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 working with representatives in India to encourage similar growth in sulfur usage. TSI worked with the International Fertilizer Industry Association and the Fertilizer Association of India to provide activities and resources on the use of sulfur in agriculture. TSI serves as a spokesperson for the sulfur industry with its Transportation Regulations and Logistics program. "TSI monitors for proposed changes to regulations impacting transportation and handling of sulfur and sulfur compounds." Their program covers transportation by rail, road, and sea transportation on regional, national, and international levels. The Sulphur Institute holds an international symposium annually titled The Sulphur Institute's Sulphur World