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Article: Precautions needed to compound insoluble sulfur: Part 1 of 2.(Technical)
- Article from:
- Rubber & Plastics News
- Article date:
- September 23, 2002
- Author:
CopyrightCOPYRIGHT 2002 Crain Communications, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Byline: Byron H. To, Arie De Hoog
Ordinary sulfur used for rubber compounding is in the stable, rhombic form, which is soluble in rubber hydrocarbons at processing and vulcanization temperatures. As temperatures rise during mixing, more sulfur is dissolved in the rubber. Fig. 1 gives the solubility of sulfur in several polymers. However, at storage temperatures, the ordinary sulfur is only partially soluble. Therefore, as the rubber cools during storage, the sulfur rapidly diffuses to the surface of the rubber compound and crystallizes, causing a ``bloom'' like appearance. This bloom would affect processing and performance properties, such as inter-ply adhesion.