Cellulose Acetate (CA)
Properties and Applications
Cellulose acetate (CAc, CA) and its co-esters are the most
important esters of cellulose.1 CAc is a crystal clear,
tough, and flexible plastic and one of the most stable cellulose
derivatives. It has excellent chemical resistance to organic and
inorganic weak acids, hydrocarbons, vegetable oils, and the like.
Unlike cellophane, it is thermoplastic and
easier to process.
Films made of this plastic have exceptionally low haze, high moisture vapor transmission but low water permeability.
Pure CAc is obtained by acetylation of the cellulose hydroxyl
groups with acetic anhydride in acetic acid and in the presence of
a strong acid catalyst. CAs can be broadly classified into two types:
cellulose diacetate (CDA) and cellulose triacetate
(CTA). The former has a degree of acetylation of about 2.4 and the latter of
about 2.9, respectively. The two types of CAc have somewhat different physical properties;
in general, the gas and moisture permeability decreases with increasing acetyl content, whereas the chemical resistance increases.
Often plasticizers are added or
mixed ester of cellulose like cellulose acetate-butyrate (CAB) and
cellulose acetate-propionate
(CAP) are produced which have improved flexibility, toughness, and moisture resistance.
Cellulose acetate is widely used for industrial and consumer goods
applications. Important uses include textiles (fibers and threads for quality fabrics); plastic films such as optical film for LCD technology and antifog goggles; and consumer products such as cellulose based filters,
window cartons, and labels. One of the most important uses of
CAc, CAB
and CAP resins is in coatings including metal and wood coatings, gravure and flexographic printing inks, graphic arts, ink jet printing inks,
automotive clear coats, and general industrial coatings. Cellulose
ester resins, in particular the mixed esters are beneficial in reducing surface defects such as cratering, fish eyes, and organge peel in various
resin systems including melamine-acrylic clearcoats.
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1According to MarketeandMarkets™, the cellulose acetate market is expected to grow from USD 3.6 Billion in 2016 to USD 4.9 Billion by 2022.
Source: marketsandmarkets.com, April 2018.