Перевести .. прочтите и переведите письменно текст. rubber natural rubber is an elastic substance found as milky dispersion in many specics of plants. synthetic rubbers are highly polymeric substances manufactured from a wide range of chemical compounds. both synthetical and natural rubber have in common the ability to undergo nearly reversible, highly elastic deforma¬tion. , f in 1960, world wide use of rubber was divided nearly equally between natu¬ral product (about 2 million tons) and synthetic rubr ber (about 1,8 million tons). natural rubber being an extremely valuable substance, many other naturally occurring compounds are closely related to it,chemically. the basic building block for natural rubber as well as other polyisoprenoids is acetic acid. natural rubber was first obtained from wild trees in brazil. the physical and chemical properties of natural rubber are fixed by biologi¬cal factors. in synthetic rubber a much greater variation of properties can be real¬ized. the chemical properties of rubber are of paramount importance. vulcanization is a process used jto make raw rubber useful. it decreasessen- sitivity to extremes of temperature, confers resistance to flow under stress and sta¬bilizes rubbers valuable properties. chemically, vulcanization creates strong bonds between the long linear molecules of the rubbery polymer. it fixes efficiently the molecules position with rcspect to one another and prevents their slippage under¬stress.
