Binders, propellant

Propellants cast into rockets are commonly case-bonded to the motors to achieve maximum volumetric loading density. The interior of the motor is thoroughly cleaned, coated using an insulating material, and then lined with a composition to which the propellant binder adheres under the environmental stresses of the system. The insulation material is generally a mbber-type composition, filled with siUca, titanium dioxide, or potassium titanate. SiUca-filled nitrate mbber and vulcanizable ethylene—propylene mbber have been used. The liner generally consists of the same base polymer as is used in the propellant. It is usually appHed in a thin layer, and may be partially or fully cured before the propellant is poured into the rocket. 

B. D. Nahloosky and G. A. Zimmerman, Thermoplastic Elastomers for S olid Propellant Binders, AERPL-TR-86-069, Aerojet Tactical Systems Co., Sacramento, Calif., Dec. 1986. 

J. T. Gxsxe glmproved Specifications for Composite Propellant Binders for Army Weapon Systems,TR-T-19-16, A-aayMssAe Command, Huntsville, Ala.,July 1979. 

As an energetic polymer, poly(glycidyl azide) (PGA) mance solid propellant binder [63,64]. For this purpose,... 

Elastomeric Polybutadiene-acrylonitrile Solid propellant binder... 

Degradation of Polymeric Propellant Binders , Final Rept, under Contract N00017-74-C-4335 (1975) 39) W. Brenner B. Rugg, Feasi-... 

Chen, E.-T., Duo, Y.-Q., Luo, S.-G., Luo, Y.-J., and Tan, H.-M., Novel Segmented Thermoplastic Polyurethane Elastomers Based on Tetrahydrofuran/Ethylene Oxide Copolymers as High Energetic Propellant Binders, Propellants, Explosives, Pyrotechnics, Vol. 28, 2003, pp. 7. 

Various types of binders are used to formulate AP composite propellants. Binders such as HTPB and HTPE decompose endothermically or exothermically at the burning surface. The burning rates of AP composite propellants thus appear to be dependent on the thermochemical properties of the binders used. Figs. 7.17 and 7.18 show In r versus In p plots for AP composite propellants made with five differ-... 

Propellant Binder HTPB AP particle size (pm) 400 200 20 3 Catalyst BEFP... 

Uses. Solvent for cellulose ethers, esters, resins, and dyes liquid propellant binder in foundry cores manufacture of resins including furfuryl alcohol resin (furan resin) and furfuryl alcohol-formaldehyde resins... 

Probably in no other propellant binder system will one find the number of excellent examinations of propellant failure criteria as have been carried out on the urethane propellants. This can be partly attributed to dewetting of the oxidizer that occurs when many of these formulations are strained, the high ultimate elongations that have been obtained on many of them, and because of the large number of binder ingredient permutations that can be made. The development of propellant science owes much to the many investigations performed on these materials. 

A hydrocarbon prepolymer containing terminal carboxyl groups (28) is available to the propellant chemist. These polymers were synthesized to eliminate some of the variables found in the copolymers. The carboxyl groups can be made of the same types with like reactivity. These linear non-branched polymers impart greater extensibility to elastomeric formulations. The chemistry in propellants is similar to the random functionality polymer. As 20 years of the chemistry of crosslinked propellant binders is reviewed, one familiar with the art cannot fail to predict solid propellant formulations using these polymers tailored to the specific requirements of the solid rocket design with the confidence that any discipline of science can be practiced. 

In principle any diol/triol mixture which reacts with a diisocyanate will yield a network. However, to be useful as propellant binder, additional requirements must be met. The most important are low cure shrinkage, low reaction exotherm, rubbery characteristics down to arctic temperatures, good aging stability, and ease of handling during propellant manufacture. 

An average functionality of 2 does not necessarily mean that the binder prepolymer is of good quality. For example, an average functionality of 2 can be easily obtained by blending mono-, di-, and trifunctional binder constituents. However, such a practice would not be conducive to good mechanical properties of the cured propellant binder. 

