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products of chemistry
George 6. Kauffrnan CaliforniaState University, Fresno Fresno, CA 93740
The Rise and Fall of Celluloid Raymond B. ~ e ~ m o u r ' University of Southern Mississippi, Hattiesburg, MS 39406 George B. Kauffman CaliforniaState University, Fresno, Fresno, CA 93740 Pioneer Natural Plastics Before the introduction of Celluloid many common everyday articles such as combs, lantern windows, buttons, buckles, and brush handles were made from horn, hair, hoofs, and other naturally occurring materials. Keratin, the fibrous protein of hair, hoofs, horns, feathers, etc., is a polymer with a high sulfur content. It is insoluble and relatively inert to solvents and chemicals. These naturally occurring plastics can be shaped after being immersed hot wat&then cooled to room temperature. Since synthetic plastics were not invented until the mid 19th centurv. ",these ancient fabrication arts were Dratticed and improved over many centuries. The medieval fabricators were known as horners or hornsmiths. These terms are still used to describe plastics technicians in the United Kingdom. Cow's hoofs were used as a readily available source of solid material in the production of buttons. The economics of this fabrication process was improved during the 18th century by grinding hoofs and forming buttons by hot compression molding. The natural glue present in the hoofs served as an adhesive for these molded buttons. Pioneer Plastic Production in Leominster, MA Decorative combs were fabricated from hoofs in the United States by E. Noyes in West Newbury, MA in 1760. This firm and other comb-making firms were relocated to Leominster, MA, which became known as "comb city" (1, 2). The concentration of comb-making plants in Leominster led to the development of many plastic-making tools that are still in use today in modified form. Due to these localized activities, Lwminster became the pioneer American plastics capital. It is not surprising that the Society of t h e Plastics Industry located its plastics museum in Leominster i n a n abandoned schoolhouse in the mid 1980's.
est and most-desired ivory is ohtained from West African elephants (Loxodanta afncana). Elephants are considered endangered to some extent, and thus are protected. Nonetheless, poachers continue to kill thousands of these animals annually-not for food but for their valuable tusks. Surprisingly, the Scottish missionary and explorer Dr. David Livingstone (1813-1873) believed that the supply of elephants was inexhaustible. However, a century ago, the killing of more than 20,000 elephants was required for the annual consumption of ivory, which exceeded two million pounds. Fortunately, Daniel Spill and Alexander Parkes, in England, and the brothers, John Wesley Hyatt and Isaiah Smith Hyatt, in the United States, attempted to solve the "ivory problem" by inventing suitable substitutes. Synthesis of Cellulose Nitrate The stage was set hy the Frenchmen Henri Braconnot (1781-1855) and Thhphile Jules Pelouze (1807-1867) for the invention of substitutes for ivory. Braconnot f r s t nitrated starch to produce Xyloldine in 1833 (61, and Pelouze nitrated cellulose to produce Pyroxilin (7). However, the pioneer scientific approach was made in Basel, Switzerland by Christian Friedrich Schonbein (179%1868). In 1846 he used a mixture of sulfuric acid and nitric acid as a nitrating agent to produce a cellulose derivative that he called guncotton (Schiesswolk),which he proposed for use as an explosive (8-12). AS shown by the structural formula of the cellobiose repeating unit in cellulose (Fig. I), each repeating unit has
The Ivory Problem While the use of bones, hoofs, and tortoise shells for the production of plastic products has been abandoned, the demand for ivory continues to increase. Objects of ivory carved 20,000 years ago are included in museum exhibitions throughout the world. Despite the low yield of ivory tusk per elephant and laws against ivory poaching and trading. the carvine of ivorv continues in Africa and Asia today T 3 h . Ivorv mav " be ohtained from the tusks and teeth of animals such as the walrus and hippopotamus, but the hard-
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Figure 1. The chair form of the cellobiose repeating unit in cellulose and cellulose trinitrate. Volume 69 Number 4 April 1992
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three hydroxyl p o u p ~ that can each react with a molecule of nitric acid to produce cellulose trinitrate. 1Iowevt.r.due to the crystalline structure of cellulose, some hydroxyl groups are not readily accessible and thus do not react with nitric acid. Cellulose Structure Cellulose is a polydisperse polymer. In other words, it consists of many different molecular homologs that contain 1,750 to 18,000 cellobiose repeating units (13-17). About 85% of t h e hydroxyl groups a r e nitrated by Schonbein's nitrating acid mixture. Concentrated nitric acid, as used by Pelouze, will nitrate only about half of the hydroxyl groups, and dilute nitric acid is even less effective. Schonbein rather than Pelouze is credited with the discovery of guncotton because its only use until the mid 1800's was as a n explosive, and this depends on the content of nitrate ester groups. Guncotton was misnamed nitrocellulose: The nitrogen-containing group present in guncotton is the nitrate group (-ONOz), not the nitro group (-NO.,>. , - -", Manv rotei ins (ex.. keratin) and carbohvdrate ~olvmers (e.g., ciliulose) hav;kgh tensile strength,which is largely due to intermolecular hvdrogen bonding between the hydrogen atoms on one p ~ i ; m e r ~ h a ai nn d k atom on an adjacent chain (nitrogen in keratin and oxygen in cellulose). Due to these relatively strong intermolecular bonds, cellulose is insoluble in water and most organic solvents. Nevertheless, some derivatives of cellulose are soluble in selected solvents because derivative and steric effectsreduce the streneth of intermolecular hvdroeen bonds. The bulkv nitrate &oup in cellulose nitrate teids to separate adjacent ~. o.l w echains. r reduce mrstallinitv. ". and ~romotesolubility. When an average of four hydroxyl groups in each