. 

Figure 10 Curing curves for the HTPB and CTPB composite systems.

Refs 7,8,9, 10,12,13 15). Hence, information on HTPB is presented in some depth... 

The most significant use for HTPB propints is in ballistic missiles (Refs 12 13). The most unique usage is in the functioning of a laser by means of the chemical exhaust species-generated by a HTPB-Xmm Perchlorate fuel matrix (Ref 9)... 

Some ordn uses have been found for carboxyl terminated polybutadiene viz, as rocket motor liners for proplnt mixts contg HTPB (Ref 17) and as part of a terpolymer binder for propints (Ref 16)... 

Bonding Agents and Processing Aids for HTPB Propellants , Rept No S-205, Contract DAAH01-68-C-0632, Rohm Haas Co, Huntsville (1969) 6) A.M. Bedard, Evaluation of... 

Michigian, Selection and Evaluation of Bonding Agents for HTPB Propellants , Rept No ASPC-1085-26F, RKCR-75-18, Aerojet Solid Proplsn Co, Sacramento (1974) 15) G,... 

Thompson E.E. Day, Development of HTPB Propellant for Ballistic Missiles . Rept No AFRPLTR-74-68, Contract F04611-72-C-0048, Thiokol Corp, Brigham City (1974) 16) F.R. 

Liquid rubbers In order to improve the flexibihty of short glass fiber-reinforced epoxy composites, Kaynak et al. [53] modified the epoxy resin matrix with hydroxyl-terminated polybutadiene (HTPB) liquid mbber. A silane coupling agent was also used to improve the interfacial adhesion between glass fibers and epoxy matrix. However, Humpidge et al. [54] reported some unique processing problems for the resulting pasty mixmres when short textile fibers were incorporated in a hquid mbber medium. 

Fur HTPB gebundene Raketentreib- und Sprengstoffe haben sich DDI und IPDI, fur GAP Diole N100 als Harter bewahrt. 

Die heute gebrauchlichen hochpolymeren Binder sind Polysulfide ( PS ), Polybutadien-Acrylsaure ( PBAA ), Polybutadien-Acrylsaure-Acrylonitril ( PBAN ), Polyurethan ( PU ) und Polybutadien mit Carbo-xyl-Endgruppen ( CTPB ) und mit Hydroxylendgruppen ( HTPB ). 

Hydroxy-terminated polybutadiene (8) (HTPB) has been treated with dinitrogen pentoxide in methylene chloride. The product (9) is an energetic oligomer but is unlikely to find application because of the inherent instability of /3-nitronitrates." Initial peroxyacid epoxidation of some of the double bonds of HTPB followed by reaction with dinitrogen pentoxide yields a product containing vtc-dinitrate ester groups and this product (NHTPB) is of much more interest as an energetic binder (see Section 3.10)." ... 

Research efforts are ongoing into the use of dinitrogen pentoxide for the industrial synthesis of nitrated hydroxy-terminated polybutadiene (NHTPB) from epoxidated HTPB (Section 3.10). The reaction of aziridines with dinitrogen pentoxide is an important route to 1,2-nitramine-niU ates and these reactions are discussed in Section 5.8.1. ... 

The energetic nature of the azido group makes its incorporation into energetic polymers and binders very desirable. 3,3-Bis(azidomethyl)oxetane (BAMO) (28) and 3-azidomethyl-3-methyloxetane (AMMO) (33) are energetic monomers which on polymerization result in the energetic polymers poly[BAMO] (32) and Poly[AMMO] (34), respectively, both of which are under evaluation as potential energetic alternatives to HTPB in composite propellant formulations. ... 

Hydroxy-terminated polyester (HTPS) is made from diethylene glycol and adipic acid, and hydroxy-terminated polyether (HTPE) is made from propylene glycol. Hydroxy-terminated polyacetylene (HTPA) is synthesized from butynediol and paraformaldehyde and is characterized by acetylenic triple bonds. The terminal OH groups of these polymers are cured with isophorone diisocyanate. Table 4.3 shows the chemical properties of typical polymers and prepolymers used in composite propellants and explosives.E4 All of these polymers are inert, but, with the exception of HTPB, contain relatively high oxygen contents in their molecular structures. 

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