Polyisoprene is the polymer known as natural rubber, although it can also be manufactured. The natural rubber latex is harvested from the rubber tree, Hevea brasiliensis. This substance has a variety of natural additives, such as proteins and sugars. The polymer from the natural latex is resistant to many solvents and also is easily processed. The synthetic form of this rubber is produced from a pure isoprene solution with a stereospecific isomer to produce the more commonly used cis-l,4 isomer. These rubbers are resistant to abrasion and most solvents and are commercially used in automobile tires, adhesives, and a variety of products that come in close contact with the general public. Their use in baby bottle nipples is a good indication of the extremely low toxicity associated with these elastomers.
