Pipewrap adhesive

Butyl rubber is a copolymer of isobutylene with a minor amount of isoprene (0.8-2 mole %). Unlike PIB, butyl can be crosslinked to improve the otherwise poor cohesive properties of this class of adhesive. The major use for BR is in anticorrosion wrap for gas nd oil transmission pipes. The backing for this tape consists of a thick polyethylene or PVC film, loaded with carbon black. The adhesive mass, which is quite thick (up to 12 mils) not only contains the usual tackifiers, of which many can be used, but also a high concentration of particulate filler. This tape lends itself favorably to calendar manufacture. A typical formulation for a pipewrap adhesive is given in Table 6. 

Table 6. Typical Formulation for Calenderable Pipewrap Adhesive.

Corrosion Protection. Although steel underground transmission lines are often protected by coal tar or fusion bonded epoxy coatings, a large volume of polyethylene tapes as well as some vinyl-backed tapes are used for corrosion protection. Pipes of large diameter, such as oil line pipes, are usually machine-wrapped in the field just prior to placement in the ground. The tapes are unusual in that the backing is from 12 to 15 mils thick and the butyl-based adhesive is approximately of the same thickness. For the pipeline industry the rolls are 18 in. wide and contain up to 800 feet of tape. There is a reduction currently in domestic pipeline construction but appreciable amounts of pipewrap are exported. 

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See also in sourсe #XX -- [ ]

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