SOLID ROCKET PROPELLANT WITH BLENDED TRIAZOLE PLASTICZER

A solid rocket propellant includes a blended plasticizer of at least two chemically different 3-nitro 1,2,4-triazoles.

BACKGROUND

Solid rocket motors typically include a cast solid propellant. Solid propellant may include oxidizer, fuel, or both, held together with a binder. Ignition of the solid propellant generates high pressure gas, which is expelled through a nozzle to generate thrust.

SUMMARY

A solid rocket propellant according to an example of the present disclosure includes a blended plasticizer of at least two chemically different 3-nitro 1,2,4-triazoles.

In a further embodiment of any of the foregoing embodiments, the blended plasticizer has a molar ratio from about 1.1:0.9 to about 0.9:1.1 of the two chemically different 3-nitro 1,2,4-triazoles.

In a further embodiment of any of the foregoing embodiments, the two chemically different 3-nitro 1,2,4-triazoles are independently selected from azidoethyl nitro-triazole, azidopropyl nitro-triazole, nitradoethyl nitro-triazole, and nitradopropyl nitro-triazole.

In a further embodiment of any of the foregoing embodiments, the two chemically different 3-nitro 1,2,4-triazoles are azidopropyl nitro-triazole and azidoethyl nitro-triazole.

In a further embodiment of any of the foregoing embodiments, the two chemically different 3-nitro 1,2,4-triazoles are 1-azidoethyl 3-nitro 1,2,4-triazole and 1-azidopropyl 3-nitro 1,2,4-triazole.

In a further embodiment of any of the foregoing embodiments, the blended plasticizer has a density from 1.51 grams per cubic centimeter to 1.63 grams per cubic centimeter.

In a further embodiment of any of the foregoing embodiments, the blended plasticizer has a glass transition temperature of −62° C. to −75° C.

In a further embodiment of any of the foregoing embodiments, the blended plasticizer has a thermal stability characterized by no weight loss up to 125° C. and 0.4% weight loss or less after 16 hours at 70° C.

A further embodiment of any of the foregoing embodiments includes a polymeric binder, wherein the polymeric binder and blended plasticizer have a total combined weight, and from 25% to 75% of the total combined weight is the blended plasticizer.

A solid rocket motor according to an example of the present disclosure includes a motor case, a nozzle attached with the motor case, and a solid rocket propellant disposed in the motor case. The solid rocket propellant has a blended plasticizer of at least two chemically different 3-nitro 1,2,4-triazoles.

In a further embodiment of any of the foregoing embodiments, the blended plasticizer has a molar ratio from about 1.1:0.9 to about 0.9:1.1 of the two chemically different 3-nitro 1,2,4-triazoles.

In a further embodiment of any of the foregoing embodiments, the two chemically different 3-nitro 1,2,4-triazoles are independently selected from the group consisting of azidoethyl nitro-triazole, azidopropyl nitro-triazole, nitradoethyl nitro-triazole, and nitradopropyl nitro-triazole.

In a further embodiment of any of the foregoing embodiments, the two chemically different 3-nitro 1,2,4-triazoles are azidopropyl nitro-triazole and azidoethyl nitro-triazole.

In a further embodiment of any of the foregoing embodiments, the two chemically different 3-nitro 1,2,4 triazoles are 1-azidoethyl 3-nitro 1,2,4-triazole and 1-azidopropyl 3-nitro 1,2,4-triazole.

In a further embodiment of any of the foregoing embodiments, the blended plasticizer has a density from 1.51 grams per cubic centimeter to 1.63 grams per cubic centimeter, a glass transition temperature of −62° C. to −75° C., and a thermal stability characterized by no weight loss up to 125° C. and 0.4% weight loss or less after 16 hours at 70° C.

A further embodiment of any of the foregoing embodiments includes a polymeric binder, wherein the polymeric binder and blended plasticizer have a total combined weight, and from 25% to 75% of the total combined weight is the blended plasticizer.

A solid rocket propellant according to an example of the present disclosure includes a blended triazole plasticizer with a density from 1.51 grams per cubic centimeter to 1.63 grams per cubic centimeter, and a glass transition temperature of −62° C. to −75° C.

