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Nitrocellulose
Nitrocellulose
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Nitrocellulose[1]
Cosmetic pads made of nitrocellulose
Names
Other names
Cellulose nitrate; Flash paper; Flash cotton; Flash string; Gun cotton; Collodion; Pyroxylin
Identifiers
ChemSpider
  • none
UNII
Properties
(C
6H
9(NO
2)O
5)
n (mononitrocellulose)

(C
6H
8(NO
2)
2O
5)
n (dinitrocellulose)
(C
6H
7(NO
2)
3O
5)
n (trinitrocellulose, pictured in structures above)

Appearance Yellowish white cotton-like filaments
Melting point 160 to 170 °C (320 to 338 °F; 433 to 443 K) (ignites)
Hazards
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazards (white): no code
2
3
3
Flash point 4.4 °C (39.9 °F; 277.5 K)
Lethal dose or concentration (LD, LC):
10 mg/kg (mouse, IV)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)

Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed by nitrating cellulose through exposure to a mixture of nitric acid and sulfuric acid. One of its first major uses was as guncotton, a replacement for gunpowder as propellant in firearms. It was also used to replace gunpowder as a low-order explosive in mining and other applications. In the form of collodion, it was also a critical component in an early photographic emulsion, the use of which revolutionized photography in the 1860s. In the 20th century, it was adapted to automobile lacquer and adhesives.

Production

[edit]

The process uses a mixture of nitric acid and sulfuric acid to convert cellulose into nitrocellulose.[2] The quality of the cellulose is important. Hemicellulose, lignin, pentosans, and mineral salts give inferior nitrocelluloses. In organic chemistry, nitrocellulose is a nitrate ester, not a nitro compound. The glucose repeat unit (anhydroglucose) within the cellulose chain has three OH groups, each of which can form a nitrate ester. Thus, nitrocellulose can denote mononitrocellulose, dinitrocellulose, and trinitrocellulose, or a mixture thereof. With fewer OH groups than the parent cellulose, nitrocelluloses do not aggregate by hydrogen bonding. The overarching consequence is that the nitrocellulose is soluble in organic solvents such as acetone and esters; e.g., ethyl acetate, methyl acetate, ethyl carbonate.[3] Most lacquers are prepared from the dinitrate, whereas explosives are mainly the trinitrate.[4][5]

The chemical equation for the formation of the trinitrate is
     3 HNO3 + C6H7(OH)3O2 H2SO4 → C6H7(ONO2)3O2 + 3 H2O.

The yields are about 85%, with losses attributed to complete oxidation of the cellulose to oxalic acid.

Use

[edit]

The principal uses of cellulose nitrate is for the production of lacquers and coatings, explosives, and celluloid.[6]

In terms of lacquers and coatings, nitrocellulose dissolves readily in organic solvents, which upon evaporation leave a colorless, transparent, flexible film.[4] Nitrocellulose lacquers have been used as a finish on furniture and musical instruments.[7]

Guncotton, dissolved at about 25% in acetone, forms a lacquer used in preliminary stages of wood finishing to develop a hard finish with a deep lustre.[8] It is normally the first coat applied, then it is sanded and followed by other coatings that bond to it.

Nail polish contains nitrocellulose, as it is inexpensive, dries quickly to a hard film, and does not damage skin.[9]

The explosive applications are diverse and nitrate content is typically higher for propellant applications than for coatings.[6] For space flight, nitrocellulose was used by Copenhagen Suborbitals on several missions as a means of jettisoning components of the rocket/space capsule and deploying recovery systems. However, after several missions and flights, it proved not to have the desired explosive properties in a near vacuum environment.[10] In 2014, the Philae comet lander failed to deploy its harpoons because its 0.3 grams of nitrocellulose propulsion charges failed to fire during the landing.[11]

Other uses

[edit]

Collodion, a solution of nitrocellulose, is used today in topical skin applications, such as liquid skin and in the application of salicylic acid, the active ingredient in Compound W wart remover.[12][13][citation needed]

Laboratory uses

[edit]

Hobbies

[edit]
  • In 1846, nitrated cellulose was found to be soluble in ether and alcohol. The solution was named collodion and was soon used as a dressing for wounds.[17][18]
  • In 1851, Frederick Scott Archer invented the wet collodion process as a replacement for albumen in early photographic emulsions, binding light-sensitive silver halides to a glass plate.[19]
  • Magicians' flash paper are sheets of paper consisting of pure nitrocellulose, which burn almost instantly with a bright flash, leaving no ash or smoke.
  • As a medium for cryptographic one-time pads, they make the disposal of the pad complete, secure, and efficient.
  • Nitrocellulose lacquer is spin-coated onto aluminium or glass discs, then a groove is cut with a lathe, to make one-off phonograph records, used as masters for pressing or for play in dance clubs. They are referred to as acetate discs.
  • Depending on the manufacturing process, nitrocellulose is esterified to varying degrees. Table tennis balls, guitar picks, and some photographic films have fairly low esterification levels and burn comparatively slowly with some charred residue.
Table tennis ball, prepared from nitrocellulose (Celluloid)

Historical uses

[edit]

Early work on nitration of cellulose

[edit]
Pure nitrocellulose
Workman operating a guncotton press behind a protective rope screen, 1909
Deflagration test of nitrocellulose in slow motion

In 1832 Henri Braconnot discovered that nitric acid, when combined with starch or wood fibers, would produce a lightweight combustible explosive material, which he named xyloïdine.[20] A few years later in 1838, another French chemist, Théophile-Jules Pelouze (teacher of Ascanio Sobrero and Alfred Nobel), treated paper and cardboard in the same way.[21] Jean-Baptiste Dumas obtained a similar material, which he called nitramidine.[22]

Guncotton

[edit]

Around 1846 Christian Friedrich Schönbein, a German-Swiss chemist, discovered a more practical formulation.[23] As he was working in the kitchen of his home in Basel, he spilled a mixture of nitric acid (HNO3) and sulfuric acid (H2SO4) on the kitchen table. He reached for the nearest cloth, a cotton apron, and wiped it up. He hung the apron on the stove door to dry, and as soon as it was dry, a flash occurred as the apron ignited. His preparation method was the first to be widely used. The method was to immerse one part of fine cotton in 15 parts of an equal blend of sulfuric acid and nitric acid. After two minutes, the cotton was removed and washed in cold water to set the esterification level and to remove all acid residue. The cotton was then slowly dried at a temperature below 40 °C (104 °F). Schönbein collaborated with the Frankfurt professor Rudolf Christian Böttger, who had discovered the process independently in the same year.

