Nitropolymers

For a discussion of these type compds see Ref 12. The chemistry and technology of DNMe has been reviewed in Ref 9 with emphasis on its use as an intermediate for the prepn of nitropolymers, especially thru 2,2-dinitro-1,3-propanediol (code name A-diol)... 

R.D. Geckier, Research in Nitropolymers and their Application to Solid Smokeless Propellants , AerojetEngrgCorp, Azusa,. Calif, Quarterly Report 345, Contr No N7-onr-462 (4 Jan 1949),... 

The selected nitropolymers in this article are presented alphabetically with respect to their polymeric designation, viz, (poly) acrylate, (poly) amide, (poly) ester, etc. Each of these polymeric types is defined in each entry by graphic formula. The sole amide and polyester discussed... 

Refs 1) L.H. Brown R.D. Geckler, Research in Nitropolymers and Their Application to Solid Smokeless Propellants", Report No 345, Aerojet Engrg Corp, Azusa, Calif, ONR contract N7 onr-462, Task Order 1 (4 Jan 1949), 7—13 2) P.J. Blatz et al, Research... 

Of the many nitropolymers devised as pro-pints by Aerojet General Corp, one regular and one post nitrated polyurea polymer resulted which can be considered expls and are presented below ... 

The postnitrated polymer has a Qc of 2716 cal/g (Ref liq H20 at 25°), an impact sensy at the 50% point of 85cm using a BM machine with 2kg wt (RDX, 28cm), and a rel vise of 1.5 centipoises at 25° using a 2% acet soln Refs 1) PJ. Blatz et al, Research In Nitropolymers And Their Application To Solid Smokeless Propellants , Report No 638, Aerojet-General Corp, Azusa, Calif, ONR Contract N7 onr462. Task Order I (7 Oct 1952), 33 39 2) Ibid, Report No 1162 (28 Sept 1956), 184... 

Nitro Allyl Acetate. See under Nitropolymers , in this Vol... 

Chlor-1-Nitro-Ethylene and Polymer. Sfee in this Vol. under Nitropolymers ... 

Nitropolymers and Their Application to Solid Smokeless Propellants , Report No 1241, Contract N70nr-462, Aerojet-General, Azusa (1957) 4) D.B. Bright, Development of... 

K. Banm, V. Grakanskas, E. E. Martin and N. W. Thomas, Research in Nitropolymers and their Application to solid Propellants , Report 1877, Oct 13, I960, Contract Nonr-2655(00), Available from Defence Technical Information Center, Cameron Station, Alexandria, VA 22304-6145. 

NC is an energetic nitropolymer consisting of a hydrocarbon structure with -O-NO2 bonds as oxidizer fragments. In general, NC is produced from the cellulose, C6H702(0H)3 j of cotton or wood, which is nitrated using nitric acid (HNO3) to introduce -O-NO2 bonds into its structure. 

The physicochemical properties of explosives are fundamentally equivalent to those of propellants. Explosives are also made of energetic materials such as nitropolymers and composite materials composed of crystalline particles and polymeric materials. TNT, RDX, and HMX are typical energetic crystalline materials used as explosives. Furthermore, when ammonium nitrate (AN) particles are mixed with an oil, an energetic explosive named ANFO (ammonium nitrate fuel oil) is formed. AN with water is also an explosive, named slurry explosive, used in industrial and civil engineering. A difference between the materials used as explosives and propellants is not readily evident. Propellants can be detonated when they are subjected to excess heat energy or mechanical shock. Explosives can be deflagrated steadily without a detonation wave when they are gently heated without mechanical shock. 

Molecules in which fuel and oxidizer components are chemically bonded within the same structure are suitably predisposed for the formulation of energetic materials. Nitropolymers are composed of O-NO2 groups and a hydrocarbon structure. The bond breakage of O-NO2 produces gaseous NO2, which acts as an oxidizer fragment, and the remaining hydrocarbon structure acts as a fuel fragment. NC is a typical nitropolymer used as a major component of propellants. The propellants composed of NC are termed nitropolymer propellants . 

