How Synthetic Rubber Is Made

Synthetic rubber production falls broadly into three parts: synthesis and purification of the monomer, the polymerisation process, and finishing of the rubber.

Purification

The basic raw material for synthetic rubber is the monomer. Common purification methods include distillation, washing and drying.

Polymerisation

Polymerisation is the reaction in which monomers form a polymer under the action of initiators and catalysts. Sometimes a single reactor is used; sometimes several are connected in series. Two processes dominate: emulsion polymerisation and solution polymerisation. Emulsion polymerisation is used for styrene-butadiene rubber, isoprene rubber, nitrile rubber and butyl rubber.

Finishing

Finishing takes the polymerised material — latex or cement — through removal of unreacted monomer, coagulation, dewatering, drying and packaging to give the finished rubber. Emulsion-polymerised latex is usually coagulated by adding electrolytes or polymeric coagulants to break the emulsion and precipitate the rubber crumb; solution-polymerised cement is mainly coagulated with hot water. The precipitated crumb carries a great deal of water and must be dewatered and dried.