By coincidence, a third chemist, the Brunswick professor F. J. Otto had also produced guncotton in 1846 and was the first to publish the process, much to the disappointment of Schönbein and Böttger.[24][full citation needed]

The patent rights for the manufacture of guncotton were obtained by John Hall & Son in 1846, and industrial manufacture of the explosive began at a purpose-built factory at Marsh Works in Faversham, Kent, a year later. The manufacturing process was not properly understood and few safety measures were put in place. A serious explosion in July that killed almost two dozen workers resulted in the immediate closure of the plant. Guncotton manufacture ceased for over 15 years until a safer procedure could be developed.[25]

The British chemist Frederick Augustus Abel developed the first safe process for guncotton manufacture, which he patented in 1865. The washing and drying times of the nitrocellulose were both extended to 48 hours and repeated eight times over. The acid mixture was changed to two parts sulfuric acid to one part nitric. Nitration can be controlled by adjusting acid concentrations and reaction temperature. Nitrocellulose is soluble in a mixture of ethanol and ether until nitrogen concentration exceeds 12%. Soluble nitrocellulose, or a solution thereof, is sometimes called collodion.[26]

Guncotton containing more than 13% nitrogen (sometimes called insoluble nitrocellulose) was prepared by prolonged exposure to hot, concentrated acids[26] for limited use as a blasting explosive or for warheads of underwater weapons such as naval mines and torpedoes.[27] Safe and sustained production of guncotton began at the Waltham Abbey Royal Gunpowder Mills in the 1860s, and the material rapidly became the dominant explosive, becoming the standard for military warheads, although it remained too potent to be used as a propellant. More-stable and slower-burning collodion mixtures were eventually prepared using less concentrated acids at lower temperatures for smokeless powder in firearms. The first practical smokeless powder made from nitrocellulose, for firearms and artillery ammunition, was invented by French chemist Paul Vieille in 1884.

Jules Verne viewed the development of guncotton with optimism. He referred to the substance several times in his novels. His adventurers carried firearms employing this substance. In his From the Earth to the Moon, guncotton was used to launch a projectile into space.

Because of their fluffy and nearly white appearance, nitrocellulose products are often referred to as cottons, e.g. lacquer cotton, celluloid cotton, and gun cotton.[4]

Guncotton was originally made from cotton (as the source of cellulose) but contemporary methods use highly processed cellulose from wood pulp. While guncotton is dangerous to store, the hazards it presents can be minimized by storing it dampened with various liquids, such as alcohol. For this reason, accounts of guncotton usage dating from the early 20th century refer to "wet guncotton."

Jam tin grenades were made in World War I using gun cotton

The power of guncotton made it suitable for blasting. As a projectile driver, it had around six times the gas generation of an equal volume of black powder and produced less smoke and less heating.

Artillery shells filled with gun cotton were widely used during the American Civil War[contradictory], and its use was one of the reasons the conflict was seen as the "first modern war."[28] Fired from breech-loading artillery, such high explosive shells could cause greater damage than previous solid round shot.

During the first World War, British authorities were slow to introduce new grenades, with soldiers at the front improvising by filling ration tin cans with gun cotton, scrap and a basic fuse.[29]

Further research indicated the importance of washing the acidified cotton. Unwashed nitrocellulose (sometimes called pyrocellulose) may spontaneously ignite and explode at room temperature, as the evaporation of water results in the concentration of unreacted acid.[27]

Film

[edit]
See also: Film base § Nitrate
Nitrocellulose film on a light box, showing deterioration, from Library and Archives Canada collection

In 1855, the first human-made plastic, nitrocellulose (branded Parkesine, patented in 1862), was created by Alexander Parkes from cellulose treated with nitric acid and a solvent. In 1868, American inventor John Wesley Hyatt developed a plastic material he named Celluloid, improving on Parkes' invention by plasticizing the nitrocellulose with camphor so that it could be processed into a photographic film. This was used commercially as "celluloid", a highly flammable plastic that until the mid-20th century formed the basis for lacquers and photographic film.[8]

On May 2, 1887, Hannibal Goodwin filed a patent for "a photographic pellicle and process of producing same ... especially in connection with roller cameras", but the patent was not granted until September 13, 1898.[30] In the meantime, George Eastman had already started production of roll-film using his own process.

Nitrocellulose was used as the first flexible film base, beginning with Eastman Kodak products in August 1889. Camphor is used as a plasticizer for nitrocellulose film, often called nitrate film. Goodwin's patent was sold to Ansco, which successfully sued Eastman Kodak for infringement of the patent and was awarded $5,000,000 in 1914 to Goodwin Film.[31]

Nitrate film fires

[edit]
A reel of nitrate film that has caught fire inside a projector after breaking inside the mechanism and igniting from the heat of the lamp

Disastrous fires related to celluloid or "nitrate film" became regular occurrences in the motion picture industry throughout the silent era and for many years after the arrival of sound film.[32] Projector fires and spontaneous combustion of nitrate footage stored in studio vaults and in other structures were often blamed during the early to mid 20th century for destroying or heavily damaging cinemas, inflicting many serious injuries and deaths, and for reducing to ashes the master negatives and original prints of tens of thousands of screen titles,[33] turning many of them into lost films. Even when nitrate stock did not start the blaze, flames from other sources spread to large nearby film collections, producing intense and highly destructive fires.

In 1914—the same year that Goodwin Film was awarded $5,000,000 from Kodak for patent infringement—nitrate film fires incinerated a significant portion of the United States' early cinematic history. In that year alone, five very destructive fires occurred at four major studios and a film-processing plant. Millions of feet of film burned on March 19 at the Eclair Moving Picture Company in Fort Lee, New Jersey.[34] Later that same month, many more reels and film cans of negatives and prints also burned at Edison Studios in New York City, in the Bronx. On May 13, a fire at Universal Pictures' Colonial Hall "film factory" in Manhattan consumed another extensive collection.[35][36] Yet again, on June 13 in Philadelphia, a fire and a series of explosions ignited inside the 186-square-meter (2,000-square-foot) film vault of the Lubin Manufacturing Company and quickly wiped out virtually all of that studio's pre-1914 catalogue.[37] Then a second fire hit the Edison Company at another location on December 9, at its film-processing complex in West Orange, New Jersey. That catastrophic fire started inside a film-inspection building and caused over $7,000,000 in property damages ($220,000,000 today).[38] Even after film technology changed, archives of older films remained vulnerable; the 1965 MGM vault fire burned many films that were decades old.

