Cellulose Acetate

Cellulose acetate is a chemically modified form of cellulose. In chemical terms, it is the acetate ester of cellulose, which is a biopolymer obtained from cotton or tree pulp.

Cellulose acetate is used as a synthetic fiber, a film base in photography, and a component in some adhesives. The fiber, which is often blended with other materials (such as cotton and silk), is used extensively in clothing, draperies, upholstery, diapers, and filters.

History

Cellulose acetate was first introduced in 1904 by Camille Dreyfus and his younger brother Henri, based on chemical experiments they had performed in a shed in their father's garden in Basel, Switzerland. Given their father's interest in a chemical factory, his influence was probably a factor in their choice of careers. Basel was a center of the dyestuffs industry, and their first achievement was the development of synthetic indigo dyes. In search of a field that offered limitless possibilities, they chose to make cellulose acetate products, including fibers for textile use.

For five years, the Dreyfus brothers studied and experimented in a systematic manner in Switzerland and France. By 1910, they had perfected acetate lacquers and plastic film and opened a factory in Basel capable of producing about three tons a day. The film was sold largely to the celluloid industry in France and Germany, and to Pathe Fréres in Paris for nonflammable motion-picture film base. A small but growing amount of acetate lacquer, called "dope," was sold to the expanding aircraft industry to coat the fabric covering wings and fuselage.

By 1913, the brothers produced excellent laboratory samples of continuous-filament acetate yarn. The outbreak of the First World War postponed commercial production of the yarn until 1921. The war necessitated rapid expansion of the Basel factory, which terminated its trade with Germany and exclusively supplied the Allied Governments with acetate "dope" for military aircraft.

In November 1914, the British Government invited Dr. Camille Dreyfus to come to England to manufacture acetate "dope." In 1917, the War Department of the U.S. government invited him to establish a similar factory in the United States. After about six weeks, a contract was negotiated for sale of acetate "dope" to the War Department and a plant site was sought. Dr. Dreyfus and his associates started construction of the American company at Cumberland, Maryland in 1918, but the war was over before the plant could be completed. Nonetheless, construction of the plant continued, the early management team began to assemble, and the organization in England completed development of the first commercially successful acetate textile yarn.

In 1921, the British company produced the first commercial cellulose acetate yarn. It was sold primarily for crocheting, trimming, and effect threads and for popular-priced linings. The first yarn spun in America was on Christmas Day, 1924, at the Cumberland, Maryland plant. It was trademarked as Celanese.

The first yarn was of fair quality, but sales resistance was heavy, as silk associates worked zealously to discredit acetate and discourage its use. Acetate, however, became an enormous success as a fiber for moiré, because its thermoplastic quality made the moiré design absolutely permanent. The same characteristic also made permanent pleating a commercial fact for the first time, and gave great style impetus to the whole dress industry.

The mixing of silk and acetate in fabrics was accomplished at an early stage, and almost at once cotton was also blended. As a result, it became possible to produce low-cost fabrics by using a fiber that was cheaper than silk or acetate. Today, acetate is blended with silk, cotton, wool, nylon, and other materials to provide fabrics with excellent wrinkle recovery, good handling and draping qualities, quick-drying ability, proper dimensional stability, and cross-dye pattern potential, at a very competitive price.

Cellulose acetate film

Cellulose acetate (triacetate) photographic film was introduced in 1934 as a replacement for the unstable and highly flammable celluloid film stock that had previously been standard. In addition, acetate film became the base for magnetic tape prior to the advent of polyester film.

The disadvantage with acetate film is that it deteriorates in the presence of oxygen to an unusable state, releasing acetic acid. This is known as the "vinegar syndrome." For this reason, polyester film stock (sometimes referred to under Kodak's trade name "Estar") has become more commonplace since the 1980s, particularly for archival applications. Acetate film stock is still used in some applications, such as camera negative for motion pictures.

Production

The Federal Trade Commission defines acetate fiber as "A manufactured fiber in which the fiber-forming substance is cellulose acetate. Where not less than 92 percent of the hydroxyl groups are acetylated, the term triacetate may be used as a generic description of the fiber."

Steps in the production process:^[1]

• 1) Cellulose is purified from wood pulp or cotton linters.
• 2) This cellulose is mixed with glacial acetic acid, acetic anhydride, and a catalyst (sulfuric acid).
• 3) The mix is allowed to age for 20 hours, when partial hydrolysis occurs (and sulfate groups are removed).
• 4) Cellulose acetate is precipitated as acid-resin flakes.
• 5) The flakes are dissolved in acetone (a volatile solvent).
• 6) The solution is filtered.
• 7) The spinning solution extruded in the form of filaments in a column of warm air. The solvent evaporates and is recovered.
• 8) The filaments are stretched and wound onto beams, cones, or bobbins ready for use.

Acetate versus triacetate fibers

Cellulose acetate and triacetate fibers are mistakenly thought of as the same product. Although they are similar, their molecular structures differ. Triacetate is known as the generic or "primary" acetate, containing no hydroxyl (OH) group. Cellulose acetate fiber, by contrast, is known as a modified or "secondary" acetate containing a few hydroxyl groups. It is often referred to simply as "acetate."^[1] Triacetate fibers are no longer produced in the United States.

Fiber Properties

Acetate is a valuable manufactured fiber that is low in cost and has good draping qualities. Given its properties, it has been promoted as the “beauty fiber”.^[1] It is used in fabrics such as satins, brocades, and taffetas to accentuate luster, body, drape, and beauty.

• Bonding: the fibers are easily bonded with plasticizers, under heat and pressure.
• Solubility: acetate is soluble in many common solvents (such as acetone) and can be modified to be soluble in alternative solvents, including water.
• Interaction with water: acetate wets easily; in textile applications, it provides comfort and absorbency, but also loses strength when wet.
• Feeling by hand: soft, smooth, dry, crisp, and resilient.
• Comfort: breathes, wicks, dries quickly, no static cling.
• Drape: linings move with the body, conform to the garment.
• Color: deep brilliant shades with atmospheric dyeing meet colorfastness requirements.
• Luster: light reflection creates a signature appearance.
• Performance: colorfast to perspiration staining, colorfast to dry cleaning, air and vapor permeable.
• Environmentally friendly:
  • made from wood pulp of reforested trees.
  • can be composted or incinerated.
• Abrasion: poor resistance
• Heat retention: poor thermal retention
• Allergenic potential: none (it is hypoallergenic).
• Dyeability: Special dyes and pigments are required because acetate does not accept dyes ordinarily used for cotton and rayon. Two methods are used: in the cross-dyeing method, yarns of two different fibers are woven into a fabric in a desired pattern; the solution-dying method provides excellent color fastness under the effects of sunlight, perspiration, air contaminants and washing.^[1]

Major industrial acetate fiber uses

• Apparel: linings, blouses, dresses, wedding and party attire, home furnishings, draperies, upholstery, and slip covers.
• Industrial uses: cigarette filters, ink reservoirs for fiber-tip pens.
• High-absorbency products: diapers, surgical products, and other filters.
• Toys: the original Lego bricks, made from 1949 to 1957.

See also

• Celluloid
• Plastic
• Polymer
• Textile

Notes

References

ISBN links support NWE through referral fees

• Acetate fiber Fibersource.com.
• Kadolph, Sara J. and Anna L. Langford. 2001. Textiles, Ninth Edition. Upper Saddle River, New Jersey: Pearson Prentice Hall. ISBN 0130254436