Science: Inner Tube Substitute

A big missing link in synthetic rubber— a good, plentiful substitute for rubber in inner tubes—appeared last week to have been found. U.S. synthetic rubbers or soft plastics have been developed to do almost every other job that natural rubber can do. Last week aircraft manufacturer Glenn L. Martin announced that his research men had developed a new plastic which makes better inner tubes than nat ural rubber ever did.

The new material, which has no chemical resemblance to rubber, is a vinyl chloride plastic with unusual elastic properties. It contains a plasticizer (unidentified) that enables it to keep its elasticity up to a relatively high temperature (250°F. and it is impervious to sun, water, acids and alkalis. Unlike other plastics, it can be processed on standard rubber-working machinery; unlike rubbers, it does not need to be vulcanized. It is also much easier to make than synthetic rubber; its basic ingredients are coal, air, salt and water.

The inventors of the new plastic, called Marvinol, claim that it has two big advantages over natural rubber for inner tubes : 1) damaged tubes can be traded in and completely reclaimed (since the material is not vulcanized) ; 2) because they are completely impervious to air, Marvin ol tubes do not have to be repumped frequently, like rubber tubes (through which air seeps slowly). Marvinol tubes have so far been tested in 8,000 miles of passenger-car travel (they are not heat-resistant enough for heavy trucks) without needing any reinflation.