Lubin film vault custodian Stanley Lowry (foreground) surveys the rubble after fire and explosions, June 1914

The use of volatile nitrocellulose film for motion pictures led many cinemas to fireproof their projection rooms with wall coverings made of asbestos. Those additions intended to prevent or at least delay the migration of flames beyond the projection areas. A training film for projectionists included footage of a controlled ignition of a reel of nitrate film, which continued to burn even when fully submerged in water.[39] Once burning, it is extremely difficult to extinguish. Unlike most other flammable materials, nitrocellulose does not need a source of air to continue burning, since it contains sufficient oxygen within its molecular structure to sustain a flame. For this reason, immersing burning film in water may not extinguish it, and could actually increase the amount of smoke produced.[40] Owing to public safety precautions, the United Kingdom's Health and Safety Executive to this day forbids transportation of nitrate film by post or public transit, or disposal with household refuse.[41]

Cinema fires caused by the ignition of nitrocellulose film stock commonly occurred as well. In Ireland in 1926, it was blamed for the Dromcolliher cinema tragedy in County Limerick in which 48 people died. Then in 1929 at the Glen Cinema in Paisley, Scotland, a film-related fire killed 69 children. Today, nitrate film projection is rare and normally highly regulated and requires extensive precautions, including extra health-and-safety training for projectionists. A special projector certified to run nitrate films has many modifications, among them the chambering of the feed and takeup reels in thick metal covers with small slits to allow the film to run through them. The projector is additionally modified to accommodate several fire extinguishers with nozzles aimed at the film gate. The extinguishers automatically trigger if a piece of film near the gate starts to burn. While this triggering would likely damage or destroy a significant portion of the projector's components, it would contain a fire and prevent far greater damage. Projection rooms may also be required to have automatic metal covers for the projection windows, preventing the spread of fire to the auditorium. Today, the Dryden Theatre at the George Eastman Museum is one of a few theaters in the world that is capable of safely projecting nitrate films and regularly screens them to the public.[42][43] The BFI Southbank in London is the only cinema in the United Kingdom licensed to show Nitrate Film.[44]

The use of nitrate film and its fiery potential were certainly not issues limited to the realm of motion pictures or to commercial still photography. The film was also used for many years in medicine, where its hazardous nature was most acute, especially in its application to X-ray photography.[8] In 1929, several tons of stored X-ray film were ignited by steam from a broken heating pipe at the Cleveland Clinic in Ohio. That tragedy claimed 123 lives during the fire and additional fatalities several days later, when hospitalized victims died due to inhaling excessive amounts of smoke from the burning film, which was laced with toxic gases such as sulfur dioxide and hydrogen cyanide.[45][46] Related fires in other medical facilities prompted the growing disuse of nitrocellulose stock for X-rays by 1933, nearly two decades before its use was discontinued for motion-picture films in favour of cellulose acetate film, more commonly known as "safety film".

Decayed nitrate film, EYE Film Institute Netherlands

Nitrocellulose decomposition and new "safety" stocks

[edit]

Nitrocellulose was found to gradually decompose, releasing nitric acid and further catalyzing the decomposition (eventually into a flammable powder). Decades later, storage at low temperatures was discovered as a means of delaying these reactions indefinitely. Many films produced during the early 20th century were lost through this accelerating, self-catalyzed disintegration or through studio warehouse fires, and many others were deliberately destroyed specifically to avoid the fire risk. Salvaging old films is a major problem for film archivists (see film preservation).

Nitrocellulose film base manufactured by Kodak can be identified by the presence of the word "nitrate" in dark letters along one edge; the word only in clear letters on a dark background indicates derivation from a nitrate base original negative or projection print, but the film in hand itself may be a later print or copy negative, made on safety film. Acetate film manufactured during the era when nitrate films were still in use was marked "Safety" or "Safety Film" along one edge in dark letters. 8, 9.5, and 16 mm film stocks, intended for amateur and other nontheatrical use, were never manufactured with a nitrate base in the west, but rumors exist of 16 mm nitrate film having been produced in the former Soviet Union and China.[47]

Nitrate dominated the market for professional-use 35 mm motion picture film from the industry's origins to the early 1950s. While cellulose acetate-based safety film, notably cellulose diacetate and cellulose acetate propionate, was produced in the gauge for small-scale use in niche applications (such as printing advertisements and other short films to enable them to be sent through the mails without the need for fire safety precautions), the early generations of safety film base had two major disadvantages relative to nitrate: it was much more expensive to manufacture, and considerably less durable in repeated projection. The cost of the safety precautions associated with the use of nitrate was significantly lower than the cost of using any of the safety bases available before 1948. These drawbacks were eventually overcome with the launch of cellulose triacetate base film by Eastman Kodak in 1948.[48] Cellulose triacetate superseded nitrate as the film industry's mainstay base very quickly. While Kodak had discontinued some nitrate film stocks earlier, it stopped producing various nitrate roll films in 1950 and ceased production of nitrate 35 mm motion picture film in 1951.[49]

The crucial advantage cellulose triacetate had over nitrate was that it was no more of a fire risk than paper (the stock is often referred to as "non-flam": this is true—but it is combustible, just not in as volatile or as dangerous a way as nitrate), while it almost matched the cost and durability of nitrate. It remained in almost exclusive use in all film gauges until the 1980s, when polyester/PET film began to supersede it for intermediate and release printing.[50]

Polyester is much more resistant to polymer degradation than either nitrate or triacetate. Although triacetate does not decompose in as dangerous a way as nitrate does, it is still subject to a process known as deacetylation, often nicknamed "vinegar syndrome" (due to the acetic acid smell of decomposing film) by archivists, which causes the film to shrink, deform, become brittle and eventually unusable.[51] PET, like cellulose mononitrate, is less prone to stretching than other available plastics.[50] By the late 1990s, polyester had almost entirely superseded triacetate for the production of intermediate elements and release prints.

Triacetate remains in use for most camera negative stocks because it can be "invisibly" spliced using solvents during negative assembly, while polyester film is usually spliced using adhesive tape patches, which leave visible marks in the frame area. However, ultrasonic splicing in the frame line area can be invisible. Also, polyester film is so strong, it will not break under tension and may cause serious damage to expensive camera or projector mechanisms in the event of a film jam, whereas triacetate film breaks easily, reducing the risk of damage. Many were opposed to the use of polyester for release prints for this reason, and because ultrasonic splicers are very expensive, beyond the budgets of many smaller theaters. In practice, though, this has not proved to be as much of a problem as was feared. Rather, with the increased use of automated long-play systems in cinemas, the greater strength of polyester has been a significant advantage in lessening the risk of a film performance being interrupted by a film break.[citation needed]

Despite its self-oxidizing hazards, nitrate is still regarded highly as the stock is more transparent than replacement stocks, and older films used denser silver in the emulsion. The combination results in a notably more luminous image with a high contrast ratio.[52]

Fabric

[edit]

The solubility of nitrocellulose was the basis for the first "artificial silk" by Georges Audemars in 1855, which he called "Rayon".[citation needed]. However, Hilaire de Chardonnet was the first to patent a nitrocellulose fiber marketed as "artificial silk" at the Paris Exhibition of 1889.[53] Commercial production started in 1891, but the result was flammable and more expensive than cellulose acetate or cuprammonium rayon. Because of this predicament, production ceased early in the 1900s. Nitrocellulose was briefly known as "mother-in-law silk".[54]

Frank Hastings Griffin invented the double-godet, a special stretch-spinning process that changed artificial silk to rayon, rendering it usable in many industrial products such as tire cords and clothing.[55] Nathan Rosenstein invented the "spunize process" by which he turned rayon from a hard fiber to a fabric. This allowed rayon to become a popular raw material in textiles.

