US2440327A - "hot" double-base powder - Google Patents

Description

Patented Apr. 27, 1948 UNIT'D S" "S HOT. DOUBLE=BASEQPOWDER Minnesota No Drawing. Application December 29, 1943, Serial No. 516.081

This inventionrelatesto explosives and more particularly to propellants of the so-called =hoir, double-base powder types, whereindiificulty has heretofore been encountered due-to ignitionby radiation and fissuring during the use- Of' thick powder sections. The=unstableburning charaoe teristics of such double-base powders has been found to be-induced by-the-formation'of minute holes, described in thetrade as fissures or wormholes, in the interiorof-thepowder grain during burning, and'suoh characteristics have a serious deterrent to the use-of this typeofipowders-i'nj et-propulsion motors; projectiles and the like.

When intense radiant energy radiationsimpinge upon powder, ignition occurs; and-this-is efiected by any fissure or crack in the powder section, or bit of dust, or .other irregularity. Where there is an irregularity-or bit of dust, the first efiect is a local accumulation of" radiant energy, which then'causes a minute cavity'having the appearance of a fissure orwormhol'e. If the radiant energyis continued, the energy accne mulation at the irregularity; fissure or"wormhole continues until'ignitiontakes place. Buming may thus be initiated at'many places nearly simultaneously inasingle large sectiorrof powder: This is most unsatisfactory and frequentlywery dangerous where'thepowder is used. as thepropellant in a jet propulsion device such.as a rockettype proj ectile;

In order to overcome this difiiculty; it has heretofore been proposed to render'the powder opaque by inclusion of a small" amount oflopaque substance such as carbon black or nigrosine or by inclusion of diphenylamine, subsequentlydarkened by exposure to heat or sunlight. Suchpowders have satisfactory burning, characteristics and appear to be less susceptible to-iissuring possibly because of lower flame temperatures. but they areseriously deficient in that examination of the interior of the: otherwise. clear powder grain by visual. inspection; using; transmitted light, is rendered impossible insuch opaque pow.-

ders.

It is an object of thepresentinvention to; pro;- vide an improved: propellant; specifically an im'.- proved double-base powder capable of being visually.- inspected: and yet. having satisfactory 4 Glaims. (CI. 52-13) 2: burning characteristics and'free fromvthe difliculties of 7worming..

It'is alsoan-object of the invention to provide an improved explosive capable of. such clarity as toallow visual inspection through large sections by utilizing transmitted: light andcontainin a substance capable of substantially diminishing the worming and ignition byradiation.

Other and further objects of .the invention are those inherent in the following description and claims.

In carrying out the invention there is preferably usedi any suitable explosive, preferably a double-base powder such as Trench mortar type: Percent Nitrocellulose (13.25% nitration) 51.5 Nitroglycerin 4310 Ethyl centralite' 4.0 Potassium nitrate; 1.5

Modified bullseye type: Per cent Nitrocellulose (13.25% nitration) 59.0

Nitroglycerine 40.0 Ethyl centralite 1.0

These explosives exhibit the worming eflect, ignition by radiation. and fissuring effects, and haveaunsatisfactory'characteristics when used in large solid sections for jet propulsion devices such.asrocketiprojectiles. To the selected explosive there is added a small percentage of: pigment or'dye,.or substance capable of being developed into" a; dye,v this additionbeing preferably made at the-timezthaexplosiveisbeing made, and while it? is in afreelyplastic or'fluid. stage, such that the. pigment. or.- dye may be evenly distributed throughout: the powder by milling or working. The admixture of thecol'oring material.- may be effected at any time during manufacturing,- for exampleafter the-nitrocellulose and nitroglycerin of the powder are mixed. Thus, admixture of the coloring. matter may be made during the colloiding step of the usual powder-making. procedure. .IThe pigment. or dye is applied either dry'ori'n asuitable solvent or carrier compatible with. the: powder while. mixing.

Fonthe-pigmentor dye thereis used. any color! ing compound having a high radiantener-gyabsorption coeflicient in the wave length range of .8 to 5.0 ,u, capable of passing visible light and which is stable in the powder and does not adversely affect the stability of the powder. The pigment or dye (herein sometimes collectively referred to as coloring material) may either be a soluble coloring material or of colloidal character such that it is capable of being evenly dispersed or dissolved in the powder. The coloring material must not be of such a type as will preclude passage of sufficient light through the powder section for visual inspection of the section and must be stable in the powder, and must not adversely affect the stability of the powder.

