What is a Propellant?

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2 What is a Propellant? A propellant is a material that produces pressurized gas that fills the interior of an ammunition cartridge or the chamber of a gun or cannon, leading to the expulsion of a bullet or shell (gunpowder, smokeless powder, and large gun propellants). Rockets also use propellants for their motion.

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4 Introduction Nitrocellulose is obtained from cellulose and nitric acid. All given sample of cellulose contains a wide distribution of molecules, all having the empirical formula of [C6H7O2(OH)3]n Cellulose nitrate (nitrocellulose) is a nitric acid ester used in explosives as a propellant. It is also known as guncotton or nitro cotton.

5 Pure Cellulose Nitrate is yellowish white cotton-like filaments

6 Uses Cellulose nitrate has to be the most important ingredient in the explosives field. It is the basis for most propellants, many rocket propellants and the foundation for countless commercial blasting explosives.

7 Chemical Reaction C6H7O2(OH)3 + 3HNO3 C6H7O2(NO3)3 + 3H2O

8 Sources of Cellulose Cotton Wood fiber

9 Process Chemically the reaction itself is an esterification and not a nitration. Nitrocellulose with a very high degree of esterification (nitrogen content higher than 12.6 %) is used as gun cotton. It is proper to use the name cellulose nitrate rather than nitrocellulose because the reaction is an esterification but not nitration reaction.

10 Purification of raw material Bleaching Nitration Acid separation Pressure boiling Beating Poaching Steps Involved in Process Dehydration and Alcoholization Formation of granulars

11 Purification: Raw cotton linters and wood fibers are boiled with NaOH to purify the cellulose present in it. Bleaching: Removal of undesired colors. Nitration: One nitrator charge is formed by 14.5 kg of purified cellulose. The cellulose is agitated with approximately 682 kg of mixed acid at 30 o C for about 25 min. the composition of acid used averages HNO3 21%, H2SO4 63%, N2O4 0.5%, H2O 15.5%. C6H7O2(OH)3 + 3HNO3 C6H7O2(NO3)3 + 3H2O All the cellulose is converted to Cellulosenitrate in the nitrator because the amount of acid is very high and this acid does not leave any cellulose unconverted. Acid Separation: After nitration, the nitrocellulose is separated from the spend acid in the centrifuges and nitrocellulose produced is sent to next part of the plant.

12 Pressure boiling: The cellulose nitrate is boiled and washed with water to remove H2SO4 present. Beating: Now CN is finely pulped and washed again in a beater. Na2CO3 is also added to neutralize any remaining acid. Poaching: This CN is again washed in a poacher at boiling condition. The purpose of poaching is to decompose the sulphate esters produced and removal of salt and CO2 produced in the beater. H2SO4+Na2CO3 Na2SO4+H2O+CO2 (The acid remaining in the product became the cause of some of the nasty explosions in propellant factories in the late 1800s). Dehydration and Alcoholization: Alcohol is added to replace the water present. Formation of granulars: The nitrated cellulose is broken up and made into a dense colloid by mixing with alcohol, ether, diphenylamine and other modifying agents.

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14 Nitrogen Content Nitrocellulose with a very high degree of esterification (nitrogen content higher than 12.6 %) is used as gun cotton. nitrocellulose with a nitrogen content of between 10.7 % and 12.3 %. This is used as a binder in printing inks and coatings. Modern military smokeless powder contains about 13.15% of nitrogen.

15 Why nitrogen content is important in explosives? Nitrogen gas, N2, is a very inert, stable gas; it is two atoms connected by a triple bond. The delta-h of formation of N2 gas from two nitrogen atoms is about -950 kj which means it gives off a LOT of energy! So explosives have nitrogen atoms in them and the more nitrogen atoms that are available to come together and form N2 gas, the more energy will be released, the bigger the boom!