Polyisobutene

Polyisobutene (CAS 9003-27-4), also known as polyisobutylene or PIB, is a synthetic hydrocarbon polymer produced by the polymerization of isobutylene.

Where is Polyisobutene used?

• Lubricants and gear oils: viscosity modifier and viscosity index improver for high-molecular-weight grades
• Sealants and adhesives: binder providing long-term tackiness and resistance to gas permeation in automotive and butyl-based formulations
• Rubber compounding: mid-range grades as softening and processing aid, improving flexibility and reducing hardness in finished seals
• Polyolefin blends: low-molecular-weight grades as plasticizers, improving melt flow and surface finish in extruded and injection-molded parts
• It serves as a base fluid component, extending film strength under load.
• Compatible with resins such as rosin esters and hydrocarbon resins.
• Used as an adhesion promoter in agricultural and pallet stretch films.
• Fully compatible with EPDM, SBS, SEBS, SBR, butyl rubber and polyisoprene.

Good to know: 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.

Formulation notes

• Made only from isobutylene monomers, whereas polybutene is made from a mixed C4 stream containing both isobutylene and n-butene units.
• Has poor low-temperature performance because its viscosity increases rapidly at low temperatures.
• High-reactivity PIB (HR-PIB) contains more reactive terminal vinylidene groups than conventional PIB and is suited to fuel and lubricant additive intermediates.

Typical specification

• PIB 32 offers fast migration and high final tack, making it suitable for stretch films.
• PIB 128 offers slower diffusion and longer processing time, making it suitable for rubber and plastic compounds.
• Glass transition temperature (Tg) of -60°C.
• Grades offered include PIB 4, 6, 10, 12, 24, 28, 30, 32 and 128.

Storage, packaging and handling

• Store in a cool place and protect from direct sunlight.
• No hazardous material transportation is required.

Frequently asked questions about Polyisobutene

How is polyisobutene incorporated into polymer systems?

It can be added to various polymers including polyethylene, polypropylene, and polystyrene.

Which low molecular weight grades are used in lubricants?

The low molecular weight grades used in lubricants are PIB1000, PIB1300 and PIB2400.

What is the role of polyisobutene in lubricant oil additives?

In lubricant oil additives, it is used mainly as a raw material for producing dispersants.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.