UN/NA Number Reference
DOT Class 6.1 Toxic Substance placard

UN 2281: Hexamethylene diisocyanate

49 CFR 172.101 Hazardous Materials Table·ERG 2024

DOT Classification and Shipping

UN 2281 is assigned the proper shipping name Hexamethylene diisocyanate in the U.S. DOT Hazardous Materials Table (49 CFR 172.101). It is classified as a Class 6.1 Toxic Substance material, Packing Group II. Required label(s): 6.1.

Packing group indicates the degree of danger within a hazard class: PG I is high danger, PG II medium, PG III low. The proper shipping name, hazard class, UN number, and packing group together form the basic shipping description that must appear on shipping papers and, where required, on the package and placard.

Emergency Response (ERG Guide 156)

Hazards: TOXIC or CORROSIVE. FLAMMABLE. Vapors may travel to ignition source.

Fire: Alcohol-resistant foam, dry chemical, CO2. Water spray for cooling only.

Spill: Eliminate ignition sources. Do not touch. Ventilate area.

Chemical and Physical Properties

Hexamethylene diisocyanate appears as a colorless crystalline solid. Toxic by ingestion and is strongly irritating to skin and eyes. It is used to make nylon.

CAS Number: 822-06-0
Molecular Formula: C8H12N2O2
Molecular Weight: 168.19 g/mol
Color / Form: Liquid
Odor: Sharp, pungent odor
Boiling Point: 491 F
Melting Point: -67 °F (NTP, 1992)
Flash Point: 284 F
Autoignition: 454 °C
Specific Gravity: 1.0528 (sinks in water)
Vapor Pressure: 0.05 mmHg at 75 F
Vapor Density: 5.81 (heavier than air)
Water Solubility: Reacts with water
Log P: 1.08

Regulatory Data

CERCLA RQ (40 CFR 302.4)
100 lb
OSHA PEL
none
NIOSH REL
TWA 0.005 ppm (0.035 mg/m 3 ) C 0.020 ppm (0.140 mg/m 3 ) [10-minute]
IDLH
N

A release of this material at or above its CERCLA reportable quantity (100 lb) requires immediate notification to the National Response Center at 800-424-8802.

Special Provisions

49 CFR 172.102 special provision codes for this entry: IB2, T7, TP2, TP13. These codes modify the general requirements (packaging, quantity limits, exceptions) for this specific material. Look up each code in 49 CFR 172.102 for the full text.

Need the full interactive record? Open UN 2281 in the SpillNerd lookup tool for the live database entry with placard graphics, GHS pictograms, full segregation tables, and synonym search. For another material, use the UN number and chemical lookup.

Reference data compiled from the DOT Hazardous Materials Table (49 CFR 172.101), the 2024 Emergency Response Guidebook, and public chemical databases (PubChem, NIOSH, EPA). Always verify the correct shipping description against the current regulation and the manufacturer's SDS Section 14 before shipping.