FR2669626A1 - PROPERGOL COMPOSITION BASED ON NITROCELLULOSE. - Google Patents

Abstract

The invention relates to a propellant composition based on nitrocellulose. This composition comprises a ballistic modifier consisting of zinc oxide, advantageously with one or more conventional ballistic modifiers such as copper or lead compounds, for example lead stearate, lead acetophthalate, β-resorcylate. lead and basic copper salicylate. This composition exhibits good quality plateau combustion over a range of pressures useful for a wide range of combustion rates. Field of application: rocket motors, etc.

Description

The invention relates to a propellant composition based on nitrocellulose

(NC) containing a

  balisti modifier 4 ue to produce the fuel effect

  plateau or mesa on important beaches of

sions.

  The preparation of nitro propellants

  Cellulose is described in Chapter 17 of the book "High Explosives and Propellants" by S Fordham, Second Edition Pergamon Press 1980. The manufacture of a propellant cast with nitrocellulose and nitroglycerine is also described in British Patent No. 827,012 and

No. 1,095,471.

  In general, for a given ignition temperature, the burning rate of a propellant in

  a combustion chamber is related to the pressure at

  which the propellant is exposed in a way that can be expressed mathematically by the expression r = kpn where r is the rate of combustion, p is

  the pressure and k and N are characteristic constants

  Thus, R exponentially increases with p and log r linearly increases with log p, the log r curve as a function of log p being a slope line n In a conventional propellant without a ballistic modifier, the pressure exponent N has a value

  from 0.5 to 0.8 and, for the propulsion of a rocket, the elevation

  Increasing pressure with increasing pressure is causing problems in engine design to withstand the pressures that can be developed. To solve this problem, nitrocellulose-based propellant compositions containing ballistic modifiers have been developed. the modifier having the effect of modifying the relationship between the burning rate and the pressure so that, over a useful range of working pressures, the pressure exponent n is reduced In the region on = o, the log-in curve r log p function contains a flat part,

  called "plateau", and combustion is called "combus-

  In some cases, N is lowered to a negative value over a certain range of pressures,

  this combustion of propellant being then called "com-

  mesa bombardment "Ballistic modifiers causing a decrease in the pressure exponent are called platinizing agents Platel burning propellants reduce the variability of engine performance in the plateau region and mesa combustion.

  provides additional security against the development

  high pressure in the propellant container.

  Commonly used ballistic modifiers (platinizing agents) include organic salts such as lead salicylate, lead stearate or lead B-resorcylate, and

  may also include additional metal salts

  Examples of such ballistic modifiers are described, for example, in U.S. Patents Nos. 3,088,858 and 3,923,564, US Pat. in British Patent No. 2,121,399

  and in Japanese Patent No. 55071690 For proper

  As relatively fast-burning gols, a preferred modifier comprises the reaction product of β-lead resorcylate and basic cupric salicylate as described in the United States patents.

  Nos. 3,138,499, 3,994,757, 3,989,776 and 4,001,287.

  The ballistic modifiers currently used are deficient in certain aspects. Thus, the platonized propellant compositions often have poor reproducibility of the tray characteristics from one batch to another, chemical instability in long-term storage, combustion instability. and a ballistic drift in storage So we need propellant compositions

  ballistic modifiers, in particular

  bind high-energy, fast-burning, well-platonized compositions containing, when necessary,

  of aluminum or high levels of energy

  such as a nitramine, for example RDX (cyclo-

  1,3,5-trimethylene-2,4,6-trinitramine). It has now been discovered that nitrocellulose propellants with enhanced plateau or mesa combustion characteristics can be obtained by the use of a ballistic modifier comprising zinc oxide. This modifier provides good quality plateaux. which are reproducible from one batch to another and the modified propellants do not undergo

  no ballistic drift in storage.

  Zinc oxide, in itself, is a modification

  effective ballistic indicator for nitrocellulose propellants, including a cast propellant and a

  extruded propellant based on nitrocellulose and nitro-

  glycerin, but it is advantageously used with

  other ballistic modifiers such as B-resor

  lead cylate and lead salicylate to improve

  the platonic burning rate With such modifications

  Mixed Ballistic Factors, Burn Rate

  platonized propellant can be "adapted" to the requirements of

  particular rocket engine and the rate of combustion, even burning-rate propellants

  high, can be increased, in some cases by 19%.

  Modified propellants have improved chemical stability, as reflected in the better results obtained in the cracking test. This can be attributed to a reaction between zinc oxide and

  impurities of protic acids present in the

  propellant, which, in the absence of

  zinc, cause degradation of the nitric esters.

  It has also been discovered that incorporation

  of zinc oxide as a modifier in proper

  Nitrocellulose attenuates or eliminates the instability of combustion that is caused by acoustic resonance waves that accumulate in a rocket engine cavity during propellant combustion and cause large fluctuations in pressure / time characteristics. The improvement seems to be attributable to zinc oxide, because of its high melting point, which zinc oxide behaves like

a resonance suppressor.

  Thus, according to the invention, a composition

  nitrocellulose propellant coating includes

  zinc oxide as a ballistic modifier.

