252 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 7 



available, and at least one such product (butadiene monoxide, a 

 chemical intermediate) has already been announced. 



Styrene production also required for GR-S rubber is carried on by 

 the chemical industry by alkylating benzene with the petroleum olefin 

 ethylene to form ethyl benzene which is converted to styrene by dehy- 

 drogenation. Ethylene is recovered from refinery gases or produced 

 by cracking a petroleum hydrocarbon such as propylene. 



Butyl rubber, another very important synthetic rubber, is a 100- 

 percent petroleum product and a 100-percent American development. 

 It is synthesized from isobutylene, a petroleum hydrocarbon obtained 

 from cracking processes, and a small amount of a diolefin such as iso- 

 prene. These two hydrocarbons are converted into butyl rubber at 

 temperatures of approximately — 150°F. by a continuous process. 

 This development filled the nation's need for heavy-duty inner tubes 

 at a critical time, since GR^S (butadiene styrene rubber) is unsatis- 

 factory and natural rubber was cut off. Butyl rubber in some re- 

 spects is superior to the latter in having better resistance to oxidation 

 and lower permeability to the passage of gases. Inner tubes from 

 it have proved superior to those of natural rubber. This product 

 is expected to have an excellent future. It should find new uses in 

 electrical insulation, waterproof fabrics, and mechanical goods. 



PLASTICS FROM PETEOLEUM 



In the field of plastics there have been some notable products de- 

 rived from petroleum hydrocarbons. Among the newer petroleum 

 plastics are polyethylene resins, allyl plastics, and polyvinylidene 

 chloride resin. Polyethylene resins are a 100-percent petroleum hy- 

 drocarbon resin produced by polymerizing ethylene itself. Their 

 production was announced in 1944 by the duPont Co. and then in- 

 dependently by the Carbide & Carbon Chemicals Corp. Polyethylene 

 plastics are flexible and tough over a wide range of temperatures, 

 have exceptional electrical properties, are resistant to moisture pene- 

 tration, and are chemically inert. They are thermoplastic and can 

 be made into thin sheets and filaments. Polyethylene has been used 

 primarily in electrical insulation for radar equipment. It can be 

 expected to find many uses in a peacetime economy. Its production 

 represents another major technical achievement. 



Allyl plastics are based on allyl alcohol which is derived from 

 propylene. In 1942 two allyl resins were announced, one (diallyl 

 phthalate) by an oil company and the other (now allymer CIl-39) by 

 a chemical company. These plastics are reported to make excellent 

 coating materials for cans and metal containers, one being reported 

 to be less brittle and harder than glass and harder than any other 

 transparent plastic. Its uses have been strictly military. These 

 resins have i^roperties unique to themselves which should make them 