Coatings

[edit]

Nitrocellulose lacquer manufactured by (among others) DuPont, was the primary material for painting automobiles for many years. Durability of finish, complexities of "multiple stage" modern finishes, and other factors including environmental regulation led manufacturers to choose newer technologies. It remained the favorite of hobbyists for both historical reasons and for the ease with which a professional finish can be obtained. Most automobile "touch up" paints are still made from lacquer because of its fast drying, easy application, and superior adhesion properties – regardless of the material used for the original finish. Guitars sometimes shared color codes with current automobiles. It fell out of favor for mass production use for a number of reasons including environmental regulation and the cost of application vs. polyurethane finishes. However, Gibson still use nitrocellulose lacquers on all of their guitars, as well as Fender when reproducing historically accurate guitars. The nitrocellulose lacquer yellows and cracks over time, and custom shops will reproduce this aging to make instruments appear vintage. Guitars made by smaller shops (luthiers) also often use "nitro" as it has an almost mythical status among guitarists.

Hazards

[edit]
'United States Inter-Agency Committee for Nitrate Film Vault Tests' – film transfer from 1948 about testing storage and flame suppression methods of nitrate film stock; runtime 00:08:41

Because of its explosive nature, not all applications of nitrocellulose were successful. In 1869, with elephants having been poached to near extinction, the billiards industry offered a US$10,000 prize to whoever came up with the best replacement for ivory billiard balls. John Wesley Hyatt created the winning replacement, which he created with a new material he invented, called camphored nitrocellulose—the first thermoplastic, better known as celluloid. The invention enjoyed a brief popularity, but the Hyatt balls were extremely flammable, and sometimes portions of the outer shell would explode upon impact. An owner of a billiard saloon in Colorado wrote to Hyatt about the explosive tendencies, saying that he did not mind very much personally but for the fact that every man in his saloon immediately pulled a gun at the sound.[56][57] The process used by Hyatt to manufacture the billiard balls, patented in 1881,[58] involved placing the mass of nitrocellulose in a rubber bag, which was then placed in a cylinder of liquid and heated. Pressure was applied to the liquid in the cylinder, which resulted in a uniform compression on the nitrocellulose mass, compressing it into a uniform sphere as the heat vaporized the solvents. The ball was then cooled and turned to make a uniform sphere. In light of the explosive results, this process was called the "Hyatt gun method".[59]

An overheated container of dry nitrocellulose is believed to be the initial cause of the 2015 Tianjin explosions.[60]

See also

[edit]

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Nitrocellulose

View on Grokipedia
from Grokipedia
Nitrocellulose, also known as cellulose nitrate, is a highly flammable and derivative of in which some of the hydroxyl groups are replaced by nitro groups, resulting in a with the general formula [C₆H₇O₂(ONO₂)₃]ₙ for the fully nitrated form. This chemical modification imparts unique properties such as rapid and solubility in organic solvents, making it versatile for industrial applications ranging from propellants to coatings. The discovery of nitrocellulose occurred in 1845 when German-Swiss chemist Christian Friedrich Schönbein accidentally nitrated fibers by treating them with a mixture of nitric and sulfuric acids, leading to the creation of "guncotton," an explosive far more powerful than traditional . Schönbein's work built on earlier experiments, such as those by French chemist Henri Braconnot in 1832, who produced explosive materials from and , but nitrocellulose from marked a significant advancement in high explosives. By the late , its potential was harnessed in military contexts, including as a in firearms and , revolutionizing while also posing handling risks due to its sensitivity to friction, heat, and shock. Nitrocellulose is produced industrially through the of purified —typically derived from linters or wood pulp—with a concentrated mixture of nitric and sulfuric acids at controlled temperatures to achieve desired content, usually between 10.7% and 13.5% for commercial grades. The degree of nitration determines its properties: lower levels (around 11-12%) yield plasticized forms suitable for lacquers and films, while higher levels (12.6-13.5%) produce variants like guncotton. Post-nitration, the product is stabilized by washing and boiling to remove residual acids, preventing decomposition, and often plasticized with compounds like for non-explosive uses. Beyond explosives and propellants, nitrocellulose finds widespread application in coatings and finishes, where it serves as a base for quick-drying lacquers used on wood, , and automobiles due to its and gloss properties. In the industry, it is a key ingredient in gravure and flexographic inks for , providing and resistance to oils. Additionally, nitrocellulose is employed in adhesives, cosmetics (such as nail polishes for film-forming ability), and medical diagnostics (e.g., membranes in lateral flow assays), highlighting its role in both traditional and modern technologies. Its flammability necessitates careful handling, with stabilized forms often containing up to 30% or alcohol to mitigate risks. Recent research continues to explore nitrocellulose's potential, including novel synthesis methods like ultrasound-assisted for more efficient production and applications in such as biocompatible films and propellants with reduced environmental impact. These developments underscore its enduring relevance despite historical incidents like factory explosions and fires that prompted safer alternatives in cinema.

Introduction and Chemistry

Definition and Structure

Nitrocellulose, commonly referred to as cellulose nitrate, is a versatile classified as a derivative of the natural . It is produced through the esterification process, where the hydroxyl (-OH) groups on the cellulose chain react with to form nitrate ester linkages (-ONO₂). This modification transforms the relatively stable and hydrophilic cellulose into a material with enhanced reactivity, particularly in terms of flammability and solubility in certain organic solvents. The molecular structure of nitrocellulose is based on the linear backbone of , a composed of repeating β-(1→4)-linked D-glucose units, each contributing the base formula C₆H₁₀O₅. In nitrocellulose, up to three hydroxyl groups per anhydroglucose unit are substituted with groups, leading to a general represented as [C₆H₇O₂(ONO₂)₃₋ₓ(OH)ₓ]ₙ, where n denotes the (typically 200–3,000 units) and x (0 ≤ x ≤ 3) reflects the degree of substitution (DS), which determines the compound's specific properties such as content and stability. For fully nitrated cellulose (DS = 3), the repeating unit is C₆H₇N₃O₁₁, with a molecular weight per unit of approximately 297 g/mol. Structurally, the glucose ring in each unit features hydroxyl groups at the C₂, C₃ (secondary alcohols on the ring), and C₆ (primary alcohol on the CH₂OH side chain) positions, all of which are accessible for . The nitrate groups attach via the oxygen atom of the bond, forming -O-NO₂, as opposed to direct nitro (-NO₂) substitution on carbon, which distinguishes nitrocellulose from true nitro compounds. This configuration can be visualized as the chain with pendant -ONO₂ groups at these key carbons, often depicted in schematic diagrams showing the ring with the β-1,4 glycosidic linkages intact but modified substituents. The primary difference from unmodified lies in the partial or full replacement of -OH groups with -ONO₂, which introduces oxygen-rich functional groups that lower the for and promote rapid oxidation, rendering nitrocellulose highly flammable and capable of self-sustaining . This structural alteration eliminates much of cellulose's hydrogen bonding network, improving in esters and ethers while conferring potential in high-DS forms.