  Preferred compositions comprise a mixture of zinc oxide and one or more of the lead compounds or

  effective copper as a ballistic modifier.

  Suitable lead and copper compounds for this purpose include lead stearate, lead citrate,

  lead phthalate, lead acetophthalate, saline

  lead cylate, lead B-resorcylate, basic copper salicylate, copper B-resorcylate and oxide

of copper.

  The propellant compositions of the invention

  advantageously contain from 2 to 8.0% by weight of

  and when the modifier comprises a lead or copper compound assuming the function of a ballistic modifier with zinc oxide, the composition should advantageously contain from 0.15 to 0% by weight of zinc oxide.

  In addition to nitrocellulose and modification

  ballistic material, the propellant compositions of the invention

  may contain conventional propellant ingredients, including nitroglycerin (in nitrocellulose and nitroglycerin propellant);

  stabilizers, for example para-nitro N-methyl-

  aniline, 2-nitrodiphenylamine or resorcinol; plasticizers, for example saccharide octoacetate;

  rose, triacetin or dibutyl phthalate; constitutions

  energy killers, for example a nitramine such

  RDX or a powdered metal such as aluminum

  minium; moderators of combustion rate, for example carbon black; lubricants, for example candelilla wax; polyneric binders,

  for example a cross-linked polycaprolactone with an iso-

  cyanate; spark suppressors, for example potassium nitrate, and resonance suppressors,

for example silicon carbide.

  The platonized propellant compositions of the invention can vary over wide ranges of energy and vitessec of combustion.

  formulate a useful composition covering the energy range

  range from about 3350 J / g to 5000 J / g and speeds

  of combustion ranging from about 4 mm / s to about 45 mm / s.

  The composition can be prepared by the conventional methods

  appropriate propellant production

  respective nitrocellulose propellants.

  The invention is further illustrated by the following examples in which all percentages

are given by weight.

  The examples concerned batches of products

  pergol having the compositions shown in the table, prepared by conventional methods of producing propellants, as described in chapter 17 of the book "High Explosives and Propellants", by S Fordham, second edition Pergamon Press 1980 Except zinc oxide, the ingredients used were constituents of

propellants commonly used.

  Examples 3-6 were cast propellants based on nitrocellulose and nitroglycerin produced by a conventional method in which a powder of such propellant containing most of the ingredients was prepared by a solvent incorporation process. and then mixed with a casting liquid containing

  about half of the nitroglycerin

  Acetin and part of the stabilizer For the combustion velocity test, platelets and end-of-combustion charges were cut from the cast propellant.

  that was burned in an engine at an initial temperature

  21 VC (unless otherwise indicated).

  Examples 1 and 2 used the solvent method. The propellant of these examples was extruded into rods 2 mm in diameter × 18 cm in length which received a surface inhibition treatment with

  vinyl lacquer so that it remains a constant surface

  end of combustion Combustion speeds

  chopsticks were measured over a range of pres-

  while the chopsticks were burned from the untreated extreme surface into a Crawford drumstick combustor under a nitrogen atmosphere and at an initial

21 VC (unless otherwise indicated).

EXAMPLE 1

  This example was an extruded, solvent-based, platonized propellant composition based on nitrocellulose and nitroglycerin, containing 4.00%

  of zinc oxide as the only ballistic modifier.

  The ballistic properties (rate of combustion as a function of pressure) are shown graphically in FIG. 1 in the form of a curve giving,

  on logarithmic scales, the fuel velocity

  The curve shows that zinc oxide gave a plateau

  18 mm / s under a pressure of 175-225 105 Pa.

EXAMPLE 2

  This example was an extruded, solvent-based, platonized propellant based on nitrocellulose and nitroglycerin, having the same composition as that of Example 1, except that the ballistic modifier consisted of 2.0% zinc oxide. The results of the ballistic test of this composition, shown graphically in FIG. 2, indicate that this composition exhibited a plateau combustion at a higher rate of combustion, of about 27 mm / s, over a range of pressures

about 85-200 to 105 Pa.

  EXAMPLES 3 (a) and 3 (b) These examples were cast, platonized propellants based on nitrocellulose and nitroglycerin, having substantially the same composition except that the propellant of Example 3 (b) contained 0.34. % zinc oxide in addition to 1.99% B-resorcylate

  lead and 1.99% lead salicylate as a

  The results of the ballistic test of these compositions are shown graphically in Figure 3 These results show that zinc oxide produced a higher plateau of combustion rate

  over an increased pressure range of about 80-175 105 Pa.

  60 ° C was stored for 12 weeks

  platelets of these compositions and we again

  the burning velocities of the propellant of the

  pl (3) showed a downward ballistic drift of 7% over the storage period, whereas that of Example 3 (b) showed practically no variation in ballistic characteristics, which shows the effect of zinc oxide to prevent downward ballistic drift usually attributed to a reaction between the lead B-resorcylate and the salicylate of

lead in the composition.

