Acrylonitrile-butadiene copolymer (CAS 9003-18-3), sold as NBR or nitrile rubber, is a fully polymerized butadiene-acrylonitrile elastomer. In normal solid commercial forms—bales, crumb, slab, sheet, pellets—it is not listed by name in the United Nations Model Regulations Dangerous Goods List in Part 3.2. The absence of a listing alone does not determine classification; the material must still be assessed against the criteria of Part 2. For solid NBR, that assessment does not lead to assignment to any hazard class: the polymer is not a flammable solid, not self-reactive, not oxidizing, not dangerous when wet, not toxic, not corrosive, and not environmentally hazardous under the aquatic toxicity criteria. This conclusion feeds directly into the modal regulatory instruments: ADR, RID, ADN, IMDG Code, and IATA DGR all treat the material as non-dangerous general cargo when it is offered in solid form.

Is NBR Subject to Any Hazard Class Under the UN Model Regulations?

No. The classification logic begins with the UN Model Regulations Part 2 criteria. A baled or pelletized NBR product does not satisfy the Class 4.1 flammable solid criteria described in the UN Manual of Tests and Criteria Part III, sub-section 33.2.1, because the consolidated mass does not show the rapid flame spread or burning rate required for that class. It is not pyrophoric and does not self-heat, so Class 4.2 does not apply. It contains no reactive metals or hydride structures, so Class 4.3 is not assigned. The polymer is not an oxidizing substance under Class 5.1. Solid NBR has negligible vapor pressure and no free liquid phase; therefore Class 3 is not relevant. It does not exhibit acute or chronic aquatic toxicity at the endpoint thresholds for Class 9 environmentally hazardous substances under Chapter 2.9.3, and it is not listed as a marine pollutant in the IMDG Code.

Nor does NBR fall within the Class 4.1 self-reactive or polymerizing substance category. It is a fully reacted elastomer; it does not undergo self-accelerating decomposition under transport conditions and does not require temperature-controlled stabilization. The absence of reactive initiators in the base copolymer distinguishes it from polymerizing monomer feedstocks.

The distinction between a non-dangerous polymer and its hazardous monomers is central. Acrylonitrile monomer is listed as UN 1093, Class 3, Packing Group I. 1,3-Butadiene is listed as UN 1010, Class 2.1. Once copolymerized into NBR, the polymer matrix is not equivalent to a mixture of free monomers. The transport assessment is based on the actual article or substance offered for carriage.

Under ADR 2025, the carriage of dangerous goods by road is triggered only when a substance appears in Table A of Chapter 3.2 or meets the criteria of Part 2. NBR solid has no entry in Table A and does not meet the criteria. Consequently, the consignment does not require a dangerous goods transport document under Chapter 5.4, placards under Chapter 5.3, or package marks and labels under Chapter 5.2. No tunnel restriction code or orange-coloured plate marking is required, and the appointment of a dangerous goods safety adviser under Chapter 1.8.3 is not triggered. The same argument applies under RID 2025 for rail and ADN 2025 for inland waterway dry cargo. In the United States domestic framework, 49 CFR 172.101 contains no Hazardous Materials Table entry for NBR, so no hazardous materials shipping papers, placards, or registration are required for the pure solid polymer.

IMDG Code Classification and Marine Pollutant Screening

For ocean freight, the governing instrument is the IMDG Code. Solid NBR is absent from the Dangerous Goods List in Chapter 3.2. The consignment is not assigned a UN number, packing group, EmS schedule, stowage category, or segregation group. The material is also not identified in the Code’s marine pollutant listings. Accordingly, no dangerous goods declaration is required under the IMDG documentation provisions, and the container need not display marine pollutant marks or class placards.

Environmentally hazardous classification is sometimes confused because acrylonitrile monomer is toxic to aquatic life. The solid polymer does not exhibit the same bioavailability: its high molecular weight and negligible water solubility limit dissolution and uptake. Published aquatic toxicity data for the solid polymer are limited. Unless a shipper possesses product-specific test data that demonstrate classification under Chapter 2.9.3, the solid copolymer is not classified as environmentally hazardous or as a marine pollutant.

The shipper still must comply with ordinary cargo requirements. Verified gross mass declarations under SOLAS VI/2 apply, and container stuffing should follow the IMO/ILO/UNECE CTU Code for load restraint, distribution, and packaging integrity. Wooden pallets and dunnage may be subject to ISPM 15 phytosanitary treatment. These are transport-safety and cargo-security obligations, not dangerous goods controls.