In a further embodiment of any of the foregoing embodiments, the blended triazole plasticizer includes azidopropyl nitro-triazole and azidoethyl nitro-triazole in a molar ratio from about 1.1:0.9 to about 0.9:1.1.

DETAILED DESCRIPTION

FIG. 1schematically illustrates a cross-section of selected portions of an example solid rocket motor20, which is also an example of an energetic device. The solid rocket motor20generally includes a nozzle22and a solid propellant section24. The solid propellant section24includes a forward end24aand an aft end24b. The nozzle22is attached at the aft end24b. As will be appreciated, the solid rocket motor20may include additional components related to the operation thereof, which are generally known and thus not described herein.

The solid propellant section24includes a solid propellant26. Solid propellants may include at least a polymer-based binder and an oxidizer. Depending on the requirements of a particular design, a solid propellant may also include a solid fuel. In this example, the solid propellant26defines an elongated bore28. The geometry of the bore28may be cylindrical and may have radial fin slots or other features. Alternatively, the solid propellant26may not have a bore. The solid propellant26is disposed within a motor case30about a central axis A.

Upon ignition the solid propellant26reacts to produce high temperature and high pressure gas (combustion gas). The combustion gas flows down the bore28and discharges through the nozzle22to produce thrust.

Prior to use for producing thrust, the motor20may be in storage or may be transported. During storage or transport a motor may be subject to the ambient surrounding environmental conditions, stresses, shock, and the like. In particular, a solid propellant must be insensitive to detonation during transport and while in storage. In this regard, as will be discussed in further detail below, the solid propellant26includes a blended triazole plasticizer that has good energetic performance and enhanced insensitivity. As one example implementation, the blended triazole plasticizer is energetic and may be used instead of another energetic or non-energetic plasticizer, such as nitroglycerin or butane triol trinitrate

The solid propellant26includes a blended plasticizer of at least two chemically different 3-nitro 1,2,4-triazoles. As will be appreciated, the solid propellant may include additional constituents. For instance, the solid propellant26may include the blended plasticizer with a polymeric binder and an oxidizer. Depending on the design of the motor20, the solid propellant26may also include a solid fuel, such as one or more powders of aluminum, boron, or magnesium.

The amount of the blended plasticizer in the solid propellant26can be varied to vary insensitivity and energetic performance. For instance, the polymeric binder and blended plasticizer of the solid propellant26have a total combined weight, and from 25% to 75% of the total combined weight is the blended plasticizer. The relative amounts of each of the 3-nitro 1,2,4-triazoles can also be varied to vary density, thermal stability, and glass transition temperature. As an example, the blended plasticizer has a molar ratio from about 1.1:0.9 to about 0.9:1.1 of the two chemically different 3-nitro 1,2,4-triazoles. In a further example, the molar ratio is about 1:1.

The blended plasticizer may also be characterized by density and glass transition temperature. For example, the blended plasticizer has a density from 1.51 grams per cubic centimeter to 1.63 grams per cubic centimeter and a glass transition temperature of −62° C. to −75° C. In one further example, the density is approximately 1.52 grams per cubic centimeter and the glass transition temperature is approximately −62° C. The blended plasticizer may also have a thermal stability characterized by no weight loss up to 125° C. and 0.4% weight loss or less after 16 hours at 70° C. Further examples of blends and density are shown in Table 1 below.

The motor20may be fabricated by injecting or casting the solid propellant26in the case30. For instance, the constituents of the solid propellant26are mixed together and then injected or poured into the case or an appropriate mold. The mixture then cures, thus producing the final solid propellant26in the desired geometry. As an example, the solid propellant26may include the blended plasticizer, polymeric binder, an oxidizer, and optionally a solid fuel. Typically, these constituents will be mixed together with a curative. The curative may be added last to the mixture to prevent premature curing. The mixture is then poured into the case30or an appropriate mold to form the solid propellant26. The curative reacts with the binder to form crosslinks, which serve to make the binder elastic. Most typically, the blended plasticizer is physically mixed with the binder, but is not chemically bound to the binder.