Nitrification Degrees and Variants

Nitrocellulose is classified primarily by its degree of , which is quantified by the percentage of content (%N), reflecting the average number of groups per glucose unit in the chain. Low-nitrated nitrocellulose, with 10.7-11.7% N (corresponding to a degree of substitution of approximately 2.0-2.2), is suitable for applications such as lacquers and coatings due to its enhanced in alcohol-ether mixtures. In contrast, high-nitrated forms, containing 12.5-13.5% N (degree of substitution around 2.4-2.7), exhibit properties and are used in propellants and . These ranges determine key physical behaviors, with nitrogen content directly influencing stability, , and reactivity. Variants of nitrocellulose include cellulose dinitrate and cellulose trinitrate, based on the predominant substitution level. Cellulose dinitrate, averaging two nitrate groups per anhydroglucose unit, typically has about 11.15% N and shows good solubility in polar organic solvents like and acetone. Cellulose trinitrate, with three nitrate groups and a theoretical maximum of 14.14% N, is less common in practice due to processing challenges but demonstrates high energy output in explosive applications; it remains insoluble in yet soluble in ethers and ketones. Solubility generally decreases with increasing nitration degree—low-nitrated variants dissolve readily in alcohols, while high-nitrated ones require more aggressive solvents like —impacting their formulation in industrial uses. The nitrogen content is determined through standardized analytical methods to ensure quality and consistency. The traditional DuPont nitrometer method involves reducing nitrates to and measuring evolved gas volume, providing precise %N values up to 13.8% with high accuracy for commercial samples. Modern alternatives include via Dumas combustion, where the sample is pyrolyzed and nitrogen oxides are reduced to N2 for thermal conductivity detection, offering rapid results (3-4 minutes) and suitability for routine testing. These techniques are essential for verifying the degree of without altering the material's structure. Historically, high-nitrated nitrocellulose (around 12.6% N) was termed pyrocellulose, reflecting its use in early smokeless powders due to improved burn rates compared to fully nitrated guncotton. This naming arose in the late 19th century during advancements in propellant technology, distinguishing it from lower-nitrated forms like pyroxylin used in .

Production Methods

Nitration Process

Nitrocellulose is synthesized through the of , a natural derived primarily from linters or wood pulp, which serves as the key due to its high purity and structural integrity. These cellulose sources are first purified by processes such as and bleaching to remove impurities, then immersed in a nitrating bath consisting of a mixed acid solution of concentrated (HNO₃) and (H₂SO₄), typically in a ratio that facilitates the reaction while minimizing side products. The reaction mechanism involves the catalytic action of sulfuric acid, which protonates nitric acid to generate the electrophilic nitronium ion (NO₂⁺), enabling it to attack the hydroxyl (-OH) groups on the cellulose chain. This electrophilic substitution replaces the hydrogen of the hydroxyl with a nitrate group (-ONO₂), forming the nitrate ester bonds characteristic of nitrocellulose, as represented by the simplified equation: Cellulose-OH+HNO3→Cellulose-ONO2+H2O\text{Cellulose-OH} + \text{HNO}_3 \rightarrow \text{Cellulose-ONO}_2 + \text{H}_2\text{O} The process yields nitrocellulose with varying degrees of substitution depending on reaction conditions, typically ranging from 10.7% to 13.5% content. Key process variables are tightly controlled to achieve the desired degree and product quality. is maintained between 0°C and 30°C to regulate the and prevent excessive degradation or uneven substitution, with lower temperatures favoring higher content. The acid mixture commonly employs a sulfuric-to-nitric ratio of approximately 3:1 by weight, where acts both as a catalyst and dehydrating agent to sustain NO₂⁺ formation. Reaction time typically spans 30 to 60 minutes, allowing sufficient diffusion of the nitrating mixture into the fibers while avoiding over-nitration. Industrial production of nitrocellulose employs both batch and continuous methods. The traditional batch involves immersing pre-treated cellulose in a stirred nitrating bath within a mechanical dipper or , enabling precise control but limiting throughput. In contrast, modern continuous methods, such as nitration, feed cellulose and acids into a dynamic system where materials are continuously mixed and reacted, improving efficiency, reducing waste, and accommodating larger-scale operations. As of 2025, advancements like chipping technology for sheet wood pulp have been developed, using semi-industrial choppers to produce chips (approximately 1.5 cm × 1.5 cm) for nitration, reducing the acid-to-cellulose ratio (from 65:1 to 30:1 in the nitrator), increasing batch capacity up to 2.5–3 times, and lowering production costs while maintaining E-grade quality.

Purification and Quality Control

Following the nitration process, nitrocellulose undergoes purification to remove residual acids and impurities. The crude product is first centrifuged or filtered to separate spent nitrating acids, then subjected to multiple hot water washes to eliminate sulfuric and nitric acid residues. Neutralization follows, typically using a dilute sodium carbonate solution to raise the pH to approximately 6-7, ensuring removal of acidic byproducts while avoiding alkaline degradation. This step is conducted in a beater or mixer, with subsequent water rinses to eliminate alkali traces, yielding a purified, water-wet nitrocellulose slurry. Stabilization is essential to prevent spontaneous decomposition from unstable nitrate groups formed during nitration. The purified nitrocellulose is boiled in water, often repeatedly, to hydrolyze these unstable esters and promote uniform stability. For certain grades, immersion in alcohol or alcohol-water mixtures further stabilizes the material by reducing sensitivity to and impact, while maintaining it in a wet state to inhibit autoignition. These treatments ensure the product can be safely stored and processed without risk of exothermic reactions. Quality control focuses on key metrics to verify suitability for specific applications. Nitrogen content is measured to confirm uniformity, typically targeting 11.8-12.2% for low-viscosity grades used in lacquers and films, as higher levels affect and explosivity. testing, often via viscometry in solution, assesses film-forming properties, with values exceeding 1000 mPa·s indicating high-quality industrial grades. Absence of impurities, such as residues below 0.1%, is confirmed through or conductivity tests to prevent discoloration or instability. Modern quality controls employ advanced analytical techniques for precise characterization. Fourier-transform infrared (FTIR) spectroscopy identifies nitrate groups via characteristic absorption bands around 1650 cm⁻¹ and 1280 cm⁻¹, enabling quantitative assessment of degree and purity. , analyzed by diffraction or , ensures uniformity for applications, where consistent sizes (e.g., 10-50 μm) optimize burn rates and reduce variability. These methods provide non-destructive, rapid verification, supporting compliance with industrial standards.

