Skip to content
CarCareTruth

Polyisobutene

  • Polymers
  • CAS 9003-27-4
  • IUPAC: Poly(1-methylethylene)

Polyisobutene (CAS 9003-27-4) appears in 2 of the 2,122 car-care products CarCareTruth tracks (as of August 2026).

Not classified as hazardous under GHS. A synthetic polymer with no known toxicity in normal use. Low-molecular-weight grades are slightly more mobile than high-MW grades but neither bioaccumulates.

Polyisobutene (PIB) is a synthetic hydrocarbon polymer derived from isobutylene. It is widely used in cosmetics, food packaging adhesives, and leather conditioners as a film-forming and waterproofing agent. At the concentrations found in leather care products (typically 50–70%), it forms a flexible, breathable barrier on the leather surface that resists water penetration without creating a greasy film.

Polyisobutene is not classified as hazardous under GHS/OSHA HazCom. It has no skin sensitization, irritation, or inhalation hazard classification. It does not biodegrade readily, making it an environmentally persistent ingredient, but its low aquatic toxicity and non-volatile nature limit environmental exposure risk in leave-on applications.

Health & environment profile

VOC
no
Prop 65 listed
no
Asthmagen
no
EPA Safer Choice
no
Aquatic toxicity
no
Biodegradable
no
Bioaccumulative
no
Persistent
yes
Ozone depleting
no
Microplastic
no
PFAS
no
Env. score
3/5
Purpose: Film-forming conditioning agent and protective barrier in leather care products

Common questions about Polyisobutene

What is Polyisobutene used for in car care?
Film-forming conditioning agent and protective barrier in leather care products
Is Polyisobutene a VOC?
No. Polyisobutene is not classified as a volatile organic compound (VOC).
Is Polyisobutene on California's Proposition 65 list?
No. Polyisobutene is not on California's Proposition 65 list.

2 products contain this

Related

Health and environment notes translate the manufacturer Safety Data Sheet, the GHS classification, and authoritative regulatory listings (California Prop 65, EPA). Not medical advice. They describe the ingredient itself; whether a hazard applies to a finished product depends on its concentration and how it's used.