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
The Sulphur Institute Symposium. The symposia are attended by producers, consumers, and traders in sulfur, as well as industry service providers, and feature speakers discussing a range of topics relating to sulfur. The 2010 Sulphur World Symposium was held in Doha, Qatar, from April 12 through April 15, 2010. The 2010 symposium featured a tour of the Ras Laffan Industrial City, which is not normally available to the public. Publications by The Sulphur Institute include market studies, industrial publications, general brochures about sulfur, and brochures on the agricultural uses of sulfur. Symposium proceedings are also available. Most publications are available in English, with