Physical and Chemical Properties

Solubility and Stability

Nitrocellulose exhibits distinct solubility profiles depending on its degree of nitration, typically expressed as nitrogen content. Across all variants, it is insoluble in water due to its non-polar nitro groups disrupting hydrogen bonding with aqueous solvents. Low-nitration grades, with approximately 11-12% nitrogen content, are soluble in more polar organic solvents such as acetone and ethanol, facilitating their use in lacquers and coatings. In contrast, high-nitration grades (12.5-13.5% nitrogen) show reduced solubility in these solvents but dissolve readily in ether-alcohol mixtures, which is essential for propellant formulations. Nitrocellulose is hygroscopic, readily absorbing moisture from the atmosphere, which can compromise its structural integrity and accelerate degradation over time. To mitigate this, proper storage involves maintaining low environments (below 50% relative humidity) and using desiccants. Long-term stability is further enhanced by incorporating plasticizers such as , particularly in composite materials like , where (typically 30% by weight) reduces brittleness and prevents moisture-induced cracking during extended storage periods of years to decades. Without such stabilization, absorbed can lead to of esters, reducing molecular weight and mechanical performance. In terms of mechanical properties, nitrocellulose forms flexible films and fibers when cast from solution, with lacquer-grade variants exhibiting tensile strengths in the range of 35-70 MPa and elongations of 10-40% under standard conditions (23°C, 50% relative ). These properties arise from its polymeric structure, allowing it to create durable, transparent coatings with good to substrates. However, nitrocellulose demonstrates pH sensitivity, remaining stable in neutral environments but undergoing hydrolytic degradation in acidic or basic conditions; strong acids or bases cleave the nitrate bonds, leading to denitration and loss of material integrity within hours to days of exposure.

Thermal and Explosive Behavior

Nitrocellulose exhibits significant thermal instability, with decomposition initiating at an onset of approximately 150°C and the exothermic phase accelerating around 180°C. This process involves the breakdown of nitrate ester groups, leading to an that releases nitrogen oxides () and other gaseous products, potentially escalating to runaway if not controlled. A simplified representation of the decomposition for the trinitrated form (guncotton) is given by the equation: 2[\ceC6H7O2(ONO2)3]→9\ceCO+3\ceCO2+7\ceH2O+3\ceN22[\ce{C6H7O2(ONO2)3}] \rightarrow 9\ce{CO} + 3\ce{CO2} + 7\ce{H2O} + 3\ce{N2} This reaction highlights the rapid evolution of gases and heat, contributing to the material's propensity for violent response under thermal stress. In explosive applications, nitrocellulose, particularly in its high-nitration variants like guncotton (nitrogen content >12.6%), demonstrates detonation velocities ranging from 6,000 to 8,000 m/s, characterized by a transition from initial deflagration (subsonic burning) to detonation (supersonic shock propagation). This high-velocity detonation is facilitated by the material's ability to sustain a self-propagating reaction wave, making it suitable for propellants but requiring careful confinement to achieve full detonation. Sensitivity to initiation increases with higher nitrogen content, as elevated nitration degrees enhance reactivity to impact and friction, lowering the energy threshold for ignition—typically measured in impact tests where higher-nitrogen samples show reduced drop heights for initiation. To mitigate risks, nitrocellulose is often stabilized by incorporating additives such as or ethyl centralite, which scavenge acidic byproducts and inhibit autocatalytic , thereby raising the and reducing the likelihood of spontaneous ignition during storage or handling. Calorimetric reveals a of around 6.5 MJ/kg for highly nitrated forms, underscoring the substantial release potential that drives its behavior while emphasizing the need for stringent protocols.

Applications

Explosives and Propellants

Nitrocellulose, particularly in its highly nitrated form known as guncotton, has been a foundational material in explosives and propellants since its invention in 1845 by Christian Friedrich Schönbein. Guncotton, with a nitrogen content exceeding 12.9%, exhibits rapid combustion that generates significant gas volumes, making it ideal for energetic applications. This form of nitrocellulose forms the base of smokeless powders, such as cordite developed in 1889, which incorporates nitrocellulose gelatinized with nitroglycerin to enhance energy density and control detonation. In these formulations, nitrocellulose provides the primary energetic component, decomposing exothermically to produce hot gases that propel projectiles with reduced residue compared to black powder. Propellants based on nitrocellulose are classified as single-base or double-base depending on composition and performance characteristics. Single-base propellants rely solely on nitrocellulose, typically stabilized with additives like to prevent degradation, and are used in applications requiring consistent, moderate energy release, such as small arms . Double-base propellants combine nitrocellulose with or other esters, which gelatinize the mixture and increase burning efficiency, often applied in and higher-velocity systems. The burning rate of these propellants, influenced by , pressure, and formulation, generally ranges from 10 to 50 cm/s under operational conditions, allowing tunable thrust profiles for various ballistic needs. In modern applications, nitrocellulose continues to play a vital role in advanced energetic systems. It is incorporated into propellants, where homogeneous or composite formulations leverage its rapid decomposition for reliable , achieving specific impulses of approximately 200-250 seconds depending on additives like aluminum for enhanced . Additionally, nitrocellulose-based compositions serve as gas generators in devices, such as inflators and seatbelt pretensioners, where controlled combustion rapidly produces gas to deploy restraints without toxic byproducts. These uses highlight nitrocellulose's versatility, though its thermal sensitivity—decomposing above 150-180°C—requires careful stabilization to ensure safe handling in matrices.

Coatings and Adhesives

Nitrocellulose serves as a key binder in various coatings and adhesives due to its ability to form tough, flexible films when dissolved in organic solvents. Its solubility in esters such as enables the creation of clear, durable finishes that protect surfaces while enhancing aesthetic appeal. In these applications, lower degrees of —typically with content below 12.6%—are preferred to achieve the necessary thermoplasticity and compatibility with other formulation components. In lacquers and varnishes, nitrocellulose is dissolved in solvents like to produce fast-drying finishes commonly applied to and furniture. These coatings provide a smooth, glossy surface that resists wear and environmental exposure, with touch-dry times ranging from 10 to 15 minutes and sandable dryness achieved in 20 to 30 minutes under standard conditions. The rapid evaporation of solvents contributes to efficient application processes in industries. Low-nitration grades of nitrocellulose are essential in nail polishes and inks, where they impart flexibility, gloss, and moderate to substrates. In nail polishes, nitrocellulose forms a protective film that enhances shine while allowing for easy removal, with its properties ensuring durability without brittleness. For inks, these grades enable high solids loading and quick-setting , supporting vibrant prints on flexible packaging materials. Nitrocellulose-rubber blends are utilized in adhesives for bonding materials like shoes and , offering tack and flexibility under stress. These formulations, often based on polychloroprene or , achieve lap shear strengths of approximately 5 to 10 MPa, making them suitable for demanding joints that require both peel resistance and durability. The primary advantages of nitrocellulose in coatings and adhesives include quick drying, which minimizes production downtime, and high adhesion to diverse substrates, enhanced by blending with resins such as alkyds. Alkyd-modified nitrocellulose formulations improve overall durability, gloss retention, and resistance to chemicals, broadening their utility in industrial settings.

