682 CREATIVE CHEMISTRY Fig. 297. A tongue depressor made of curved "Lucite" methyl methacrylate plastic. (Courtesy of the E. I. du Pont de Nemours Company.) with minimum distortion and are thus used in transmitting speech through flexible conduits. Polyvinyl alcohols are used in photolithographing printing. A solution of polyvinyl alcohols, sensitized to light by adding ammonium or potassium dichromate, is coated on a zinc plate. This plate is then "exposed" like other photographic plates and developed by simply washing in water. The nonexposed portions are soluble in water, while the exposed portions are rendered insoluble by the action of the light and remain on the plate to form the printing surface. Polyvinyl alcohols may be used as an emulsifier in making such cosmetic products as cold creams, brushless shaving creams, cleansing creams, and beard-setting preparations for use with electric razors. They also increase the sticking and spreading power of insecticide sprays and, when coated on glass, make it nonfogging under conditions of high humidity inside and low temperatures outside of a room. " Super-glass " Is Now Made from Polymethyl Methacrylate. A few years ago one of the felt needs was an organic "glass." Today we have in polymethyl methacrylate a product clearer than optical glass, weighing half as much, which may be cut, turned, sawed, carved, drilled, polished, shaped, formed, and swaged. It is flexible, durable, and strong, and may be given translucent, opaque, or pearl color effects. This product, sold under the names of "Lucite" methyl methacrylate plastic, "plexiglass," or "Crystalite," is derived ultimately from air, water, and coal or Fig. 298. Printed material shown through a 93^2 inch thickness of "Lucite" meth}! methacrylate plastic. (Courtesy of the E. I. du Pont de Nemours Company.)
SYNTHETIC PLASTICS 683 natural gas. The usual raw materials employed in producing acrylic acid derivatives are ethylene chlorhydrin and acetone, which are obtained from the hydrocarbons contained in the gases produced in the cracking of petroleum. It transmits light through its own curves, while conducting practically no heat, and thus finds applications where light is to be "piped" in medical and dental appliances. It is used in making automobile reflectors, furniture, shoes, dashboard panels, radiator ornaments, vanity cases, and a host of other products. Lenses for cameras and eye glasses can be made by molding them out of this plastic material much cheaper than optical glass Fig. 299. Dashboard of car with panels of "Lucite" methyl methacrylate plastic. (Courtesy of the E. I. du Pont de Nemours Company.) can be ground, but they were not yet in commercial production in 194L This type of plastic is thermoplastic and may be bent and shaped by softening it in hot oil at temperatures varying from 285° F. to 315° F. Soya Beans and Milk Now Compete with Coal as a Raw Material in the Production of Plastics. Two Japanese chemists have produced from soya beans a strong synthetic fiber which shows a possibility of competing with silk and wool. Italy was the original home of synthetic wool fibers, made from casein, the protein of milk. This product is called "lanital." To produce "lanital," casein is dissolved in an alkaline solution, aged, and extruded into an acid bath, where it is precipitated. It is then hardened with formaldehyde. Lanital is very similar to wool in some respects. Casein wool is marketed in the United States under the name " Prolon." Casein has been combined with formaldehyde to make plastics for billiard balls, buttons and buckles, and other products. An average cow produces enough casein each year to produce one hundred pounds of lanital. Fifteen million pounds of casein are used each year for the preparation of casein paints. The Ford Motor Company has developed a fiber from soya beans.