Cellulose Acetate

Name:
Cellulose Acetate
Detailed information:

Chemistry name:	(CA).
Properties:
White flakes or powder. A thermoplastic resin, softening at approximately 60–97 C and melting at approximately 260 C. D: 1.27–1.34. Insoluble in acetone, ethyl acetate, cyclohexanol, nitropropane, ethylene dichloride. Notable for toughness, high-impact strength, and ease of fabrication. Subject to dimensional change due to cold flow, heat, or moisture absorption (1–7%). Fibers weaken above 80 C and are difficult to dye uniformly; not attacked by microorganisms.
Derivation:
Reacting cellulose (wood pulp or cotton linters) with acetic acid or acetic anhydride, with H2SO4 catalyst. The cellulose is fully acetylated (three acetate groups per glucose unit), and at the same time the sulfuric acid causes appreciable degradation of the cellulose polymer so that the product contains only 200–300 glucose units per polymer chain. At this point in the process the cellulose acetate ordinarily is partially hydrolyzed by the addition of water until an average of 2–2.5 acetate groups per glucose unit remain. This product is thermoplastic and soluble in acetone. Fibers are produced by forcing an acetone solution through orifices of a spinnerette into a stream of warm air, which evaporates the solvent. Fibers are also produced in a similar manner from cellulose triacetate, which is insoluble in acetone but soluble in methylene chloride.

See Acetate Fiber; Acetate Film.

Available forms:

Sheet, film or fiber, molded items.

Grade:

Filtered and unfiltered. Also graded by percent combined acetic acid content: plastic 52–54%, lacquer 54–56%, film 55.5–56.6%, water resisting 56.5–59%, triacetate 60.0–62.5%.

Hazard:

Flammable, not self-extinguishing, moderate fire risk.

Use:

Acetate fiber, lacquers, protective-coating solution, photographic film, transparent sheeting, thermoplastic molding composition, cigarette filters, magnetic tapes, osmotic-cell membrane.