Polyisobutene

Polyisobutene (CAS 9003-27-4), also known as polyisobutylene or PIB, is a synthetic hydrocarbon polymer produced by the polymerization of isobutylene. Across lubricant, sealant, and polymer processing industries, it functions as a viscosity modifier.

It acts as a plasticizer and tackifier depending on the specific molecular weight grade selected for the application. In lubricant and gear oil formulations, high-molecular-weight PIB acts as a viscosity index improver.

It serves as a base fluid component, extending film strength under load. Rubber compounders incorporate mid-range grades as a softening and processing aid, improving flexibility and reducing hardness in finished seals.

It is also used in gaskets and profiles. In automotive sealants and adhesives, PIB provides long-term tackiness and resistance to gas permeation, making it a preferred binder in various butyl-based formulations.

Low-molecular-weight grades are used as plasticizers in polyolefin blends, improving melt flow and surface finish in extruded and injection-molded parts. Polyisobutene is supplied as a viscous liquid or semi-solid.

Viscosity and molecular weight determine the commercial grade. Standard grades are differentiated by number-average molecular weight, typically ranging from low (300 to 1,000 Mn) to high (above 50,000 Mn).

Food-contact and pharmaceutical-grade PIB meeting FCC and USP specifications is available for applications requiring regulatory compliance. These grades ensure safety and quality for sensitive industrial uses.