Stress decay (relaxation) measurements of propellant binders are a way to obtain insight into the network structure of binder systems (29). In addition, high hysteretical losses appear to be associated with good tensile properties. Figure 5 shows a normalized stress-decay vs. time plot of a polyurethane elastomer. If the reference stress, [Pg.105]

Table VIII. Effect of the Absorption of Electrolyte Solution on the Low Temperature Modulus of a PPG Propellant Binder...

Thermodynamic Calculations (Specific Impulse). Prepolymers in propellant binders keep the concentration of urethane groups small. Their effect on ballistic properties is therefore negligible and need not be considered in thermodynamic calculations. The contributions of the binder to specific impulse, density, etc., are determined by the chemical backbone structure of the prepolymer. [A more comprehensive treatment of interior ballistics can be found in References 37, 42.]... 

A specific requirement of solid propellant binder polymers is the small tolerance allowed in the reproducibility of the product properties. As a result, some polymers that cannot be specified easily must be adjusted lot by lot in accordance with qualification tests. This is illustrated graphically by the data of Figure 1, where different lots of a carboxy-terminated polybutadiene procured to the same specification are compared with the different equivalents of the BITA (butylene imine adduct of trimesic... 

Binders A binder plays an important role in resisting conductive ignition by hot metal particles. Propellants whose binders decompose endothermically are considered excellent in this context. On the other hand, propellants with exothermically decomposing binders ignite as easily as nitrate ester propellants. Binders can be classified as inert and energetic binders. 

Reed, R., Jr. (1983) Propellant binders cure catalyst. US Patent 4,379,903. 

Development of an oxetane binder, poly(BAMO/AMMO) as an insensitive propellant binder. Proc. ADPA Inti. Symp. on Energetic Materials Technology, 1994, Orlando, Florida. 

Hamilton, R.S., Lund, G.K., and Hajik, R.M. (1995) Manufacture of polyether compounds having both imine and hydroxyl functionality for solid propellant binder. US Patent 5,414,123 Chem. Abstr., (1995) 123 (4), 87609 k. 

Colodny, P.C. (1984) Degradation studies of polybutadiene type propellant binders by chemorheological techniques. Proc. 15th Inti Ann. Conf. ICT, Karlsruhe, Germany, June 27-29,1984, pp. 

Lowrey, Silane Polysulfide Polymers as Solid Composite Propellant Binders , JApplPolymSci 11, 553-66 (1967) CA 67, 45694 (1967)... 

J.M. Hammond et al, Siloxane Polyurethane Composite Propellant Binders , AIAAJ... 

A.R. Young II R. Erlich, Trialkylaluminumtrialkylamine Adducts as Intermediates for High-Energy Propellant Binders and Thermally Stable Polymers , USP 3538135... 

Tiquid rubbers are polymeric products used primarily as adhesives, sealants, castable rubbers, and rocket propellant binders. The name liquid rubber comes from the properties of flowing at room temperature and curing to rubbery networks. These materials offer advantages over conventional elastomers in their ease of handling and processing as they can be readily pumped and mixed in low power (relative to normal rubber) equipment with resultant savings. 

A typical product has the following characteristics number average molecular weight, — 1800 carboxyl assay, — 1.1 meq./gram color, amber bulk viscosity (Brookfield synchrolectric viscometer) 70°F., 8000 poises, 100°F., 2000 poises, 150°F., 250 poises, and 250°F., 15 poises. The product can be cured with polyfunctional epoxides, aziridines, and isocyanates for applications such as thermoset and pressure sensitive adhesives, electronic component encapsulation, rocket propellant binders, epoxy flexibilizers, etc. Detailed vulcanization data can be obtained for the 1800 molecular weight material, EMD-590, from the Enjay Chemical Co., Cranford, N. J. 

Fig. 37.17. Curing reactions used in present propellants. Each reactant is di- or polyfunctional, so that high molecular weight polymers are formed as the propellant binder.

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