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Monomers, Polymers, and Plastics
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
Butyl rubber is a copolymer of isobutylene (97.5%) and isoprene (2.5%). The polymerization is carried out at low temperature (below −95°C, <139°F) using aluminum chloride (AlCl3) co-catalyzed with a small amount of water. The co-catalyst furnishes the protons needed for the cationic polymerization: AlCl3+H2O→H+(AlCl3OH)−
Polymer Technology
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Over 5.5 billion pounds of synthetic rubber is produced annually in the United States. The principal elastomer is the copolymer of butadiene (75%) and styrene (25) (SBR) produced at an annual rate of over 1 million tons by the emulsion polymerization of butadiene and styrene. The copolymer of butadiene and acrylonitrile (Buna-H, NBR) is also produced by the emulsion process at an annual rate of about 200 million pounds. Likewise, neoprene is produced by the emulsion polymerization of chloroprene at an annual rate of over 125,000 tons. Butyl rubber is produced by the low-temperature cationic copolymerization of isobutylene (90%) and isoprene (10%) at an annual rate of about 150,000 tons. Polybutadiene, polyisoprene, and ethylene–propylene copolymer rubber (EPDM) are produced by the anionic polymerization of about 600,000, 100,000, and 350,000 tons, respectively. This encompasses only some of the many elastomers produced.
Elastomeric Polymers
Published in Kathleen Hess-Kosa, Building Materials, 2017
Butyl rubber, a thermoset elastomer, comprises of 98% polyisobutylene and 2% isoprene. See Figure 7.1. Although the terms butyl rubber and polyisobutylene are often used interchangeably, polyisobutylene is not a rubber—without isoprene (which provides for crosslinking during vulcanization). The polyisobutylene monomer is isobutylene, and the polymerization process is a high-energy exothermic process. Thus, polymerization requires extreme cold (e.g., −100°C) to control the reaction rate. In construction, butyl rubber is used as rubber sealing tape, caulk, and as a recycled rubber “additive” in roofing asphalt.
A brief review of sealants for cement concrete pavement joints and cracks
Published in Road Materials and Pavement Design, 2021
Lu Lu, Deying Zhao, Jizhou Fan, Guoqiang Li
In addition to bitumen or coal-tar based sealants, polymeric sealants have played a major role over the years. The earliest polymeric sealants were triglyceride esters of long-chain fatty acids. They were considered as low-performance sealants and showed little or no chemical curing after application. They were inexpensive, had little flexibility, and tended to crack when they were subjected to moderate joint movement. Solvent-based acrylics and butyl sealants are considered medium performance sealants. Butyl rubber is prepared by the polymerisation of isobutylene. Butyl sealants are relatively low in price and adhere to a wide range of substrates. Solvent-based butyl sealant shows joint shrinkage due to solvent loss and sealant stringiness during application.