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SYNTHETIC PLASTICS 679

for textile sizing and stiffening; for sizing and imparting transparency

to paper; and to make lacquers and paints. Polyvinyl butyral, formed

from polyvinyl acetate by hydrolysis and condensation with butyraldehyde,

is used as an interlayer sandwiched in between plate glass to

form laminated safety glass. The plastic layer stretches under a blow

and holds the broken pieces of glass

together.

One of the most important uses

of "Vinylite" resins developed recently

is in lining "tin" cans for

beverages. "Vinylite" resin-lined

cans completely protect the delicate

flavors in beverages and foods, and

today many well-known canned

products retain their distinctive

flavors because of this transparent

coating of "Vinylite" resins.

"Vinylite" resinous products

have come to be known as the

"versatile plastics" because their

unusual characteristics permit such

a wide range of applications.

Vinyl chloride is made from

acetylene, which is derived from calcium

carbide (coal and limestone),

and hydrogen chloride, which is

obtained from salt and water.

Vinyl chloride is also made from

Fig. 295. A Vinylite fabric work

jacket. (Courtesy of the Carbide

and Carbon Chemicals Corporation.)

ethylene dichloride, which in turn is synthesized from cracked

petroleum gases and chlorine. Acetic acid used to produce vinyl

acetate may be obtained from acetylene or natural gas.

These vinyl resins have a wide range in composition and properties

inasmuch as their molecular weights range from 6000 to 25,000,

depending upon the number of molecules that have joined each other

in the polymerization process.

"Vinyon" fiber is now used to manufacture felt without fur or wool,

in which cotton fibers are mixed with "Vinyon" fibers and then heated

to produce a weblike bonding of the cotton fibers by the "Vinyon"

fiber. Such felts have been found to produce superior filtering media

for filtering liquids and air.

The copolymerized resin is unique because the acetate, with its lower

softening-point, renders the copolymer internally plasticized. Thus

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