Chemistry Magic 153 



thetic rubbers are copolymers of two or more ingredients 

 mixed in such proportions as to give them rubberlike charac- 

 teristics. Thus a copolymer is a giant molecule formed when 

 two or more unlike monomers are polymerized together. 

 Chemists explain that, if a polymer is like a long train of box- 

 cars, a copolymer is mixed freight boxcars and tank cars 

 alternating in any proportion, such as three boxcars and one 

 tank car (which is the case of butadiene and styrene in 

 Buna S). 



Buna S is called GR-S by officials; the "GR" means simply 

 "Government Rubber." Here is how it is made. Butadiene, a 

 complex gas composed of hydrogen and carbon (obtained 

 from petroleum or alcohol from molasses, corn, or other 

 grains), is mixed with styrene (from coal tar or from petro- 

 leum) in a solution of soapy water. They form a milky liquid 

 latex, similar to that of natural rubber. With heat and the 

 addition of a catalyst (an agent that speeds a chemical reac- 

 tion without being affected itself) the minute droplets are 

 stirred until they change into solid rubberlike particles of 

 Buna S (GR-S). The particles (flox or crumbs) of synthetic 

 rubber rise to the surface of the solution and are screened 

 off. Then they are washed, the excess water is pressed out, and 

 the material is dried and pressed in seventy-five-pound bales. 



Bless John Barleycorn 



There was considerable controversy in 1942 over whether 

 petroleum or alcohol from agricultural products was best for 

 the production of butadiene in the Buna S program. As the 

 program got under way, alcohol proved to be the quickest 

 way to get the synthetic rubber because there were plenty of 

 stills, mostly whiskey, ready to produce it, while the petro- 

 leum industry had to build special equipment. Chemists agree, 

 however, that petroleum alcohol in the long run will prove to 