cellobiose repeating unit in cellulose is esterified by nitric acid, the intermolecular attractive force is reduced. Thus movement of the polymer chains is less restricted, and they can slide by each other. This slippage is enhanced by the presence of plasticizers, such as camphor. In contrast, strong intermolecular hydrogen bonds are essential when cellulose, silk, or nylon are used as fibers. Collodion Cellulose and cellulose nitrate are insoluble in common solvents. However, Schonbein discovered that cellulose nitrate is soluble in a 50:50 mixture of ethanol and ether. Yet, credit for the discovery of this solution, which is called collodion, is generally given to J. Parker Maynard, who used it as a coating for wounds and surgical cuts in 1847. Collodion is still used to a small extent, under the trade name Nuskin, for the protection of cuts. However, its principal use was as a vehicle for photosensitive material in "Archetype" photography that was introduced by F. Scott Archer (1813-1878) as an alternative to the daguerreotype process in 1851 (18). Schonbein made brittle films from cellulose nitrate, but the important breakthroueh was the invention of the world's first artificial British inventor Alexander Parkes (18131890) and American inventor J. W. Hvatt (1837-1920). (See Fig. 2.) Contributions of John Wesley Hyatt Hyatt was both an itinerant printer and inventor. One of his inventions was the roller bearing that was named afler him. Other inventions are listed in about 250 patents issued to him hv the U S . Patent Office. The catalyst or carrot responsible for Hyatt's invention of Celluloid was the offer of a $10,000 prize by the firm of
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Fgdre2. .on1 \htse, ? , T I -dj'-'5?( d mc~.lrr..nrnedeveloped Ce .o u Toe Foqar F m s Srn 1 1 Memo a Co ea on. Taden from ref 26, p 33
I'helan and Collander for a useful substitute for the ivory then used for making bllliard balls. Fortunately. Hvatt had developed some exp&se in hot compression &&ding from fabricating dominoes from mixtures of cellulose and shellac. He used these techniques in 1870 in molding Celluloid, his trademark for a plastic consisting essentially of a solid solution of cellulose nitrate and camphor, which was added as a plasticizer (19-25). According to Louis Pasteur (1822-18951, "Chance favors the prepared mind." This phrase may be applied to the invention of Celluloid. Unlike his British contemporary Daniel Spill (1832-18931, who used mixtures of collodion and camphor to produce Xylonite (26-28), Hyatt investigated various mixtures of solid cellulose nitrate and camphor. In his 1914 Perkin Award acceptance speech (29) Hyatt emphasized that the solid deposited from collodion contained as much as 75% residual solvent. Thus he opted to use mechanical means tQ produce Celluloid. Among the many unique products empirically developed imperatively hy I I y ~ twere t odlodion-cwted ci~mpositehilliard balls and molded composites of ivorv dust and cellulose nitrate. His best compositions for ~eiluloidwere prepared by evaporating aqueous mixtures of cellulose nitrate and camphor, then molding the residue with heat and pressure. In 1854 J.Cutting patented mixtures of camphor and collodion (30). Plasticizer Technology Camphor is a white solid ketone with the empirical formula CloHaO. It is obtained by the steam distillation of wood of the Formosan (Taiwanese) tree Cinnamomum camphora. I t is used as a flexibilizing agent or plasticizer (3032) to reduce the intermolecular forces between the polymer chains, such as those in cellulose nitrate. Cellulose nltrate and polyvinyl chlonde (PVC, (331 had httle use untd thev were dastlc~zedDr Waldo Llonsbuw Semon (born 1898) pro&ced flexible PVC in the mid 1920's by adapting Hyatt's ~lasticizingtechniques to produce Koroseal (Goodrich)by the addition of liquid tricresyl
ohomhate. Althon~hSemon had no difficulty convincing plastks technicianiat the B. F. Goodrich company to mold his flexibilized PVC, no molder would agree to the molding of a mixture of camphor and guncotton until Hyatt reduced the explosiveness of Celluloid by the addition of a small amount of ethanol. Unfortunately, this formulation change conflicted with Hyatt's high-solids concepts.
of Parkes and S~ill Contributions - Hyatt's contemporary British competitors, Parkes (34) and Soill, were better scientists than he. Parkes, who inwas a chemist, metallurgist, andinvented ~ i r k e s i n (351, e ventor, who was apprenticed to a brass works in Birmingham, England. While working with the firmof Elkington and Mason and with the approval of his employer, he sought to develop a new product that, like ivory, could be fabricated like metal or wood. He investigated the properties of the residue formed by evaporating collodion containing %20% camphor, a process which he claimed dated back to 1835. However, he failed to mention the use of camphor in any of his numerous patent applications. Soill. who was trained a s a physician, cited the use of e q A l parts of camphor and celiulose nitrate in his patent a o ~ l r a t l o nin 1860. L'nfortunately, Parkes also added cast& oil to the Parkesine composition. Since these products were not useful, his company failed in 1866. However, Daniel Spill joined forces with his brother George to establish George Spill and Company, which produced water~ r n o ftextiles in com~etitionwith Mackintosh rainwear. ~~~However, he continued his interest inxylonite, and he was manted five Datents on mixtures of cellulose nitrate and camphor. Despite the lack of success with Parkesine, Daniel Spill joined with American inventor Levi P. Merriam (18291889) in 1876 to establish the X y l 0 ~ t eCompany, which also had limited success. The use of X y l o ~ t edetachable shirt fronts (diekeys), collars, and cuffs, which were called "American linen", knhanced its production and assured the Xylonite Company's success. &
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F +re 4 A Ce jlofo p box arl examp e 01 me resd 1s Inat could be ach wed w lh !he llrsl commerc a y aval ab c piasl c Note the h e dela of thc gfr s face C o ~ t l ~ hartona sf M-se-m of Anler can h s. lory. Sm lnsonaan InstLt on Ta
