Rubber Polymers

Natural Rubber:

Rubber is an example of an elastomer type polymer, where thepolymer has the ability to return to its original shape after beingstretched or deformed. The rubber polymer is coiled when in theresting state. The elastic properties arise from the its ability tostretch the chains apart, but when the tension is released thechains snap back to the original position.

Natural rubber is an addition polymer that is obtained as amilky white fluid known as latex from a tropical rubber tree.Natural rubber is from the monomer isoprene(2-methyl-1,3-butadiene). Since isoprene has two double bonds, itstill retains one of them after the polymerization reaction.Natural rubber has the cis configuration for the methyl groups.

Charles Goodyear accidentally discovered that by mixing sulfurand rubber, the properties of the rubber improved in being tougher,resistant to heat and cold, and increased in elasticity. Thisprocess was later called vulcanization after the Roman god of fire.Vulcanization causes shorter chains to cross link through thesulfur to longer chains.

The development of vulcanized rubber for automobile tiresgreatly aided this industry.

Link to Polyisoprene -Natural Rubber - with Chime molecule - Macrogalleria at U.Southern Mississippi

Synthetic Rubber - Styrene-Butadiene (SBR):

Some of the most commercially important addition polymers arethe copolymers. These are polymers made by polymerizing a
mixture of two or more monomers. An example is styrene-butadienerubber (SBR) - which is a copolymer of 1,3-butadiene and styrenewhich is mixed in a 3 to 1 ratio, respectively.

SBR rubber was developed during World War II when importantsupplies of natural rubber were cut off. SBR is more resistant toabrasion and oxidation than natural rubber and can also bevulcanized.

More than 40% of the synthetic rubber production is SBR and isused in tire production. A tiny amount is used for bubble-gum inthe unvulcanized form.

Link to SBSRubber - with Chime molecule - Macrogalleria at U. SouthernMississippi

Needle Through a Balloon:

The polymer rubber chains exist in random loose clumps in theunstretched state. At the nipple end of the balloon, there is lotsof rubber and therefore many, many polymer chains - still looselycoiled. These chains can be pierced without popping the balloonbecause the the chains can still be stretched. This is because theyallow the skewer in between the chains without breaking the chainsor the bonds that connect them. But on the sides of the balloon,these chains are stretched almost to their limit and very farapart. The piercing is too much for the stretched chains and theybreak apart., and the balloon pops.