Since the energetics of nitropolymer propellants composed of NC-NG or NC-TMETN are limited due to the limited concentration of oxidizer fragments, some crystalline particles are mixed within these propellants in order to increase the thermodynamic energy or specific impulse. The resulting class of propellants is termed composite-modified double-base (CMDB) propellants . The physicochemical properhes of CMDB propellants are intermediate between those of composite and double-base propellants, and these systems are widely used because of their great potential to produce a high specific impulse and their flexibility of burning rate. 

When crystalline AP particles are mixed with nitropolymers, ammonium perchlorate composite-modified double-base (AP-CMDB) propellants are formulated. A nitropolymer such as NC-NG or NC-TMETN double-base propellant acts as a... 

The reaction rate is seen to increase linearly in an In [mj versus In p plot, and the overall order of the reaction in the gas phase is determined to be m = 1.78 based on the relationship m=n- d. This indicates that the reaction rate of TAGN in the gas phase is less pressure-sensitive than that of nitropolymer propellants for example, m = 2.5 for double-base propellants.PS]... 

This reduction of NO is highly exothermic but relatively slow at low pressure, because it appears to be a third-order reaction, similar to the dark-zone reaction of nitropolymer combustion. The overall reaction of HNF is represented by... 

The combustion of H2, CO, and hydrocarbons with NO is important in both the dark zone and the flame zone of nitropolymer propellants. It is well known that NO behaves in a complex way in combustion processes, in that at certain concentrations it may catalyze a reaction to promote a process, while at other concentrations it may inhibit the reaction. Sawyer and GlassmanP attempted to estabUsh a measurable reaction between H2 and NO in a flow reactor at 0.1 MPa. Over a wide range of mixture ratios, they found that the reaction did not occur readily below the temperature of NO dissociation, except in the presence of some radicals. Mixtures of CO and NO are also difficult to ignite, and only mixtures rich in NO could be ignited at 1720 K. 

In summary, gas-phase reactions between aldehydes and NOj occur readily and with strong exothermicity. The rate of reaction is largely dependent on the alde-hyde/N02 mixture ratio, and is increased with increasing NO2 concentration for aldehyde-rich mixtures. On the other hand, no appreciable gas-phase reactions involving NO are likely to occur below 1200 K. The overall chemical reaction involving NO appears to be third order, which impUes that it is sensitive to pressure. The reactions discussed above are important in understanding the gas-phase reaction mechanisms of nitropolymer propellants. 

Table 6.12 Chemical compositions of nitropolymer propellants catalyzed with KNO3 and K2SO4.

Fig. 7.46 shows the burning rates of the catalyzed HMX propellants and demonstrates a drastically increased burning rate, i. e., super-rate burning. However, LiF or C alone are seen to have little or no effect on burning rate. The super-rate burning occurs only when a combination of LiF and C is incorporated into the HMX propellant. The results indicate that LiF acts as a catalyst to produce super-rate burning of the H MX propellant only when used in tandem with a small amount of C. The C (carbon black) is considered to act as a catalyst promoter. A similar superrate burning effect is observed when the same catalysts are added to nitropolymer propellants. 

HMX composite propellants are composed of crystalline HMX particles and polymeric materials, and so their physical structures are heterogeneous. On the other hand, nitropolymer propellants are composed of mixtures of nitrate esters such as NC and NG, and their physical structures are homogeneous. Moreover, HMX pro-... 

It is well known that the super-rate burning of nitropolymer propellants diminishes with increasing pressure in the region 5-100 MPa and that the pressure exponent of burning rate decreases. - ] This burning rate mode is called plateau burning. As for these nitropolymer propellants catalyzed with LiF and C, HMX propellants catalyzed with LiF and C also show plateau burning. 

The combustion wave structure of HMX propellants catalyzed with LiF and C is similar to that of catalyzed nitropolymer propellants the luminous flame stands some distance above the burning surface at low pressures and approaches the burning surface with increasing pressure. The flame stand-off distance from the burning surface to the luminous flame front is increased at constant pressure when the propellant is catalyzed. The flame stand-off distance decreases with increasing pressure for both non-catalyzed and catalyzed propellants. 

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