Explosive and thermic compositions or charges – Structure or arrangement of component or product – Solid particles dispersed in solid solution or matrix
Reexamination Certificate
1986-02-18
2001-03-06
Miller, Edward A. (Department: 2204)
Explosive and thermic compositions or charges
Structure or arrangement of component or product
Solid particles dispersed in solid solution or matrix
C149S019100, C149S019400, C149S019910, C149S019900
Reexamination Certificate
active
06197135
ABSTRACT:
BACKGROUND OF THE INVENTION
Energetic composites are conventionally composed of a solid oxidizer dispersed within and bonded by a fuel matrix. The fuel matrix may optionally contain additional components such as powdered metals which act as high energy fuel and minor amounts of special purpose additives, plasticizers, antioxidants, wetting agents, curatives, and reinforcing and bonding agents.
For optimum results, each non-soluble composite component should be uniformly dispersed to a discrete small particle size in order to assure maximum energy conversion. Typically, it is advantageous to maximize the level of oxidizer and high energy fuel components while minimizing the level of binder component since most binder materials are poorer specific energy generators. Typically, additives such as plasticizers, antioxidants and wetting agents are introduced primarily to enhance the processability or the stability of the binder component of the system. Therefore, a reduction in the level of binder further reduces the need for these low energy components with consequent significant improvement in performance of the composite. Since, generally, the minimum amount of binder is determined by processability, this factor is one of the primary limitations on the performance of an energetic composite.
Various related formulations using metallo-organic compounds, especially aluminum III alkoxylates, monoalkyl silicon IV tris alkoxylates and monoalkoxy titanium IV tris salts of various types, when employed in modest proportions, have been shown to improve processability of a variety of composites. The titanate salts, particularly, are effective in enhancing dispersion of inorganic particulate in organic matrix binders such as those conventionally employed as matrices for energetic compositions.
BRIEF DESCRIPTION OF THE INVENTION
It has now been surprisingly found that neoalkoxy titanium IV and zirconium IV tris salts, most particularly those of the bis ester phosphate and pyrophosphate type, are not only effective processability enhancers but that, when used in proportions of the order from 0.01 to 5%, and more preferably from 0.1 to 2% of the total formulation (exclusive of volatile solvents and/or inert carrier materials), they will provide enhanced composite physical properties, reduced burn rates and greater product uniformity (resulting in enhanced handling safety) and less pressure sensitivity as compared to the prior art. In the energetic formulations tested, the addition of the additives of the instant invention provided positive rheological benefits, specifically a tendency toward Newtonian flow behavior, and an increase in critical particulate solids volume capabilities, thereby increasing inherent specific energy possible at constant formulation viscosity. The organo-titanate additives, surprisingly, reduce burn rate significantly, whereas the corresponding organo-zirconium derivatives have the reverse effect as compared to control experiments.
Solid propellants are conventionally composed of finely divided inorganic oxidizer material; organic resin which may serve as both a fuel and a binder; additional powdered metals which provide additional combustible material; and minor amounts of other additives such as plasticizers, antioxidants, wetting agents, curatives, metal oxides, and reinforcing agents.
Generally speaking, oxidizers are powdered and vary in size broadly from 1 to 300 microns average particle size, preferably in the range of from 20 to 200 microns. These materials form the major portion of the total composition, generally ranging from 65 to 95% of the total mixture. The fuel binder is usually present in minor proportions of the total composition, generally ranging from 5 to 35% by weight. Generally, it is advantageous to reduce the amount of binder material which is present, since such material adds weight to the total charge and its energy generation per unit weight is less than that provided by powdered metal fuels. The foregoing compositional factors are conventional to the art and described in detail in U.S. Pat. No. 3,050,423.
DETAILED DESCRIPTION OF THE INVENTION
It is preferred to admix in situ the organo-metallics of the instant invention with a fluid component of the matrix in advance of introduction of particulate for best results. It is also possible to pretreat particulate solids with the additives before introduction into the matrix material. However, additive pretreatment increases processing cost and handling hazards as compared to the in situ techniques. The methods of mixing of the energetic components and additives is known to those skilled in the art. Extruders or batch units such as the common sigma blade, ribbon blender, vertical two blade planetary, or other medium shear mixers, all preferably jacketed and equipped with heating and cooling capabilities external to the mixing bowl, may be used. Such equipment minimizes the potential for thermal runaway and permits the adjustment and control of process temperatures during the mixing operation. The objective of the mixing procedure is to fully wet and deagglomerate the oxidizer and optional energetic fuel particulate in the fluid binder at processing temperatures in order to maximize product uniformity and dispersion. Generally, after mixing, the resultant formulation is formed into the desired shape prior to use as an energetic composite. The forming can be achieved via a variety of well-known technologies including, but not limited to, casting, impregnation, extrusion, and tableting. The objective is to provide a viable, relatively easy to handle product which can be used as a source of energy for rocketry, ballistic propulsion, explosives, fuse materials, chemical welding and the like.
Current propellant binder systems include, but are not limited to, polybutadiene acrylic acid (PBAA), polybutadiene acrylic acid acrylonitrile (PBAN), carboxyl terminated polybutadiene (CTPB), hydroxyl terminated polybutadiene (HTPB), polysulfides, polyether urethanes, polyester urethanes, unsaturated polyesters and acrylics, epoxies, and nonreactive binders such as polyvinyl chloride (PVC), and nitrocellulose (NC) plastisols.
In all cases, the polymeric compound “binds” all propellant ingredients to form an aggregate or composite of sufficient strength to withstand the thermal and mechanical loads of motor operation and vehicle flight.
The neoalkoxy compounds of this invention may be used to advantage in most propellant binders. Positive effects are observed in the carboxyl terminated butadienes with a total absence of the cure rate problems normally associated with CTPB binders.
Where polyurethane systems are employed, it is useful to prepare a two-part system consisting of a premixed polyol part which contains the majority of the ingredients and a curative part which is composed primarily of the isocyanate curative. Such techniques will be readily understood by those skilled in the art.
Other elastomers which may be used as the binder are hydroxyl terminated butadiene prepolymers such as R45HT made by Arco Chemical Co. and having a functionality of about 2.7. These are described in U.S. Pat. No. 3,932,240.
The quantity of the particular neoalkoxy compound selected is dependent to a large degree on the proportion of and physical size of the propellant particles being employed, and the chemistry of the additive is determined by the nature of the matrix and effects desired. For example, while the pyrophosphates are found to be outstandingly effective in reducing the burn rate exponent, in urethane systems they produce the side effect of decreasing the cure rate of the resin, which may prove advantageous in large coatings as a means of thermal stress control. The organo-phosphates, on the other hand, have substantially no effect on the cure rate of two component urethanes.
When titanates are used as bonding agents, their catalytic effects on the NCO/OH cure reaction of the propellant binder system can be controlled by treating the aluminum or ammonium perchlorate with a solvent solution of the titanate and subseque
Monte Salvatore J.
Sugerman Gerald
Darby & Darby
Kenrich Petrochemicals Inc.
Miller Edward A.
LandOfFree
Enhanced energetic composites does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Enhanced energetic composites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Enhanced energetic composites will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2522299