Solid propellant plasticizers used

Solid propellants are used extensively in the aerospace industry to power ttussiles and rockets for military, commercial, and space apphcations. Propellant may comprise from 1 to 3 wt% of plasticizer such as dioctyl adipate." ... 

A form of cooling, and the one of prime interest, concerns ablative cooling. It is essentially a heat and mass transfer process in which mass is expended to achieve thermal dissipation, absorption, and blocking. The process is passive in nature, serves to control the surface temperature, and greatly restricts the flow of heat into the material substrate. As a result of these desirable attributes, ablative cooling (includes use of plastic compositions) has been widely used for thermal protection of solid propellant motors and less extensively in liquid propellant motors. 

Crosslinks can be controlled by the number of unsaturated sites in the polyester prepolymer. Theoretically if each molecule has only two reaction sites, then infinite, almost linear, chains could be obtained. Hence, average functionability and molecular weight distribution in the prepolymer are extremely important. Plasticizers can be used to advantage in adjusting the average properties of the binder as obtained in the solid propellant formulation. 

Dibutyl phthalate has multiple uses in a variety of materials. Primary uses for dibutyl phthalate are to soften and increase plastic flexibility, for example, in shower curtains, raincoats, food wraps, and car interiors to name a few. It has been used in insect repellents and as a solvent for perfume oil and resins. Dibutyl phthalate can be used as a plasticizer in nitrocellulose lacquers, elastomers, explosives, nail polish, and solid rocket propellants. Other uses include perfume fixative, textile lubricating agent, safety glass additive, printing inks, and adhesives. 

Plasticizer used in nitrocellulose lacquers, elastomers, explosives, nail polish and solid rocket propellants solvent for perfume oils perfume fixative textile lubricating agent safety glass insecticides printing inks resin solvent paper coatings adhesives insect repellent for textiles. 

Because of its higher density, HMX has replaced RDX in explosive applications for which energy and volume are important. It is used in castable TNT-based binary explosives, as the main ingredient in high-performance plastic-bonded explosives, and in high-performance solid propellants. 

Hazardous Decomp. Prods. Heated to decomp., burns and emits very toxic fumes of NOx NFPA Health 1, Flammability 1, Reactivity 0 Uses Stabilizer for nitrocellulose-based smokeless powd., in solid rocket propellants plasticizer... 

Plasticizers require excellent physical compatibility and greater safety at elevated temperatures during production, handling and use. ° Low temperatures also have an effect on these materials. If a plasticizer crystallizes solid propellant becomes brittle and has a tendency to crack, which causes irregrrlar brrming properties. Plasticizers often affect crrring rate of binder as seen in Figure 2.10. ... 

The LP polysulfides are used primarily as sealants and coatings for construction, transportation and chemical protection applications, and as a binder for solid rocket propellants. These uses will not be covered in this book, but there is a use for the LP series as reactive plasticizers for ST polysulfides to control viscosity but not seriously detract from final properties. 

Polystyrene. A thermoplastic used as a binder and fuel in expls and rocket propints. See Plastic fuels (Vol 3, C465-L) under Composite Propellants also Dinitropolystyrene in this Vol, N143-L to N144-R under Nitro Polymers and Propellants, Solid , also in this Vol... 

Uses. To implode fissionable material in nuclear devices to achieve critical mass as a component of plastic-bonded explosives and solid fuel rocket propellants and as burster charges in military munitions. 

Propellant Composition. In principle, any solid ingredient which is chemically compatible with nitrate esters can be introduced into the propellant by way of the casting powder. Any liquid ingredient used in the formulation must also be a plasticizer or co-plasticizer for nitrocellulose. In practice, three major families of compositions have been developed, differing in the composition of the casting powder (see Table I for typical compositions) ... 

The key to the successful application of high performance, pourable nitrocellulose plastisols lies in a reasonably priced, high quality source of fine-particle, at least partially colloided, spheroidal nitrocellulose. Here we are speaking of particles much finer than the well-known ball powder, produced by the Olin Mathieson Chemical Co. for small arms for over 30 years (7). Actually, particles on the order of 5-50/x diameter appear to be required to assure a reasonable continuum of uniformly plasticized nitrocellulose binder in a propellant containing 45% or more of combined crystalline oxidizer and powdered metal fuel. Such a continuum of binder is necessary to assure acceptable mechanical properties and reproducible burning characteristics of the finished propellant. Preincorporation of a certain content of the water-insoluble solids within the nitrocellulose microspheres is an effective means of helping to assure this continuum of binder and alleviates the requirements for extremely small ball size. The use of a total of 45% or more of crystalline oxidizer and (generally) metal fuel is essential if the propellant is to be competitive with other modern propellants now in service. 

The resin used to manufacture plastisol propellants must be dispersion grade. The resin particles should be spherical (18) (or nearly so), preferably a maximum diameter of about 30p or less (14, 17), free from porosity (14), and have a clean surface (15). This will permit the formation of a smooth, creamy plastisol when mixed with approximately an equal weight of the usual plasticizers for the polymer in question. Further, the plastisol of the resin and plasticizer must be capable of being heavily loaded with oxidizer and other fine solids to permit the formulation of a useful propellant composition. 

Compared at (Is)max, polyether and polybutadiene propellants have nearly identical densities since the higher density of the polyether binder, P = 1.0 (polybutadiene p 0.9), is offset by the lower solids content [p (NH4CIO4) = 1.95, p (Al) = 2.7]. At lower solids loadings the higher density of the polyether becomes a definite advantage. If nitro-plasticizers are used [p (nitroplasticizer) = 1.4] the 7S maN is shifted to appreciably lower solids loadings, so that the plasticizer is combined preferably with a polyether in order not to lose density. 

Effects of Curing Agent Type. Epoxide-Cured Propellant. Carboxyl-terminated polybutadiene is a linear, difunctional molecule that requires the use of a polyfunctional crosslinker to achieve a gel. The crosslinkers used in most epoxide-cured propellants are summarized in Table IV and consist of Epon X-801, ERLA-0510, or Epotuf. DER-332, a high-purity diepoxide that exhibits a minimum of side reactions in the presence of the ammonium perchlorate oxidizer, can be used to provide chain extension for further modification of the mechanical properties. A typical study to adjust and optimize the crosslinker level and compensate for side reactions and achieve the best balance of uniaxial tensile properties for a CTPB propellant is shown in Table V. These results are characteristic of epoxide-cured propellants at this solids level and show the effects of curing agent type and plasticizer level on the mechanical properties of propellants. 

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