Polybutene and polyisobutylene are hydrocarbon rubber-based sealants that are characterized by high elongation. However, they are susceptible to:
attack by ozone.
Polyisobutylene is a permanently tacky sealant and as such has a self-healing characteristic. It is a glass-clear polymer with good elastomeric properties. Polyisobutylene has much greater cold flow than most other elastomers. Low viscosity grades are used in applications that require a high degree of flow on applications such as insulated glass and the potting of electrical connectors.
These sealants are generally available as solvent release systems, preformed tapes, and hot melt applied sealants. They are also used as plasticizing agents for oleoresinous caulks and certain elastomeric sealants. Commercial sealants contain:
fillers such as carbon black, zinc oxide or silica
tackifiers, such as rosins
solvents such as cyclohexane.
Polyisobutylene is often used as an additive for other sealants or tapes, primarily butyl tape.