2,4'-MDI (Diphenylmethane-2,4'-Diisocyanate)CAS 5873-54-1
The minor structural isomer of MDI — typically a few percent of technical PMDI mixtures.
Toxic Chemical Databases
Substance-specific listings — these flags are for 2,4'-MDI alone, not for the broader family.
Chemical Type
Aromatic Diisocyanate — Asymmetric Isomer
Chemical Description
The 2,4'-isomer of MDI has one isocyanate group positioned ortho to the methylene bridge, giving it different reactivity than the symmetric 4,4'-isomer. Pure 2,4'-MDI is rarely used standalone but appears as a characterization marker for technical PMDI mixtures. Toxicologically it shares the MDI family's respiratory and skin sensitization profile.
Biological Activity
Severity scores specific to this substance, NOT the parent family average. Differences between siblings are real and meaningful.
Top Health Consequences
- Respiratory sensitization
- Skin sensitization
- Same MDI-family hazard envelope
Pathways of Exposure
- Inhalation during PMDI-based product application
- Dermal contact with technical mixtures
Building Materials with 2,4'-MDI
Listed alphabetically — product categories where this specific substance appears.
Specialty PU Adhesives
Technical PMDI Coating Mixtures
How We Keep 2,4'-MDI Out of a House
Avoiding 2,4'-MDI is only half of it. The replacement has to work in a mold free, airtight, PHPP-modeled assembly as well — and finding materials that do both is most of what we do.
If you want a house specified this way from the start, or an existing house assessed for what is already in it, that is the work we do. Earth Bound Homes builds in Atherton, Palo Alto, Redwood City and across the San Francisco Bay Area.