Film and Photographic Materials

Nitrocellulose played a pivotal role in the development of early flexible substrates for imaging technologies, most notably through its use in , a pioneering invented by in 1869. Hyatt discovered that mixing nitrocellulose with as a , along with alcohol, produced a moldable material that could be heated and shaped into durable objects. This composition allowed to serve as an substitute for items like combs and billiard balls, but its transparency and flexibility soon made it ideal for photographic and cinematographic films. By the late , sheets formed the base for early flexible films, enabling the transition from rigid plates to portable media in photography and motion pictures. In the realm of motion pictures, nitrocellulose-based film, often referred to as nitrate stock, became the standard for 35mm film from the early 1900s through the 1950s. This material provided excellent clarity and dimensional stability for projecting images, supporting the rapid growth of the film industry during the silent era and beyond. However, its high flammability prompted regulatory measures, including bans on nitrate film in several countries by the mid-20th century, accelerating the shift to safer alternatives. Nitrocellulose also found application in photographic emulsions, particularly as lacquers in the wet collodion process, which dominated mid-19th-century . In this method, a solution of nitrocellulose dissolved in and alcohol—known as —was poured onto plates to create a thin, . The plate was then sensitized by immersion in , forming light-sensitive crystals embedded within the nitrocellulose layer, which bound the effectively for exposure and development. This technique allowed for detailed negatives on portable supports, bridging early daguerreotypes and later processes. The widespread use of nitrocellulose in film declined sharply starting in the 1920s, as —marketed as "safety film"—was introduced to mitigate flammability risks. By 1937, acetate had largely replaced nitrate in motion picture and photographic stocks, with full industry adoption by 1950. Today, residual applications persist in specialty art films and archival reproductions, where nitrocellulose's unique are valued despite the dominance of modern synthetics.

Medical and Industrial Uses

Nitrocellulose membranes are widely utilized in medical and settings for protein detection through Western blotting techniques, where they serve as a solid support for immobilizing proteins transferred from . These membranes typically feature pore sizes ranging from 0.1 to 0.45 μm, allowing efficient binding of proteins while retaining structural integrity during probing and detection processes. Nitrocellulose membranes also find use in dialysis applications, particularly for laboratory-based purification and buffer exchange in biomedical research, where their semi-permeable structure facilitates the removal of small molecules while retaining larger biomolecules. Industrially, nitrocellulose is blended with plastics such as to create filaments for fused deposition modeling (FDM) , a development prominent since the , enabling rapid prototyping of specialized components like propellants. These composites offer enhanced mechanical properties and printability for manufacturing high-performance materials in and defense sectors. Additionally, nitrocellulose contributes to the production of through composites, often involving vinyl or fabric bases coated with nitrocellulose solutions to mimic the texture and durability of natural for and consumer goods. This application relies on nitrocellulose's film-forming capabilities, historically exemplified in products like Fabrikoid, which combine it with pigments and plasticizers for flexible, embossed surfaces.

Historical Context

Early Discoveries and Guncotton

In 1845, German-Swiss chemist Christian Friedrich Schönbein accidentally discovered nitrocellulose while experimenting with a mixture of concentrated nitric and sulfuric acids in his at the . He spilled the acids on his wife's , used the apron to absorb the spill, and hung it near a hot stove to dry; the material then burst into flames upon heating, prompting Schönbein to systematically nitrate fibers using the acid mixture, producing a highly flammable substance. Schönbein named this product "xyloidin" initially, recognizing its woody texture and explosive potential, though it soon became widely known as guncotton due to its resemblance in use to but with far greater force. Schönbein published his findings in 1846 and secured patents for guncotton production in Britain and the that same year, describing a involving immersion of in the nitrating bath followed by thorough washing and drying. The substance's development accelerated with British government trials in 1847 at the Purfleet powder magazine near , where guncotton was tested in and blasting applications; it exhibited an explosive force approximately four times that of black , propelling projectiles farther with less residue and smoke. Upon detonation, guncotton decomposes rapidly into gaseous products, primarily , , , and , as approximated by the reaction for its tri-nitrated form: 2\ceC6H7O2(NO2)3→3\ceCO2+9\ceCO+3\ceN2+7\ceH2O2 \ce{C6H7O2(NO2)3} \rightarrow 3 \ce{CO2} + 9 \ce{CO} + 3 \ce{N2} + 7 \ce{H2O} This equation highlights the high volume of gases (about 900 liters per kilogram at standard conditions) responsible for its brisant power. Early 19th-century experiments with guncotton were hampered by its chemical instability, stemming from residual sulfuric and nitric acids that promoted slow decomposition and spontaneous ignition. Schönbein's initial production methods yielded inconsistent material prone to degradation, leading to failed military adoptions and catastrophic storage incidents. In July 1847, just months after the British trials, the world's first commercial guncotton factory at Faversham, Kent—operated by Hall & Sons under Schönbein's license—exploded during a thunderstorm, killing 21 workers and destroying the facility due to static sparks igniting unstable batches. Similar disasters followed, underscoring the need for purification; by the 1860s, British chemist Frederick Augustus Abel addressed this through a patented stabilization process in 1865, involving extended washing (up to four days) and mechanical pulping to remove impurities and achieve uniformity, enabling safer large-scale production.

Development in Film and Fabrics

In 1869, American inventor developed , the first commercially successful derived from nitrocellulose mixed with , marking a pivotal advancement in synthetic materials for consumer products. This innovation addressed the need for substitutes, particularly for billiard balls, which had become scarce due to overhunting of , and extended to everyday items like detachable shirt collars and cuffs that provided a stiff, polished appearance without the maintenance of natural fabrics. Hyatt's patent (U.S. #88,633) enabled , transforming nitrocellulose from its earlier unstable guncotton form into a versatile, moldable plastic that revolutionized . The application of nitrocellulose in textiles emerged in the late , particularly through French Hilaire de Chardonnet's 1884 process for producing "artificial silk" by extruding nitrocellulose solutions into filaments, which were then denitrated to create a silk-like . This nitrocellulose-doped silk gained popularity in the 1890s to 1920s for , offering a cost-effective alternative to natural with enhanced durability and resistance to wrinkling due to the material's inherent stiffness and smooth finish. Widely used in dresses, blouses, and undergarments, it allowed for lightweight, lustrous garments that maintained shape during wear, though its flammability posed challenges in everyday use. Production peaked in and the U.S. before safer alternatives diminished its role. Nitrocellulose's role in the film industry accelerated with Thomas Edison's 1891 , an early motion picture viewer that utilized 35mm cellulose film strips coated with , establishing the standard format for moving images and sparking the boom. This highly flammable yet sensitive base material enabled clear, high-contrast projections, fueling the growth of cinema from peep shows to theatrical screenings worldwide through the early . Its widespread adoption persisted until 1951, when safety standards mandated the shift to non-nitrate bases following numerous theater fires and degradation issues, effectively ending nitrocellulose's dominance in motion picture stock. Commercial scaling of nitrocellulose film production in the 1920s was led by , which entered the market in 1926 through partnerships like Pathé Exchange to supply Hollywood studios amid rising demand for feature films. 's facilities in , produced high-quality 35mm stock that supported the era's expansion, with output reaching millions of feet annually to meet global needs. This industrial effort not only stabilized supply but also refined manufacturing to mitigate instability, solidifying nitrocellulose's temporary legacy in visual media before safety regulations curtailed it.

