Butyl Rubber, sometime just called “butyl”, is a synthetic rubber, a copolymer of isobutylene with isoprene. The abbreviation IIR stands for isobutylene isoprene rubber. Polyisobutylene, also known as “PIB” or polyisobutylene, (C4H8)n, is the homopolymer of isobutylene, or 2-methyl-1-propene, on which butyl rubber is based. Butyl rubber is produced by polymerization of about 98% isobutylene with about 2% isoprene. Structurally, polyisobutylene resembles polypropylene, but has two methyl groups substituted on every other carbon atom, rather than one. Polyisobutylene is a colorless to light yellow viscoelastic material. It is generally odorless and tasteless, though it may exhibit a slight characteristic odor.

Gomec butyl tape is a high-adhesive butyl sealing tape protected by a reinforced aluminum film. The aluminum film gives the product resistance to ageing, oxidizing and to the aggression of chemical and atmospheric agents. Butyl tape is self-fusing butyl rubber mastic coated with aluminum laminate; the adhesive face of the butyl is protected by a siliconized and peelable liner, ideal for making water and moisture-resistant seals. Gomec butyl tape is a high-tack sealant tape with excellent adhesion to metal. It is widely used in Roofing and insulating materials, metal facades, air ducts, roofs and terraces, in places such as chimney-roof assemblies, roof vents, etc. to protect against water and moisture.