234 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1941 



These remarkable properties make styrene resin exceptionally well 

 suited for radio-frequency insulation. Its transparency and chemical 

 resistance are responsible for most of its other uses, such as bottle 

 closures, refrigerator trim, automotive accessories, and indirect light- 

 ing of mileage and other indicators. 



Acrylic resins. — The acrylic resins were jQrst prepared industrially 

 in America in 1931 for use in coatings and as a binder for laminated 

 glass. The better-known and very interesting methyl methacrylate 

 resin is a product of more recent origin. The cast resin, called Plexi- 

 glas and Lucite, respectively, by its two manufacturers, reached the 

 production stage during 1937-38. The airplane industry has found 

 these cast sheets particularly well adapted to their requirements for 

 gun turret and cockpit enclosures because of their lightness, weath- 

 ering resistance, nonfragility, and clarity. The resin's high internal 

 reflection makes possible spectacular and useful lighting effects in 

 edge-lighted signs and dental and surgical instruments. This type of 

 resin has been found to be preeminently suited for dentures. Its 

 optical qualities make it suitable for spectacle and camera lenses and 

 for reflectors for indirect highway lighting. 



Cellulose acetate hutyrate. — The Hercules Powder Co. introduced 

 this material in 1932 as a protective coating base. The Tennessee 

 Eastman Corporation started manufacture of a cellulose acetate 

 butyrate molding composition in 1938 and designated it as Tenite II, 

 the original Tenite being their cellulose acetate molding compound. 



Cellulose acetate butyrate compositions are superior to cellulose 

 acetate plastics in weathering resistance and in freedom from warp- 

 ing. The requisite plasticity can be produced with a relatively low 

 percentage of plasticizer and with comparatively nonvolatile and 

 water-insoluble plasticizers. The applications of cellulose acetate 

 butyrate plastic are primarily such as result from its combination of 

 toughness and resistance to weathering, for example, woven furniture 

 for exterior use, automobile accessories, and fishermen's equipment. 

 Its record of achieving new applications during 1940 was outstanding 

 among the plastics. 



Ethylcellulose. — The first cellulose ether to be made commercially 

 in America was ethylcellulose. The Hercules Powder Co. began 

 making it in 1935 and the Dow Chemical Co. undertook its manu- 

 facture in 1937, marketing their product under the trade name Etho- 

 cel. Ethylcellulose plastic has not as yet come into general use for 

 molded parts. Its chief applications to date have been in protective 

 coatings, adhesives, paper and fabric coatings, wire insulation, and 

 extruded strip. Another cellulose ether, methylcellulose, was an- 

 nounced by the Dow Chemical Co. late in 1939. Methocel, as it is 

 called, is water soluble, odorless, tasteless, and nontoxic. It yields 

 films which are greaseproof and highly flexible. 



