Fluoroalkyl Acrylate Polymeric Propellant Compositions

United States Patent Office 3,255,059 Patented June 7, 1966 1 3,255,059 FLUOROALKYL ACRYLATE POLYMERIC PROPELLANT COMPOSITIONS . Charles L. Hamermesh, .Canoga Park, and Chester F. Makuch, Woodland Hills, Calif., assignors to North American Aviation, Inc. ’ No Drawing. Filed July 9, 1962, Ser. No. 208,642 6 Claims. (Cl. 149-19) Propellant performance is a function of propellant dens_1ty. The importance of propellant density with its effect on the range and payload is exemplified by various volume limited missiles. The direction of past efforts to obtain such high density systems has ben through the replacement of -the oxidizer by more dense ingredients. ThlS' approach has always resulted in severe reduction in specific impulse in the more dense system. Additionally other problems were numerous. For example, the mix- ture of lithium perchlorate and ammonium perchlorate resulted .in propellants which were very diflicult to cast. In an effort directed -to the use of the very high density metals such as zirconium andtitanium, the formulations developed were quite diflicult to cast. Other shortcomings o_f this system were the sensitivity of such propellants, poor combustion efiiciency, and very low delivered im- pulse. Very little effort has been directed to the develop- ment of binders with increased density. This invention concerns novel fluoropolymers. More particularly, the invention pertains to fluoropolymers used as solid propellant binders and additionally is di- rected to a new method for vulcanizing rubber-type com- pounds. An object of this invention is to provide a new solid propellant ‘binder composition. An additional object of this invention is to provide a solid propellant binder ' composition having a high density. A further object of this invention is to provide a solid propellant -binder composition having high stability and thermo-sensitivity. _ ' One other object of this invention is to provide a novel solid propellant formulation. , A still further object of this invention is -to provide a self-curing diolefin polymer. ' . Other objects and advantages will become apparent from the following detailed description. This invention concerns a novel polymeric propellant binder prepared from the reaction of fluoroalkyl acrylate esters selected from the class consisting of 1,l,-dihydro- perfiuoroalkyl acrylate and oa,a,w.-trihydrofluoroalkyl acrylate esters having from two to 11 carbon atoms in the alkyl group and at least one-co-monomer having both an ethylenic linkage and a functional group capable of entering into cross-linking after polymerization. When reacting the fluoro acrylate ester with more than one co- monomer, only one of such co-monomers need possess both the ethylenic linkage and a functional group capa- ble of entering into _cross-linking; the remaining co- monomers need possess only an ethylenic linkage. The number of various co-monomers to be reacted with the fluoroacrylate esters is immaterial and any number can be used so long as the above criteria is met. The proportion by weight percent of fluoroacrylate ester to the other co-monomers, varies from 99:1 to 1:99. A more preferred range of proportions of acrylate to monomer is 50:50 to 95:5. However, since the presence of fluorine is highly desirable, the preferred range of ‘the proportion of fluoroacrylate ester to monomer is 75:25 to 90: 10. It has been discovered that a castable propellant com- position can be_ ‘obtained at 78 percent solids loading if, for example, an 80:20 coarse: chlorate were employed in a solid propellant formulation. Fine‘ ammonium per- ' 5 10 15 20 25 30 40 45 50 55 60 65 70 2 A solid propellant grain can be formulated having from 10 to 40 weight percent of the binder of this invention, from 50 to 85 weight percent of oxidizer and from 0 to 25 weight percent of fuel. Composition containing 62 weight percent of the ammonium perchlorate, 16 weight percent of aluminum, 18.4 weight percent of the novel binder and 3.6 weight percent of a highly-fluorinated sur-_ factant such as fluoroalkyl pyromellitate produces a pro- pellant having a density of 1.95 g./cc. and a calculated impulse -of 258 seconds which is considerably above the current state-of-the-art for high density systems.- The fluoroalkyl acrylate ester utilized in this invention has the following general formula: R1R2O