HS Code for Polyisobutylene

Polyisobutylene (PIB) is classified under HS code 3902.20. This classification falls within Chapter 39 (Plastics and articles thereof) and heading 3902, which covers polymers of propylene or of other olefins in primary forms. Polyisobutylene is a synthetic hydrocarbon polymer produced by the polymerization of isobutylene. The term "primary forms" is strictly defined in Note 6 to Chapter 39 and includes liquids, pastes, dispersions, solutions, and blocks of irregular shape, granules, or powders. PIB is widely used in the production of adhesives, sealants, and as an additive in fuels and lubricants. Because it is a polymer of an olefin (isobutylene) and is typically traded in bulk liquid or semi-solid forms, it is specifically assigned to the 3902.20 subheading. The classification remains consistent regardless of the molecular weight, provided it remains a homopolymer of isobutylene.

Products Included

• Liquid polyisobutylene (low molecular weight)
• Semi-solid PIB resins
• PIB used as a viscosity index improver
• Polyisobutylene in primary blocks or lumps
• High molecular weight PIB for adhesive bases

Common Misclassification

Polyisobutylene is often confused with HS code 4002.31 or 4002.39, which cover halo-isobutene-isoprene rubber (CIIR or BIIR) and butyl rubber (IIR). While PIB is chemically related to butyl rubber, Chapter 40 is reserved for synthetic rubber that can be vulcanized. Pure polyisobutylene cannot be vulcanized in the same manner as butyl rubber and therefore must stay in Chapter 39. Another misclassification occurs in 3811.21, where PIB-based lubricant additives are sometimes placed; however, pure PIB in primary form belongs in 3902.20.

FAQ

What is the HS code for polyisobutylene?

The HS code for polyisobutylene in primary forms is 3902.20.

Is polyisobutylene classified as a rubber?

No, polyisobutylene is classified as a plastic under 3902.20, whereas butyl rubber (a copolymer) is classified under 4002.