Mankind has been making tools and gadgets from metals for millennia. The discovery of copper and tin ushered in the Bronze Age about 5,000 years ago, and new metal tools swept aside stone tools in a hurry. Iron and steel have been used widely for about 3,000 years, but these days it appears that polymers and plastics are taking over. Nearly everything seems to be made from a material with a weird name like neoprene, polyvinyl chloride, polystyrene, polyethylene, polypropylene, polyacrylonitrile, or polyvinyl butyral. (more...)