Polymer science be considered polymer science in the modern sense. In the 1840s, Friedrich Ludersdorf and Nathaniel Hayward independently discovered that adding sulfur to raw natural rubber (polyisoprene) helped prevent the material from becoming sticky. In 1844 Charles Goodyear received a U.S. patent for vulcanizing natural rubber with sulfur and heat. Thomas Hancock had received a patent for the same process in the UK the year before. This process strengthened natural rubber and prevented it from melting with heat without losing flexibility. This made practical products such as waterproofed articles possible. It also facilitated practical manufacture of such rubberized materials. Vulcanized rubber
Rubber band approximation) that elastic polymers do not store any potential energy in stretched chemical bonds. No elastic work is done to "stretch" molecules when work is done upon these bulk polymers. Instead, all work done to the rubber is "released" (not stored) and appears immediately in the polymer as thermal energy. Conversely, when the polymer does work on the surroundings (such as contracting to lift an object) it converts thermal energy to work in the process and cools in the same manner as an ideal gas, expanding while doing work. In the UK during 2004, following complaints from the public about