Product classification
HS code for IIR rubber: 4002.31
Rubber, synthetic, isobutene-isoprene (butyl) rubber (IIR), in primary forms or in plates, sheets or strip.
Classification of IIR rubber under HS 4002.31
IIR rubber, or isobutene-isoprene rubber, is classified under HS code 4002.31. This classification is based on the chemical structure of the synthetic polymer. Chapter 40 of the Harmonized System covers rubber and articles thereof, with heading 4002 specifically addressing synthetic rubber and factice derived from oils. The sub-heading 4002.31 is dedicated to isobutene-isoprene (butyl) rubber in its primary forms, such as bales, blocks, or crumbs, or in unvulcanized plates, sheets, and strips. Butyl rubber is valued for its exceptional impermeability to gases and its high chemical resistance. The classification process requires identifying the monomer composition; for a product to fall under this code, it must meet the technical definition of synthetic rubber as provided in the Chapter 40 notes, which involves the ability to be cross-linked and undergo elastic recovery.
- Covers
- Standard butyl rubber (IIR) in bales
- Unvulcanized IIR sheets for industrial lining
- IIR crumbs for adhesive manufacturing
- Butyl rubber masterbatches in primary forms
- IIR strips for sealant production
- Also under 4002.31
- ExxonMobil Butyl
- Lanxess Butyl
- Arlanxeo Butyl
- Bicycle inner tubes
- Pharmaceutical vial stoppers
Codes often confused with 4002.31
Common mistake. IIR rubber is often confused with halo-isobutene-isoprene rubber (CIIR or BIIR), which is classified under HS code 4002.39. While both are butyl rubbers, the halogenated versions contain chlorine or bromine to improve vulcanization speed. Additionally, importers sometimes mistakenly use 4001.10, which is reserved for natural rubber latex, or 4002.11, which covers Styrene-butadiene rubber (SBR). Accurate classification depends on the specific chemical modification of the isobutene-isoprene chain.
Top exporters and importers of HS 400231 (the code used for IIR rubber), 2025
In 2025, the largest exporter of HS 400231 (the code used for IIR rubber) in UN Comtrade data was Russia, with about 30% of world exports; the largest importer in UN Comtrade data was China, with 40% of world imports. Countries that did not report 2025 data are estimated from partner records, which can understate them.
Figures cover everything classified under HS 400231, not only IIR rubber.
Top exporters 2025 · share of world exports
- 1 Russia* ~$203M 30% of world exports · partner records ↗
- 2 Saudi Arabia $128M 19% of world exports
- 3 China $80M 12% of world exports
World total: $669M Reported figures on UN Comtrade ↗
Top importers 2025 · share of world imports
- 1 China $249M 40% of world imports
- 2 Thailand $53M 8.5% of world imports
- 3 India $34M 5.5% of world imports
World total: $624M Reported figures on UN Comtrade ↗
How these figures are built
109 countries reported 2025 trade to UN Comtrade in HS 2022, and their own totals are used. Countries marked * did not, so their figures add up what other countries recorded trading with them, and their exports are valued at buyers' CIF prices. Those estimates miss trade with other non-reporting countries, so they can be low, and a non-reporting country can rank higher than shown or be missing from the list. World totals add both and leave out trade between two non-reporting countries. Figures are in current US dollars; reported imports are mostly valued CIF and exports FOB, and exports include re-exports. The UN Comtrade links show the underlying records; they can also list a few reporters left out here (regional groups and older HS editions).
Source: UN Comtrade (United Nations Statistics Division), 2025 annual data.
Brazil NCM code for IIR rubber
Brazil classifies IIR rubber under NCM 4002.31.00: HS 4002.31 with 00 added.
Source: Siscomex NCM table, updated Oct 2026. The Portuguese text on each NCM page is the official one.
Questions about IIR rubber
What is the HS code for IIR rubber?
The HS code for IIR rubber is 400231 (Rubber; synthetic, isobutene-isoprene (butyl) rubber (IIR), in primary forms or in plates, sheets or strip). The HS code for IIR (isobutene-isoprene) rubber in primary forms or sheets is 4002.31.
How do I classify IIR rubber for customs?
IIR rubber is classified under HS code 400231 — Rubber; synthetic, isobutene-isoprene (butyl) rubber (IIR), in primary forms or in plates, sheets or strip. This is a 6-digit subheading level code.
Does this code include finished inner tubes?
No, finished inner tubes made from IIR rubber are classified under heading 4013. HS code 4002.31 only applies to the raw material or unvulcanized intermediate forms.
Which countries are the top exporters of IIR rubber (HS 400231)?
In 2025, the top exporters of HS 400231 (the code used for IIR rubber) in UN Comtrade data were Russia (about $203M, 30% of world exports), Saudi Arabia ($128M) and China ($80M). World exports came to about $669M, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.
Which countries are the top importers of IIR rubber (HS 400231)?
In 2025, the top importers of HS 400231 (the code used for IIR rubber) in UN Comtrade data were China ($249M, 40% of world imports), Thailand ($53M) and India ($34M). World imports came to about $624M, adding countries' reported figures and partner-based estimates for those that did not report (UN Comtrade data). Countries that did not report 2025 data are estimated from partner records, which can understate them.
Is the HS code for IIR rubber the same in all countries?
The base HS code 400231 for IIR rubber is internationally standardized for the first 6 digits across 200+ countries. Individual countries may add additional digits for national tariff lines and specific classifications.
What is the NCM code for IIR rubber in Brazil?
In Brazil, IIR rubber (HS 400231) is classified under NCM 4002.31.00.