Shift to Modern Alternatives

The dangers associated with nitrocellulose-based nitrate film, particularly its high flammability, prompted the film industry to transition to safer alternatives in the early . In 1909, Eastman Kodak introduced as a "safety" film base for still photography , aiming to mitigate the risks of and rapid burning inherent to cellulose nitrate. This innovation was commercialized for motion picture applications in the , with diacetate safety film gradually replacing nitrate stock. By the 1930s, a series of devastating nitrate film fires accelerated the adoption of , leading to widespread industry mandates for safety film and Kodak's complete retirement of nitrate production by 1952. In the realm of explosives and propellants, post-World War II advancements reduced dependence on pure nitrocellulose formulations through the development of triple-base powders. These propellants combine nitrocellulose with and , the latter first incorporated as an component during WWII to lower temperature and while maintaining energy output. Introduced in the late , triple-base compositions typically feature a lower proportion of nitrocellulose—often around 30-50% compared to 50-60% in double-base variants—allowing for enhanced barrel life and reduced erosion without sacrificing performance. This evolution diversified propellant chemistry, limiting nitrocellulose's role to a supporting energetic base in modern military applications. Environmental regulations in the 1970s further drove the decline of nitrocellulose in coatings and adhesives, particularly lacquers. The U.S. Clean Air Act Amendments of 1970 and subsequent EPA rules targeted volatile organic compounds (VOCs), imposing strict limits on solvent emissions from ambient-curing paints; nitrocellulose lacquers, which require high-VOC organic solvents for dissolution, exceeded these thresholds and faced phase-out pressures. This spurred the industry shift to water-based acrylic emulsions, which use water as the primary carrier and emit far fewer VOCs, offering comparable durability with improved environmental compliance. By the , waterborne acrylics had largely supplanted nitrocellulose lacquers in automotive and wood finishes. Today, nitrocellulose retains niche roles in printing inks, pharmaceuticals, and specialized propellants, but its overall use has diminished in legacy sectors like motion picture film and solvent-based coatings, where safer synthetics dominate. Global nitrocellulose market value, reflecting production for these remaining applications, stood at approximately USD 1.1 billion in 2024 and is projected to grow to USD 1.6 billion by 2030. During , stabilized nitrocellulose-based propellants were crucial for artillery shells, underscoring its pivotal military role before the post-war innovations that led to modern alternatives.

Safety and Hazards

Fire and Explosion Risks

Nitrocellulose exhibits extreme flammability due to its , which facilitates rapid oxidation and decomposition upon ignition. Its is approximately 170°C, allowing it to spontaneously combust under moderate conditions without an external . Once ignited, nitrocellulose burns intensely, producing its own oxygen and generating temperatures up to 1700°C, making it difficult to extinguish with conventional means like or . In applications, the material's thin structure enables rapid propagation, contributing to uncontrolled spread in storage or projection environments. Historical incidents underscore the severe explosion and fire risks associated with nitrocellulose-based materials, particularly nitrate film. On July 9, 1937, a fire at the storage vaults in , destroyed approximately 40,000 reels of nitrate film, accounting for over 75% of the studio's pre-1930 productions, including many silent films and early talkies; the blaze, fueled by the self-sustaining combustion of nitrocellulose, resulted in one death and two injuries. Similarly, the June 13, 1914, explosion and fire at the Lubin Manufacturing Company's vaults in obliterated a substantial portion of the studio's film library through of nitrate stock, highlighting the material's propensity for catastrophic ignition in confined spaces. To counteract these hazards, nitrocellulose formulations often incorporate stabilizers such as at levels of 0.5-2% by weight, which react with byproducts to prevent autocatalytic acceleration of degradation and reduce the likelihood of spontaneous ignition. Safe storage practices are further enforced by NFPA 40, the Standard for the Storage and Handling of Cellulose Nitrate , which restricts quantities to approved cabinets (e.g., no more than 750 pounds of per cabinet), mandates non-sparking tools and electrical equipment, and requires dedicated ventilation systems to disperse heat and gases. These measures collectively minimize risks during handling and long-term preservation.

Health and Environmental Impacts

Nitrocellulose itself exhibits low , with oral LD50 values exceeding 5,000 mg/kg in rats and mice, but its products pose significant health risks during handling and processing. Inhalation of nitrogen oxides (NOx) generated from can lead to , a condition where is oxidized and impairs oxygen transport in the , as observed in cases of occupational exposure to nitrocellulose and related compounds. Additionally, nitrates derived from nitrocellulose breakdown contribute to toxicity, with animal studies reporting oral LD50 values for around 2,600 mg/kg in rats, though forms are more potent at approximately 180-200 mg/kg in mice. Purification residues from production may introduce trace impurities that exacerbate these effects, but primary concerns stem from decomposition byproducts. Contact with nitrocellulose lacquers often involves solvents that cause and eye irritation, manifesting as redness, stinging, and swelling upon exposure. Safety data for nitrocellulose lacquers classify them as causing serious eye damage (Category 2A) and mild irritation, with symptoms including burning and from prolonged contact. Chronic occupational exposure among workers in and coatings industries is associated with respiratory issues, including irritation of the and , obstructive lung patterns, and reduced function, linked to repeated of solvent vapors and particles. Studies on factory workers show higher prevalence of airflow obstruction and from long-term fume exposure, underscoring the need for protective measures in industrial settings. Environmentally, nitrocellulose is generally non-biodegradable under standard aerobic conditions due to its structure, persisting in waste streams and contributing to long-term if not properly managed. In applications like paints and coatings, it drives (VOC) emissions, with nitrocellulose-based formulations typically releasing 480-640 g/L of VOCs during application, which degrade air quality and form . of nitrocellulose waste produces and other gases, with yielding CO2 emissions roughly proportional to its carbon content, often exceeding the material's mass when accounting for full oxidation products like CO2 and . The U.S. Agency (EPA) regulates effluents from manufacturing processes, including those involving nitrocellulose, under effluent guidelines for explosives production, requiring reductions through methods like biodenitrification to limit discharges to below 10 mg/L for nitrates in sources. Recent studies in the have identified microbial pathways for nitrocellulose breakdown under anaerobic conditions, offering potential for sustainable disposal. For instance, specific in anaerobic environments can degrade nitrated cellulose into and simpler compounds, achieving partial mineralization through processes. Research on samples demonstrates up to 80-90% reduction via microbial activity, suggesting as a viable alternative to for reducing environmental persistence. These advancements highlight evolving strategies to mitigate nitrocellulose's while complying with regulations like EPA limits on .

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