332 16.From Natural Fibers to Man-Made Plastics cluding "hard rubber,"which he and his brother Nelson created by extending the heating and sulfurization of caoutchouc.Goodyear died in 1860 and left his widow and six children with $200,000 in debts.In contrast,John B.Dunlop,a British veterinarian,fared much better after he patented and developed (in 1888)the pneu- matic rubber tire based on Goodyear's invention,which eventually made the bicycle popular and had an impact on the automobile in- dustry several decades later.High-performance tires such as for trucks are still produced from this exceptional material. The demand for natural caoutchouc has not decreased in this century despite fierce competition from synthetic rubber,for ex- ample,Buna,neoprene,and methyl rubber.(The latter was al- ready produced in Germany in the 1910s.)We shall return to syn- thetic rubber and other synthetic materials in Section 16.3. Other Organic There is a large number of other natural materials-not neces- Materials sarily fibers-which have been used by mankind over the mil- lennia.Among them is cork,which is harvested from cork oaks (quercus suber)by stripping their bark,boiling it,and scraping off the outer layer.(The trees need to be at least 20 years old but can be stripped again at 8-10-year intervals.)Cork was utilized as early as 400 B.C.,for example,by the Romans for sandals,float anchors,and fishing nets.Bottle stoppers made of cork were in- troduced in the seventeenth century.Today,cork is used for heat- and-sound insulation,linoleum (by mixing cork powder with lin- seed oil and spreading it over burlap),gasket seals,buoys,and household goods.The cork oak is native to the Mediterranean area and is cultivated in Portugal,Spain,Italy,and India. Sponges have been utilized by the ancient Greeks and Romans for applying paint,as mops,and as substitutes for drinking ves- sels.In the Middle Ages,burned sponges were used as medicine. Sponges are primitive,multicellular sea animals which attach to surfaces.They are removed by skin divers from tidal levels to depths of about 70 meters,particularly in the Eastern Mediter- ranean area and on the West coast of Florida. The list of natural materials is not complete with the brief sketch given above.Indeed,it is estimated that in the Western Hemisphere alone,more than 1000 species of plants or parts of plants are utilized in one way or another to create utilitarian products.Most of them,however,are consumed locally or in such small quantities that their mention is not warranted here.Other organic materials,such as animal skin,animal guts,horns, ivory (from elephant or mammoth tusks),straw,bark,reed, shell,amber(fossilized tree resin),etc.,likewise have been used by mankind for millennia and complement the variety of mate- rials which are at our disposal for a more comfortable living.cluding “hard rubber,” which he and his brother Nelson created by extending the heating and sulfurization of caoutchouc. Goodyear died in 1860 and left his widow and six children with $200,000 in debts. In contrast, John B. Dunlop, a British veterinarian, fared much better after he patented and developed (in 1888) the pneu￾matic rubber tire based on Goodyear’s invention, which eventually made the bicycle popular and had an impact on the automobile in￾dustry several decades later. High-performance tires such as for trucks are still produced from this exceptional material. The demand for natural caoutchouc has not decreased in this century despite fierce competition from synthetic rubber, for ex￾ample, Buna, neoprene, and methyl rubber. (The latter was al￾ready produced in Germany in the 1910s.) We shall return to syn￾thetic rubber and other synthetic materials in Section 16.3. There is a large number of other natural materials—not neces￾sarily fibers—which have been used by mankind over the mil￾lennia. Among them is cork, which is harvested from cork oaks (quercus suber) by stripping their bark, boiling it, and scraping off the outer layer. (The trees need to be at least 20 years old but can be stripped again at 8–10-year intervals.) Cork was utilized as early as 400 B.C., for example, by the Romans for sandals, float anchors, and fishing nets. Bottle stoppers made of cork were in￾troduced in the seventeenth century. Today, cork is used for heat￾and-sound insulation, linoleum (by mixing cork powder with lin￾seed oil and spreading it over burlap), gasket seals, buoys, and household goods. The cork oak is native to the Mediterranean area and is cultivated in Portugal, Spain, Italy, and India. Sponges have been utilized by the ancient Greeks and Romans for applying paint, as mops, and as substitutes for drinking ves￾sels. In the Middle Ages, burned sponges were used as medicine. Sponges are primitive, multicellular sea animals which attach to surfaces. They are removed by skin divers from tidal levels to depths of about 70 meters, particularly in the Eastern Mediter￾ranean area and on the West coast of Florida. The list of natural materials is not complete with the brief sketch given above. Indeed, it is estimated that in the Western Hemisphere alone, more than 1000 species of plants or parts of plants are utilized in one way or another to create utilitarian products. Most of them, however, are consumed locally or in such small quantities that their mention is not warranted here. Other organic materials, such as animal skin, animal guts, horns, ivory (from elephant or mammoth tusks), straw, bark, reed, shell, amber (fossilized tree resin), etc., likewise have been used by mankind for millennia and complement the variety of mate￾rials which are at our disposal for a more comfortable living. Other Organic Materials 332 16 • From Natural Fibers to Man-Made Plastics