This is accomplished by subjecting the base and a solvent to agitation in a non-solvent medium such as water so as to produce globules that are individually consolidated in order to form grains which are spherical Carlucci and Jacobson Carlucci DE, Jacobson SS Ballistics: theory and design of guns and ammunition.
A volatile solvent may also be used to produce globules, being before vaporized by heating Olsen et al. Suitable solvents include ethyl acetate, isopropyl acetate, methyl isobutyl ketone, as well as other organic liquids which are solvents for nitrocellulose not completely miscible with water Coffee Coffee RE; inventor; Jan Particulate nitrocellulose coated with sorbitan trioleate.
The treatment with the solvent is preferably carried out to an extent sufficient to convert all of the nitrocellulose present in a lacquer Olsen Olsen F, inventor; Aug The desired amount of solvent may be added to the slurry of nitrocellulose dust in the form of a spray and, in this manner, small globules of the solvent may be readily distributed throughout the mixture.
During agitation and heating, the surfaces of the particles of nitrocellulose dust become softened due to the gelatinizing action of the solvent and tend to coalesce, forming clusters comprising a number of dust particles.
This action may be explained since all liquid or plastic two-phase systems tend to a condition of minimum surface energy which can be accomplished by coalescence Olsen et al. The production of globules or the production of the quasi-emulsion may be secured in various ways. The protective colloid performs the function of effecting a quasiemulsion between the base and solvent and the non-solvent medium, with the base and solvent as the internal phase.
The base is agitated with a solvent distributed in the non-solvent vehicle so as to form an emulsion with the medium as the internal phase; upon the addition of the protective colloid the emulsion is broken and under agitation inverted with the medium as the external phase.
The neutralizer is added to remove the highacidity centers. A suitable neutralizer is calcium carbonate in the form of purified prepared chalk Olsen et al. The globules, which are distributed throughout the medium, are then subjected to treatment to extract the solvent, through distillation of the solvent secured by heating the medium to near the vaporizing point of the solvent. The distillation is so carried out as to effect a gradual vaporization of the solvent from the several globules; the process is preferably carried out by effecting vaporization at a rate decreasing from the beginning to the end of the vaporization period and at a rate less than the rate of diffusion of the solvent from the interiors to the exteriors of the globules.
Such a distillation secures a solid grain as distinguished from one which is hollow and porous Olsen et al. After formation of the globules in the medium or vehicle, and after distillation of the solvent from the several globules to form grains, the medium is permitted to cool to a temperature sufficiently low to permit any modifying agent or stabilizer dissolved in the normally non-solvent medium to separate out at the lower temperature.
In the case of the modifying agent, such as deterrent, it will become deposited on the grains so as to provide a surface treatment in the form of a coating or impregnation Olsen et al.
Figure 1 represents a manufacture process of spherical grains of smokeless powders. Figure 1 Spherical powder manufacturing process. The finishing operations are similar to the ones that are usually carried out during the manufacture of a single-base smokeless powder. After cooling of the medium, and when the grains have become consolidated or hardened, they may be subjected to a screening operation, in which the oversizes can be sent back for reworking and the screened grains can be subjected to a wringing operation and thereafter to a drying operation.
The grains may be surface treated prior to drying with a suitable modifying agent, such as a deterrent or an accelerator. The coating may comprise nitroglycerin which acts as an accelerator; in that it allows the powder to be more readily ignitable and also acts as a waterproofing agent, rendering the powder non-hygroscopic.
A suitable deterrent such as dibutylphthalate may be used along with the nitroglycerin or other accelerator and waterproofing agent. The grains may be then dried and glazed in the usual manner and thereafter blended if desired Olsen et al. The size of the grains is a function of the extent and the violence of the agitation as well as the amount of protective colloid and the viscosity of the dissolved base Olsen et al.
The grain size decreases with the increase of rotor speed, the increase of percentage of the colloid and the viscosity of the nitrocellulose. Furthermore the amount of solvent employed affects not only the size, shape and surface of the resultant grains, but also the gravimetric density thereof Schaefer Schaefer HF, inventor; May Small amounts of solvent give a small rough cluster of particles as the grains while larger amounts of solvent give more spherical smoother grains.
The rate at which the temperature is raised during evaporation of the solvent affects both the granulation and density of the resultant powder Schaefer Schaefer HF, inventor; May The process for the manufacture of spherical powder, which Olsen and his co-workers have devised, combines nicely with Olsen's process for the quick stabilization of nitrocellulose to form a sequence of operations by which a finished powder may be produced more rapidly and more safely than by the usual process.
It supplies a convenient means of making up a powder which contains nonvolatile solvents throughout the mass of the grains or deterrent or accelerant coatings upon their surface Urbanski Urbanski T Chemistry and technology of explosives.
Warszawa: Polish Scientific Publishers. Although the spherical powder starts as pure nitrocellulose, the finished product is a double-base propellant, since nitroglycerin is added after shaping and its content is created by surface impregnation. Table 1 provides a comparison between spherical powders and other common double-base smokeless powders with respect to manufacture process, characteristics and uses.
It aims to briefly compare spherical powders against other double-base propellants. This is important since their production is more complex hence expensive than that of extruded propellants.
