Nitrocellulose

Nitrocellulose[18] (also: cellulose nitrate, flash paper) is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton.

Properties:
OTHER NAME: cellulose nitrate, flash paper
MOLECULAR FORMULA:
[C6H7O2(OH)3-r(ONO2)r]n
SHOCK SENSITIVITY: High
FRICTION SENSITIVITY: High
EXPLOSIVE VELOCITY: 7100 m/s

For many centuries gunpowder was the world's only explosive, and was not superseded until the discovery of guncotton. So long ago as 1832 Bracon discovered that woody fiber could be turned into an explosive by the action of concentrated nitric acid; and a few years later a French inventor, Dumas, tried to make cartridges of paper treated in similar fashion. If he had succeeded these would have been the first smokeless cartridges, but he failed; and it was not until 1845 that Schšnbein, a German chemist, hit upon the proper method of treating cotton wool with nitric and sulphuric acids, so as to turn it into guncotton.
In 1847 an English firm, Messrs. Hall and Son of Faversham, began to manufacture guncotton, and military experts hailed it as the new explosive which would take the place of gunpowder. But this explosive was so terribly powerful that, when used in a gun or rifle, it blew the barrel to pieces. Worse than that, it was most dangerous to manufacture.
Two main problems had to be solved before it could be used as a gun propellant. First, the velocity of the explosion had to be reduced so that the charge weight required to propel the projectile would not shatter the gun tube. Second, the density had to be increased so that a given charge weight would pack into a reasonable space. The first problem was solved in part by igniting nitrocellulose instead of firing it with a detonator. The solution to the second problem actually solved both. In 1886, Vielle first colloided or gelatinized nitrocellulose with alcohol and ether and, thus reduced the burning rate to acceptable levels. The procedure significantly increased the loading density of nitrocellulose, establishing it as the foundational element in gun propellants used through the present day.
The process uses the nitric acid to convert the cellulose into cellulose nitrite and water:
3HNO3+ C6H10O5 --> C6H7(NO2)3O5 + 3H2O
The sulfuric acid is present, as a catalyst, to protonate the nitric acid to form the nitronium ion. The power of guncotton made it suitable for blasting. As a projectile driver, it has around six times the gas generation of an equal volume of black powder and produces less smoke and less heating. Guncotton, dissolved at approximately 25% in acetone, forms a lacquer used in preliminary stages of wood finishing to develop a hard finish with a deep luster.
Nitrocellulose is made using either concentrated sulfuric/nitric acid or sulfuric acid/potassium nitrate. In general, cotton is used as the cellulose. The cellulose is added to the acid mix to nitrate. After the cellulose has finished nitrating, it is washed and dried. Nitrocellulose is stored wet so it cannot be accidentally lit or explode.

Nitrocellulose[19] had many properties that made it an important material apart from its use as a propellant. Since it forms a plastic material when dissolved in organic solvents like ether-alcohol or acetone, it can be made into many different forms that maintain their shape when the solvents evaporate. It can also be hot-formed and will retain its shape when cooled.
The manufacturers of military explosives experienced several instances of extremely high production during the late 19th and early 20th centuries caused by large-scale wars. When peace was reached, there was an enormous excess of production capacity and raw materials with which nitrocellulose could be made. In order to utilize this glut of resources, gunpowder manufacturers began to develop civilian uses for this material.
Since the average consumer has limited need for nitrocellulose gunpowder, other types of uses for this material had to be found. Because it forms a plastic material, it could be developed into other types of products that had broader consumer applications. Gunpowder manufacturers such as E. I. du Pont de Nemours and Company developed the first commercially available plastics for these reasons.
Collodio In all reality, the use of excess gunpowder manufacturing capacity for the production of consumer products was the beginning of the commercial plastics industry. One of the primary compounds that was developed into plastics was collodion and it is simply guncotton with a lower nitrate constituent, less than 12%. This material is also known by the trade name Pyroxylin and it was developed into many different consumer products such as artificial leather, plastic and lacquers.
Celluloid By mixing solid nitrocellulose with camphor, John Wesley Hyatt of Albany, New York developed Celluloid, the first commercially successful plastic. The solid material could be heated until it softened and then molded into various shapes. Hyatt formed the Celluloid Manufacturing Company to manufacture and market these products. The earliest uses of this material were mostly as substitutes for natural materials such as tortoiseshell, horn and ivory. Ivory became very scarce at about this time in part because billiards became very popular. Since billiard balls were heretofore made of ivory, a great amount of ivory was needed to make them. Ivory comes from elephant tusks and therefore the supply is limited.
In keeping with the nitrocellulose origin of these earliest plastics, they tended to be highly flammable. Celluloid and Pyroxylin plastics were only slightly less flammable than gunpowder. In fact, on some occasions items made from Celluloid could explode. This was particularly bothersome with billiard balls where the force of impact would sometimes cause the balls to detonate. While this no doubt occasionally made billiards more interesting, it also had undesirable side effects such as personal injury as well as property destruction. Therefore, the explosive characteristics of Celluloid were generally regarded as negative.
Pyroxylin-type plastics began to be replaced by less flammable plastics in the 1920s and 1930s. Nevertheless they did not disappear. Better chemical manufacturing techniques reduced the incidence of detonation in later years. Celluloid plastics are still used in a few applications such as Ping-Pong balls.