GB977309A - Improvements in or relating to combustible pyrotechnic or propellant compositions based on epoxy resins - Google Patents

Abstract

A combustible pyrotechnic or propellant composition comprises (a) as fuel, an epoxy resin which has been hardened with approximately half its weight of organic hardener, (b) sufficient potassium perchlorate for substantially complete combustion of the fuel, and (c) such proportion of a third substance as will ensure ignition and substantially even burning. A small proportion of the potassium perchlorate may be replaced by potassium nitrate. The third substance may be finely-divided carbon, e.g. lamp black. The oxidant is preferably 2-3.5 times the combined weight of epoxy resin and hardener. At the lower end of this range the amount of lamp black used is about 7.5% of the weight of oxidant, and this decreases to about 4.4% when the ratio of oxidant to epoxy resin and hardener is 3.15, and increases to 4.6% at the upper end of the range. A reaction diluent, e.g. butyl glycidyl ether may be added, and is reckoned as part of the epoxy resin. A carbocyclic acid polymerization accelerator may also be added. A number of examples are given of compositions which were filled into a marine distress signal body with a choke formed by a plate having an orifice of 9/64 inch diameter. A conical depression formed in the surface of the propellant facing the orifice plate facilitated ignition. In practice, the resin, hardener, diluent and accelerator were mixed, left to stand for dispersion of air bubbles. Freshly sieved lamp black and oxidant are incorporated in the fluid mass. The mixture, in soft plastic form, is filled by injection into containers, e.g. rocket bodies and left to permit the composition to cure to a hard, waterproof state. Specification 777,840 is referred to.ALSO:A combustible hyrotechnic or propellant composition comprises (a) as a fuel, an epoxy resin which has been hardened with approximately half its weight of an organic hardener (b) sufficient potassium perchlorate to permit substantially complete combustion of the fuel and (c) such a proportion of a third substance as will ensure ignition of the composition and its substantially even burning after combustion. A small proportion of the potassium perchlorate may be replaced by potassium nitrate. The third substance may be finely divided carbon, e.g. lamp black. The preferred range of proportion of the inorganic oxidant is 2-3.5 times the combined weight of epoxy resin and hardener. When the oxidant proportion is at the lower end of this range, the proportion of lamp black is about 7.5% of the oxidant, and this decreases to about 4.4% when the ratio of oxidant to resin and hardener is 3.15:1, and then increases to 4.6% at the upper end of the range of oxidant proportion. To facilitate mixing a reaction diluent, e.g. butyl glycidyl ether may be used. It is regarded as part of the epoxy resin. A polymerization accelerator may also be used with the epoxy resin and hardener. The epoxy resin used in examples was Araldite F-a free flowing product with an epoxide equivalent of 5.1 equivalents/kg. The hardener was Araldite hardener Hy219-a solution of an aromatic amine in a plasticizer. The accelerator was Araldite DY219-a carboxylic acid accelerator. Araldite D which contains dibutyl phthalate may be used if desired. In an example the resin, hardener, diluent and accelerator are mixed and left to stand to allow air bubbles to disperse. Lamp black is sieved and added and then the oxidant. The mixture in soft plastic form is filled into containers, e.g. rocket bodies and left to polymerize. Specification 777,840 is referred to.