EXAMPLE 4

  This example was about a composition

  propellant cast, platonized, modified by an elastic

  tomato based on nitrocellulose and nitroglycerine, containing 0.66% zinc oxide, 1.98% lead B-resorcate, 1.98% lead salicylate and 3.53% polymeric binder consisting of a polycaprolactone cross-linked with an isocyanate The combustion rates, tested at initial temperatures of -40, 21 and 60 C, were 25-25 m / s in each case, over a platonized combustion range of 100. -175 105 Pa, as

shown in Figure 4.

  The burning rate did not vary much with the initial temperature (i.e., the temperature coefficient was low) on the

  range from -40 to 60 C in the plateau combustion region.

  EXAMPLES 5 (a) and 5 (b) These examples related to propellants

  cast, platonized, loaded with aluminum, nitro-

  cellulose and nitroglycerin, having substantially the same composition, except that the propellant of Example (b) contained 0.34% of zinc oxide. Cubes of 1 cm side, consisting of the two compositions, have

  stored at 80 C and subjected to an examination (by radiogra-

  phie) to detect signs of cracks or

  internal defects The propellant of Example 5 (a)

  cracks after 8 days, whereas

  Example 5 (b) showed no signs of cleavage.

  or cracking before 21 days.

EXAMPLE 6

  This example involved a high-energy, nitrocellulose and nitroglycerin-based, high-platinum elastomer-modified propellant containing 0.21% zinc oxide, 3.21% polymeric binder (similar to the one used in Example 4), 19.6% of RDX and 1.4% of silicon carbide. The results of the ballistic test, shown in FIG.

  a plateau combustion at about 20 mm / s, with a coef-

  ficient of acceptable temperature (low), over the pressure range of 80-150 105 Pa.

BOARD

  position 1 2 3 (a) 3 (b) 4 5 (a) 5 (b) 6 Nitrocellulose 40.50 40.50 40.09 39.89 26, 47 35.57 35.40 21.15

(12.6% N)

  Nitroglycerin 46.86 46.86 47.12 47.01 56.50 43.75 43.64 44.74

p-nitro-N-methyl-

  aniline 0.7 0.7 0.67 0.66 0.66 0.60 0.60 0.69

2-nitrodiphényl-

  amine 0.3 0.3 0.33 0.33 0.33 0.33 0.33 0.30 Triacetin 7.44 7.44 7.59 7.59 7.69 7.44 7.44 6.09 Zinc oxide 4.00 2.0 0.34 0.66 0.34 0.21 Carbon black 0.2 0.2 0.2 0.2 0.2 1.14 1.13 0.11 o B - lead resorcylate 2.0 2.0 1.99 1, 98 4.02 4.0 1.25 Lead salicylate 2.0 1.99 1.98 1.25 Polymeric binder * 3.53 3.21

Aluminum 4,56 4,54 -

Copper salicylate

basic 1.94 1.93 -

Resorcinol 0.65 0.65 -

RDX _ 19.6

Silicon carbide

  cium 1.4 TABLE (Continued) Preparation process Platonized burn rate (mm / s) Extruded pressure range (x 105 Pa)

on the ground-

extruded

on the ground-

efore

-225 85-200

  casting casting casting casting casting

-130 80-175 100-175

  -150 Longevity before splitting (days

at 800 C)

  Polycaprolactone crosslinked with isocyanate.

O% O% M O O% O%

Claims (4)

  1 Propellant composition based on nitro-   cellulose, comprising a ballistic modifier,   characterized in that the ballistic modifier comprises zinc oxide   2 Propellant composition according to the   1, characterized in that the ballistic modifier comprises a mixture of zinc oxide and one or more lead or copper compounds which are   effective as a ballistic modifier of ben.   3 Propellant composition according to the   2, characterized in that said lead and copper compound comprises lead stearate,   lead citrate, lead phthalate, acetonitrile   lead phthalate, lead salicylate, B-resorate   lead cylate, basic copper salicylate,   B-copper resorcylate or copper oxide.   4 Propellant composition according to one   any of claims 1 to 3, characterized in that   what it contains from 2 to 8.0% by weight of ballistic.   Propellant composition according to Claim 4, characterized in that it contains 0.15 to 5.0% by weight of zinc oxide.   6 Propellant composition according to one   any of claims 1 to 5, characterized in that   what it includes a stabilizer, a plasticizer, a moderator of combustion rate, a lubricant and / or a spark suppressor.   7 Propellant composition according to the   6, characterized in that it comprises   para-nitro-N-methylaniline, 2-nitrodiphenyl-   amine, resorcinol, sucrose octoacetate, triacetin, dibutyl phthalate, carbon black, candelilla wax, cross-linked polycaprolactone   with isocyanate, potassium nitrate or car- Silicon bure.   8 Propellant composition according to one   any of claims 1 to 7, characterized in   it contains at least one energy constituent, such as a powdered metal or a nitramine, for example   cyclo-1,3,5-trimethylene-2,4,6-trinitramine.   9 Propellant composition according to one   any of claims 1 to 11, characterized   in that it has an energy in the range of 3350 to 5000 J / g.   Propellant composition according to one   any of claims 1 to 11, characterized   in that it has a burning speed of 4 to 45 mm / s.