Title of Invention

A COMPOSITE PROPELLANT CONTAINING ACTIVE COPPER OXIDE AND A PROCESS FOR PREPARING THE SAME

Abstract

A composite propellant of known polymer, metallic fuel, curing agent , firlely divided ammonium perchlorate and 25% to 1% by weight of active copper oxide obtained by adding stoichiometric quantities of sodium chloride solution to a copper salt solution to precipitate a precLlrsor, which is heated below its reflux temperature to obtain active copper oxide. This inventiorl also includes a process for preparing the composite propellants wherein nown liquid polymers, metallic fuels, ammonium perchorate and the active copper oxide as described in the previous paragraph are mixed to form a homogerleous slurry. This slurry is then cast and heated to produce the propellant.

Full Text

This invention relates to a composite propellant containing application. Hydro thermal production of active copper oxide is carried out by adding stoichiometric quantities of sodium hydroxide solution to a copper salt solution to obtain meta-stable crystals of hydrated precursors containing copper, maintaining the temperature of the reaction mixture below its reflux point to hydrothermally decompose the precursor to precipitate copper oxide which is separated’ washed and dried• Copper oxide prepared according to this technique exhibits exceptionally high catalytic activity due to its higher surface Area It is also found that Marginally lower quantity of this compound is required to impart the desired burn rates when compared to the conventional burn . rate modifier, copper chromate. Lower pressure exponent is also observed in comparison with copper chromite modifier •, Active copper oxide is found to catalyse both low and high temperature decomposition of ammonium perchlorates. Accelerated ageing studies of composite propellants having active copper oxide show that they exhibit very good shelf life without any variation in burning rate values. These facts establish that the propellant envisaged by this invention exhibits unforeseen properties and synergestic action of the components. It is understood that the proportion of the components of the slurry other than active copper oxide is known to persons skilled in the art and needs no special elaboration. The composite propellant according to this invention comprises finely divided ammonium perchlorates, known metallic fuels, polymers, curing agents, and 0.25X to 1% by weight of active copper oxide as burn rate modifier, the said active coppery oxide being produced by adding stanchion metric quantities of sodium hydroxide solution to a copper salt solution, to precipitate meta - stable crystals of hydrated precursors containing copper, maintaining the temperature of the reaction mixture below its reflux point to hydro -thermally decompose, the said precursor to active copper oxide. Hydroxy1 terminated polybutadiene is preferred polymer used in preparing the propellant of this invention. Hydroxy1 terminated polybutadiene having a molecular weight of 2500, polydispersity of 2.0-2.2 and a viscosity of 4000 to 6000 cps at 30 is preferred . The hydroxy1 number may vary from 40 to 46. Ammonium perchlorates may be a bimodal distribution of average particle size of 45 and 300 microns, metallic fuel used may be aluminium powder of the average particle size 15 microns. Characteristic features of active copper oxide in comparison with copper chromite is shown in table I. Table II, III, and IV show candidate propellant formulations, effect of concentration ACO on mechanical and ballistlc properties of HTPB - AP propellant and accelerated ageing data on ACO catalyzed HTPB propellant respectively. From the table* it im clear that the burn rate of the propel lent enhanced up to 377. when up to 0.257. of activated copper oxide is used ‘while 0.5% of activated copper oxide increases it to S6X, whereas addition of 1% of ACQ lowers the rate slightly. Active copper oxide unlike other transition metal oxides, catalyses both the low temperature and the high temperature decomposition of ammonium per chlorate. The amount of acid sites and surface area influence the decomposition of ammonium per chlorate favourably. It is well postulated that during decomposition» the perchloric acid migrates to the catalyst surface by surface diffusion and decomposes there heterogeneously. Active CuO, being a p-type semi conductor, with positive holes in the d-orbitals has the ability to accept electrons from the absorbed HCIO’ thus favoring the decomposition process. When chemisorbed in a surface HCIO’ can interact with electron accepter sites. With increase in pressure, an increase in burning rate is observed. At higher pressure’ the burning rate is controlled by the gas phase reactions occuring due to the high heat release close to the burning surface of the propellant. In the ammonium per chlorate based HTPB propellant, the catalyst acts on HCIO’ or its decomposition products in the gas phase. Naturally at high pressures, more gas phase collision between the catalyst and the oxidizer fragments would occur in the region close to the burning surface. The above explanation justifies the enhanced burning rate and pressure sensitivity of the propellants. The physic-mechanical properties of the cured propellant such tensile strength, elongation, modulus and hardness listed table 3. The mechanical properties of the HTPB propel lent with Active Copper Oxide, the one without burn rate modifier quite comparable as seen from Table 3- The effect of concentration of Active Copper Oxide on mechanical properties shown in Table 3 reveals