Polymer such as rubber, suberin, melanin and lignin. Naturally occurring polymers such as cotton, starch and rubber were familiar materials for years before synthetic polymers such as polyethene and perspex appeared on the market. Many commercially important polymers are synthesized by chemical modification of naturally occurring polymers. Prominent examples include the reaction of nitric acid and cellulose to form nitrocellulose and the formation of vulcanized rubber by heating natural rubber in the presence of sulfur. Ways in which polymers can be modified include oxidation, cross-linking and endcapping. Especially in the production of polymers the gas separation by membranes has acquired increasing
Polymer capacitor polymer e-caps in which a solid conductive polymer forms the electrolyte, this is much more difficult to achieve, because its conductivity comes by a chemical process of polymerization. However, the benefits of a solid polymer electrolyte, the significantly lower ESR of the capacitor and the low temperature dependence of the electrical parameters, in many cases justify the additional production steps as well as higher costs. Electrolytic capacitors with the charge transfer salt tetracyanoquinodimethane TCNQ as electrolyte, formerly produced by Sanyo with the trade name "OS-CON", in the true sense of the term "polymer" were not "polymer capacitors". TCNQ electrolytic capacitors