Terminology

• PUR / PIR: polyurethane / polyisocyanurate (PIR boardstock insulation)
• TDI / MDI: aromatic diisocyanates; HDI, IPDI, H12MDI are aliphatic, used where color stability matters
• Polyol: polyether or polyester alcohol reacted with the isocyanate
• Urethane (carbamate) link: the bond joining the units
• Blowing agent: gas source for foam cells (CO2, pentane, or HFCs after the early 1990s)
• Closed-cell / open-cell: foam cell structures for rigid insulation / cushions

History and demand

Invention

• 1937: Otto Bayer and coworkers at IG Farben, Leverkusen, first made polyurethanes
• 1952: polyisocyanates commercially available; 1954: flexible foam production began; 1956 to 1957: polyether glycols introduced by DuPont, BASF, and Dow

First uses in construction

• Rigid foams became high-performance insulation after chlorofluoroalkane blowing agents, cheaper polyether polyols, and MDI became available; the Montreal Protocol moved blowing agents to CO2, pentane, and HFCs by the late 1990s

Sourcing

• China holds about 45 percent of global MDI and TDI capacity (industry analysis); Wanhua Chemical is the largest TDI producer at 1.47 million tonnes a year by the end of 2025

Demand trend

• Global production about 25 million tonnes in 2019, roughly 6 percent of all polymers; foams were 67 percent of production in 2016
• Research into bio-derived polyols and isocyanate-free polyhydroxyurethanes is under way

Composition and production

Raw materials

• Diisocyanate (or polymeric isocyanate) plus polyol; higher molecular weight polyols give flexible products, lower molecular weight give rigid ones
• Chain extenders, crosslinkers, catalysts, and surfactants adjust processing and properties

Product forms

• Flexible and rigid foams, coatings, adhesives, sealants, electrical potting compounds, elastomers, and fibers

Properties

Thermal and moisture

• Closed-cell rigid foams serve as thermal insulation

Fire behavior

• Combustible; fires can release carbon monoxide, hydrogen cyanide, nitrogen oxides, and isocyanates
• Flame retardants are typically added, especially for furniture; almost all are considered harmful

Uses in buildings

Building elements

• Resinous Flooring: aliphatic urethane topcoats with UV stability and abrasion resistance
• Wall and Roof Insulation: rigid foam boards, polyisocyanurate boardstock, and spray foam
• Sealants and Flashing: sealants and gaskets

Pros and cons

Pros

• Closed-cell rigid foam is a thermal insulation
• Wide range of forms from soft foam to elastomers
• Aliphatic isocyanates keep color stable in coatings

Cons

• Combustible, with toxic combustion products
• Isocyanates are skin and respiratory sensitizers
• Flame retardants raise health concerns

Sustainability

Health

• Isocyanates are skin and respiratory sensitizers (OSHA); amines, glycols, and phosphates in spray foams also pose risks
• Fully reacted polyurethane is not regulated by OSHA for carcinogenicity

Manufacturing and cost

Main manufacturers and suppliers

• BASF
• Dow
• Covestro
• Huntsman

Trade association: American Chemistry Council.

Sources

• Wikipedia: Polyurethane, https://en.wikipedia.org/wiki/Polyurethane
• UpCodes: 2024 IBC Chapter 26 plastic, https://up.codes/viewer/department-of-defense/ibc-2024/chapter/26/plastic
• Wikimedia Commons: Backfill of polyurethane foam.jpg, photo by Hmshare (CC BY-SA 4.0), https://commons.wikimedia.org/wiki/File:Backfill_of_polyurethane_foam.jpg
• Faxiang Gongchang: China MDI and polyurethane, 2025 global capacity, https://faxiangongchang.com/en/reports/china-mdi-polyurethane-2026