Due to this, they are used mainly when the ammuntion does so requires. Another important comparison aspect between propellants is the effectiveness and burning characteristics.
This comparison is carried out using Fig. Progressive burning occurs when the thrust produced increases with time and with distance traveled, inside the barrel Kosanke Kosanke K Terminology of model rocketry; [accessed Nov 15]. During a regressive burning, the surface area decreases with time, and so does the thrust. The neutral burning happens when the burning area is approximately constant, which results in a constant thrust over the burning period.
The pressure peak is higher and is reached first in a regressive burning rate because, as the burning area decreases, the gas production lowers, so the maximum pressure occurs in the very beginning of the barrel. On the other side, if a progressive burning propellant is used, the peak pressure is limited to a value that may be tolerated by the gun Moss et al.
London: Pergamon Press. It is also important to address the effect of adding high explosives in the composition on the propellant performance Zhu et al. Figure 2 Pressure-time curves for different burning rates. In Fig. The curves shown in Fig. The spherical powder can be used in small ammunitions to provide a greater muzzle velocity, which will result in a bigger kinetic energy being transferred to the target. A typical peak pressure for a 5. The great advantage of the spherical powder manufacture process is the possibility of using deteriorated and unstable nitrocellulose.
Aged powders that would be destroyed can be reused, which results in a lower production cost. Also, the nitrocellulose stabilization process, that requires a big quantity of water and energy, is not necessary since the process of making the propellant spherical already stabilizes the nitrocellulose.
Hence the process to make the powder spherical substitutes the stabilization process. It did find wide use with artillery. However, within a short time there were a number of massive explosions and fatalities in guncotton factories due to lack of appreciation of its sensitivity and the means of stabilization.
Guncotton then went out of use for some twenty years or more until it could be tamed; it was not until the s that it became a viable propellant. In Paul Vieille invented a smokeless gunpowder called Poudre B , made from gelatinized guncotton mixed with ether and alcohol.
It was passed through rollers to form thin sheets, which were cut into flakes of the desired size. The resulting propellant , today known as pyrocellulose , contains somewhat less nitrogen than guncotton and is less volatile. A particularly good feature of the propellant is that it will not burn unless it is compressed, making it very safe to handle under normal conditions.
Vieille's powder revolutionized the effectiveness of small guns, for several reasons. First, it gave off almost no smoke. After a few shots, a soldier with black powder ammunition would have his view obscured by a huge pall of smoke unless there was a strong wind. Conversely, a sniper or other hidden shooter would not be given away by a cloud of smoke over the firing position.
Further, it was three times more powerful than black powder, which gave more power from less powder. The higher muzzle velocity meant a flatter trajectory and therefore more accurate long range fire, out to perhaps metres in the first smokeless powder rifles. Since less powder was needed to propel a bullet, the cartridge could be made smaller and lighter. This allowed troops to carry more ammunition for the same weight. Also, it would burn even when wet. Black powder ammunition had to be kept dry and was almost always stored and transported in watertight cartridges.
Vielle's powder was used in the Lebel rifle that was immediately introduced by the French Army to exploit its huge benefits over black powder. Other European countries swiftly followed and started using their own versions of Poudre B, the first being Germany and Austria which introduced new weapons in Meanwhile, in Great Britain, in , Alfred Nobel developed a smokeless gunpowder called Ballistite.
A modified form of this was devised by Sir Frederick Abel and James Dewar which eventually became known as Cordite , leading to a lengthy court battle between Nobel and the other two inventors over alleged British patent infringement. These newer propellants were more stable and thus safer to handle than Poudre B, and also more powerful. Today, propellants based on nitrocellulose alone are known as single-base , whereas cordite-like mixtures are known as double-base.
A triple-base flashless cordite was also developed, primarily for large naval guns, but also used in battle tank ammunition. Smokeless powder allowed the development of modern semi- and fully automatic firearms. Burnt blackpowder leaves a thick, heavy fouling which is both hygroscopic and corrosive. Smokeless powder fouling exhibits none of these properties. This makes an autoloading firearm with many moving parts feasible which would jam or seize under heavy blackpowder fouling.
Single and double-base smokeless powders now make up the vast majority of propellants used in firearms. They are so common that most modern references to "gunpowder" refer to a smokeless powder, particularly when referring to small arms ammunition. Smokeless powder is the name given to a number of propellant materials, widely used in firearms and artillery, which replaced black powder. However, despite its name, smokeless powder is rarely a powder, but rather it appears as pellets or extruded granules.
There are lots of categories of smokeless powders, which depend on their properties, such as composition, speed of combustion, etc. Most if not all smokeless powders contain nitrocellulose NC , and they are split into three main groups:.
Smokeless powder is a silvery-gray or dull gray solid, insoluble in all solvents though nitroglycerin and nitroguanidine will dissolve in organic solvents. It is typically odorless, with a density between 0. In Europe, occasionally one might accidentally dug up WWII ammo, which, if intact, still has usable smokeless powder, though of a lower quality than modern powders.
However, due to legal issues surrounding UXOs and common sense, it's best to avoid making a habit out of this practice.
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