As examples of suitable pigments or dyes there may be mentioned copper chloride, Prussian blue, methylene blue, ferric chloride, Luxol green, nitro-sodium methylaniline, chromium chloride, Cyanine XXXIX (1,1-diethyl-4,4'-tricarbocyanine iodide), p-nitroisodiphenylamine. All of these materials exhibit some improvement,

though certain of the pigments, notably Prussian blue, copper chloride and methylene blue exhibit Table A.Actz'm'ty of representative coloring agents in HES 4021 powder Activity Coloring Agent Percent (0.104 cm.

per calorie) CIICIZ'ZHZO 1.00 0.70 D 0. 4O 61 Prussian blue. 0.05 .52 Methylene blu 0.10 .41 FeCl 1. O0 34 LuXol green. 0. 10 .28 Nitro-sodium methylanilinc. 0. 10 25 ClCla-GHzO 1. 0O 24 Cyanine XXXIX (l,l-diethyl-4,4'-tricarbocyanine iodide) p-Nitroisodiphenylamine 0. 05 23 p-Nitroisodiplienylamine O. 21 Methylene blue l 0. 01 21 Plain cast powder section .r Plain sheet powder section 15 The foregoing examples illustrate the range of concentration of coloring matter, so as to yield a powder in which radiant energy between the wave lengths of .8 to 5.0 a is largely absorbed, but in which sufficient Visible light is transmitted to allow visual inspection of slabs up to several inches in thickness for cracks, fissures, bubbles, specks, etc.

When ignition time for a given sample of powder is plotted as a function of the intensity of incident radiation, the plotted points fall on a hyperbolic curve. While a comparison of the activity of different basic powder compositions, or containing for example different coloring materials, can be made from such curves, a more convenient method of comparison is to plot the reciprocal of the ignition time as a function of light intensity. When this is done a straight line results. This is supported by the following approximate analysis:

Powder will ignite when it has accumulated a quantity of energy Q1 sufiicient to reach the ignition temperature. The increment of energy dQ accumulated per unit area of incident surface in time dt will be where I is the intensity of incident radiation, In is proportional to the fraction of light absorbed by the sample and k2 is the rate of energy loss from a unit area at the powder surface and so will be dependent on t. However, as a first approximation one may consider the 'average value k2 between the initial time to and the time of ignition ii to be a constant for any given powder. Then, when ignition occurs The quantity Qi is nearly constant for a given basic powder and varies only slightly for small changes in powder composition, such as the addition of dyes and pigments; In is an effective overall absorption coefiicient which will be strongly influenced by any coloring agent placed in the powder.

The slope Far/Q1 of the straight line obtained from the plotting of the reciprocal time versus radiation intensity, according to (3) may be taken as an indication of the activity of a given powder toward light of a given wave length range. The relative effectiveness of the several powder compositions listed in Table A are thus able to be compared conveniently.

The foregoing analysis is presented as an aid in understanding the invention but is not intended as a limitation thereon.

As many apparently widely diiferent embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiments herein except as defined by the appended claims.

What I claim is:

1. A thick section of double-base powde of the hot type that is normally susceptible to worming in the presence of intense radiations developed during burning, said powder being colored with a coloring matter capable of absorbing radiant energy in the wave length range of .8 to 5.0 ,u, said coloring matter being of a type and present in an amount such that visible light is capable of being transmitted through the powder, thus permitting visual inspection thereof, and present in an amount such that radiations between the wave lengths of .8 to 5.0 are largely absorbed.

2. A thick section of double-base powder of the hot type that is normally susceptible to worming in the presence of intense radiations developed during burning, said powder being colored with copper chloride, said copper chloride being present in the powder in an amount such that visible light is capable of being transmitted. through the powder, thus permitting visual inspection but present in an amount such that radiations in the wave length range of .8 to 5.0 c are largely absorbed.

3. A thick section of double-base powder of the hot type that is normally susceptible to 5 radiations in the wave length range of .8 to 5.0 ,u are largely absorbed.

4. A thick section of double-base powder of the hot type that is normally susceptible to worming in the present of intense radiations developed. 5

during burning, said powder being colored with methylene blue, said methylene blue being present in the powder in an amount such that visible light is capable of being transmitted through the powder, thus permitting visual inspection but present in an amount such that radiations in the wave length range of .8 to 5.0 ,u are largely absorbed.

BRYCE L. CRAXVFORD, JR.

REFERENCES CITED The following references are of record in the file of this patent:

OTHER. REFERENCES Marshall-Explosives, vol. I, Phila., 1917, pages 15 323, 326 and 329. (Copy in Div. 43.)

Certificate of Correction Patent N 0. 2,440,327. April 27, 1.948.

BRYCE L. CRAWFORD, JR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, Table A, first column thereof, in the ninth item under the heading Coloring Agent, after iodide) strike out "p-Nitroisodiphenylamine; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 22nd day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant G'ommissioner of Patents.

Certificate of Correction Patent No. 2,440,327. April 27, 1948.

BRYCE L. CRAWFORD, JR.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, Table A, first column thereof, in the ninth item under the heading Coloring Agent, after iodide) strike out p-Nitroisodiphenylamine";

and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 22nd day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.