Dust Explosion Hazard Does Not Automatically Create a Transport Class

NBR dust generated by ambient grinding, cryogenic milling, or pneumatic transfer is a combustible particulate and may create an explosion risk in production and storage. That process-safety hazard is regulated under workplace and equipment regimes such as 2014/34/EU and 1999/92/EC, not by a transport hazard class unless the specific powder passes the relevant tests for Class 1 explosives or Class 4.1 flammable solids. A combustible dust alone is insufficient for transport classification. The UN Manual of Tests and Criteria prescribes specific burning-rate and propagation tests for flammable solids; typical NBR powder with coarse median particle size and low fines content does not default automatically into Class 4.1.

Published K_st and minimum ignition energy values for NBR-specific dust fractions are grade-dependent and not comprehensively tabulated in public transport classification sources. Shippers of finely divided NBR should have product-specific test data from a competent transport classification body before making a dangerous goods determination; otherwise the classification should be stated only for the solid form actually shipped.

The safety data sheet format prescribed by Commission Regulation (EU) 2020/878 amending REACH Annex II includes Section 14 transport information. For solid NBR, that section will normally state that the product is not classified as dangerous goods under ADR, RID, ADN, IMDG, and IATA DGR. The SDS remains the starting point, but Section 14 statements are supplier-specific and may describe only the pure solid polymer. A shipper must verify that the actual consignment—including any processing oil, carbon black masterbatch, silica, or other additives—has not altered the physical or toxicological profile. If the NBR is compounded, the assessment belongs to the prepared compound, not to the base copolymer.

Documentation for non-dangerous NBR therefore consists of ordinary commercial invoices, packing lists, and transport documents. The phrase “not restricted” is not required by dangerous goods regulations and should not be inserted into the dangerous goods declaration fields of a multimodal transport document. When an electronic shipping system requests a dangerous goods check, the entry should be completed as “non-dangerous” only after verifying the product form and packaging.

When Residual Acrylonitrile Monomer Content Shifts the Assessment

Commercial NBR grades contain bound acrylonitrile in the range of 18–50% by mass, but free residual acrylonitrile is a different parameter. In high-performance or low-free-monomer grades, residual acrylonitrile is controlled during polymerization and finishing; residual monomer does not exist as a free liquid phase. Under the mixture criteria in ADR 2.1.3.3 and 2.2.61.1.7, a trace monomer residue below the applicable cut-off cannot transmit the Class 3 or Class 6.1 classification of the parent monomer to the solid polymer. If free liquid monomer were present, or if the NBR were formulated as a solvent solution with a Class 3 solvent, classification would change.

Solvent-borne NBR cements and adhesives commonly contain ketones, esters, or aromatic hydrocarbon solvents. Those articles are classified separately, often as UN 1993 Flammable liquid, n.o.s., or by the specific solvent entry, depending on flash point and viscosity. An NBR latex may be water-based but can contain surfactants, biocides, or residual monomers that require assessment against aquatic toxicity criteria in Chapter 2.9.3. If the latex meets the criteria, it may be assigned UN 3082 Environmentally hazardous substance, liquid, n.o.s., or UN 3077 if shipped as a solid or paste. None of these secondary articles changes the classification of the solid copolymer itself.

Packaging for non-dangerous NBR follows commercial specifications rather than UN performance packaging. Production-scale finishing lines compress dried NBR crumb in hydraulic baling presses, then wrap the bales in low-melt polyethylene film. Bale masses commonly range from 25 kg to 1,400 kg depending on grade and downstream mixer configuration; palletized bales are stretch-wrapped for moisture protection. Because the consignment is not dangerous goods, no UN specification packaging marking is required. Packaging must nevertheless withstand normal handling, stacking, and storage; load-securing failures remain a general transport risk.

Operationally, NBR bales should be protected from prolonged exposure to direct sunlight and high ambient temperature. The polymer can soften and undergo cold-flow deformation under stack compression, particularly in tropical sea freight containers. High relative humidity does not create a dangerous goods condition, but moisture uptake may degrade surface appearance and promote marking issues. Shippers should verify clean, dry container interiors before loading and avoid co-stowage with heat-generating cargo or incompatible chemicals.

Air Freight Documentation Under IATA Dangerous Goods Regulations

Under the IATA DGR 66th ed., solid NBR is not listed in Section 4.2, List of Dangerous Goods. The consignment is accepted as general cargo. The Shipper’s Declaration for Dangerous Goods is not required, and the package must not bear hazard labels, UN specification marks, or dangerous goods handling labels solely on account of the NBR.

The air waybill should not state that the goods are dangerous when they are not. Some carriers apply their own general cargo acceptance procedures for rubber and polymer powders; those may include dust-tight packaging, minimum film thickness, or maximum package mass. Those operational limitations are carrier tariffs and cargo handling rules, not IATA DGR requirements.

If an NBR compound contains a hazardous plasticizer, blowing agent, or solvent, the compound may be a different article and must be classified on its own merits. For pure solid NBR, no dangerous goods approval, no pilot-in-command notification, and no dangerous goods training documentation are required under the air mode.