Science: Rubber from Rubber

As scrap rubber piled up in reclamation heaps last week, many a citizen wondered how—and even whether—you could separate the rubber from a raincoat. It is possible and simple, explained rubber technologists last week.

In rubber-reclaiming plants the scrap is first sheared and hashed into tiny pieces.It is then sifted past magnets, which draw out any bits of iron. Next it is dumped into a "digester" tank where 1) caustic soda (sodium hydroxide) is added to destroy all cloth fibers and to remove free sulfur (added originally in vulcanizing); 2) coal-tar oils are added to soften the rubber. These added chemicals and decomposed fibers are rinsed out in water sprays and settling tanks. At last the rubber is squeezed into heavy sheets and baled for reprocessing.

Sometimes this reclaimed solid crude is further reduced to a liquid latex. It is kneaded in water with a soapy "dispersing agent" until the rubber molecules lose their attraction for each other and disperse to form an even suspension in the water. From such latexlike dispersions are made heavy, industrial rubber gloves and other dipped articles, as well as rubberized fabrics like raincoats.

Working frantically since Pearl Harbor, U.S. rubber companies have greatly increased their production of reclaimed rubber. They have also streamlined the reclamation process so that it often takes only ten hours instead of last year's 16.

Yield of rubber from different articles varies greatly: 100 lb. of crude can be reclaimed from 140 lb. of inner tubing, 165 lb. of bathing caps and shoes, or 175 lb. of hot-water bags. Some 94 tons of rubber gloves can yield the 75 tons of crude used in building a large warship. Five old overshoes are enough for one Army raincoat.