Plastics' Progress

When the war began, plastics were far past the gadget stage. They were passing the stage of being chiefly substitute materials. Now, pushed by wartime technology, plastics are major materials in their own right. There are many new types, and plastics are preferred for many jobs. The full catalogue would be long and complex. Suggestive items:

> A whole new family of plastics is based on the element silicon, rather than the element carbon which provides the chemical skeleton for the majority. These "silicones" are the result of research by Corning Glass Works (glass might be called a silicon plastic) and engineering by Dow Chemical Co. First uses, undoubtedly military, have not been disclosed. The silicones, solid or liquid, have one extraordinary property: an ability to stand extreme temperatures characteristic of their silicon parentage.

> For use in meters, Mellon Institute has developed two plastics: a leatherlike material which is expected to stand up for 25 years without stretching even if flexed 900 times an hour; a metallike material which can stand spinning in a stream of hot or cold water for the same length of time without swelling, shrinking, or appreciable wear.

>Thermo-Cast, developed in Columbia University laboratories, speeds aircraft production. A plastic that acts like a metal, it may be melted and cast without pressure. Thermo-Cast is tough enough, although one-fifth the weight of steel, to stand up in dies used to shape aluminum sheets. By stamping larger sections, the number of rivets needed is reduced, assembly time is speeded.

> Today's troops may awake to the blast of a bugle molded completely of plastic, brush their teeth with paste from a plastic tube, drink from a plastic canteen. In testing plastics for canteens, the Army Quartermaster Corps set higher standards than previous materials could meet. Tests include freezing the canteen while 90% full of water, dropping it ten feet onto concrete, tasting and smelling distilled water kept in the canteen 24 hours at tropic heat.

> Lucite plastic bearings in a giant citrus-juice extractor are lubricated by the juice they squeeze, are not affected by the sterilizing steam and the fruit acids, which wear down bronze.

> Pilots and gunners were severely sunburned in early plastic airplane enclosures; new plastics screen out the ultraviolet rays intense at high, clear altitudes.

> Newest use of the oldest plastic (cellulose nitrate) is for storage-battery housings. Designed for portable searchlights on war duty, the new batteries point toward postwar automobile batteries that are lighter, tougher, and so transparent that the level of the liquid may be checked at a glance.

Nonskid, chatter-proof false teeth are a postwar promise. Secret of their soundproofing: acrylic plastic, which is durable but not so hard that it clacks.

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