that the mechanical properties are more or less unaffected by the concentration of Active Copper Oxide. Ageing data has been generated to understand the influence of this burn rate modifier on storage of the propellant and to predict the shelf life of the propellant. Accelerated ageing studies conducted with test specimen of ASTM standard, over a period of 60 days at 60*’ show that there is no marked change in the properties of the Active Copper Oxide catalysed propellant, as seen from Table 4. The accelerated ageing period of 60 days at 60*’C corresponds to an ambient ageing of the propel lant for a period of a|5put 2 years. The mechanical properties show marginal variation, whereas the burning rate values does not show any change with ageing. This shows that the propellant with Active Copper Oxide has good shelf life for any mission application. In view of the above features , the high performance HTPB propel lant containing active copper oxide ill-timed in this invention , is a better potential candidate propellant in rockets and launch vehicle solid motors. Composite propellants according to this invention is prepared by propellant mixing operation in a horizontal sigma or vertical change can mixer. The liquid ingredient are premixed and charged into the mixer followed by the addition of metal 1ic fuel, oxidiser blend and finally the curing agents. The mixing’ operations are continued for a period of 3 hours at ambient temperatures up to 40’C till a homogeneous slurry is obtained. The cast ability of the slurry is obtained by measuring the viscosity at regular intervals of 30mts for a period of 3 to 5 hours. The slurry is then desecrated. and cast into polypropylene cartons as a residual pressure of 3 to 5 torrs. Cast slurry is heated in an oven for an optimum period of 5 days at 60*’C. The oven may be heated by circulated hot water through the same . The mechanical properties and the burn rates of the propellants are then evaluated by known means. The process for preparing a composite propellant according to this invention comprises mixing known liquid polymers metal lie fuels, finely divided ammonium perchlorates and from 0.257. to by weight of active copper oxide obtained by adding stoichiometric amounts of sodium hydroxide to a copper salt solution f maintaining the reaction temperature below the reflux temperature of the reaction mixture to precipitate the said active copper oxide and a curing agent to form a homogeneous slurry , casting and heating the said cast slurry to produce the composite propellant. Clearly9 this invention is not 1imited to the embodiments described and exemplified herein above’ but may be altered or modified in many ways known to persons skilled in propellant research and development without departing from the basic concept thereof . We Claim:- 1. A composite propellant comprising finely divided ammonium perchlorate as oxidizer, known metallic fuels, polymers, curing agents and 0.25X to 1% by weight of active copper oxide as burn rate modifier, the said active copper oxide being produced by adding stoichiometric quantities of sodium hydroxide solution to a copper salt solution to precipitate detestable crystals of hydrated precursors containing copper, fnaintaining the temperature of the reaction mixture below its reflux point to hydro thermally decompose the said precursor to active copper oxide. 2. The composite propellant as claimed in claim 1 wherein the polymer is hydroxyl terminated polybutadiene having a molecular weight of 2500, polydisperity of 2.0 to 2.2 and a viscosity of 4000 to 6000 cps at 60 3. The composite propellant as claimed in any of the above claims wherein, the said ammonium perchlorate has a particle size of 45 and 300 microns. 4. The composite propellant as claimed in claims 1 to 3 wherein the said metallic fuel is aluminium powder of an average particle size of i5 micron. 5. The composite propellant as claimed in any of the above claims wherein the curing agent is a mixture of 2,4 and 2,6 toluene diisocyanate in the ratio of 80/20. 6. The composite propellant as claimed in any of the above claim wherein the said propellant contains known plasticisers cross linking agent©, chain extenders and antioxidants. 7. A process for preparing composite propellant comprising mixing known liquid polymers ^ metallic fuels, finely divided ammonium perchlorate and from 0.25X to IX by weight of active copper oxide obtained! by adding stoichiometric amounts of sodium hydroxide to a copper salt solution, maintaining the reaction temperature below the reflux temperature of the reaction medium to precipitate the said active copper oxide and a curing agent to form a homogeneous slurry casting and heating the said cast slurry to produce the composite propellant. O 8- The process as claimed in claim 7 wherein the slurry is desecrated before casting. 9. The process as claimed c lass 7 and 8 wherein the slurry is cast at a residual pressure of 3 to 5 torso and the cast slurry is heated at 60°c for a period of 5 days. 10. The process as claimed in claim 9 wherein the heating is carried out in ovens having hot water circulated therethrough. i 11. A composite propellant substantially as herein described. 12. A process for preparing a composite propellant

Documents:

241-mas-1997-abstract.pdf

241-mas-1997-claims filed.pdf

241-mas-1997-claims granted.pdf

241-mas-1997-correspondnece-others.pdf

241-mas-1997-correspondnece-po.pdf

241-mas-1997-description(complete)filed.pdf

241-mas-1997-description(complete)granted.pdf

241-mas-1997-form 1.pdf

241-mas-1997-form 26.pdf

241-mas-1997-form 8.pdf