Polymeric MDI (PMDI)CAS 9016-87-9
The workhorse of spray polyurethane foam — a low-volatility oligomer mix dominated by 4,4'-MDI.
Toxic Chemical Databases
Substance-specific listings — these flags are for Polymeric MDI alone, not for the broader family.
Chemical Type
Polymeric Aromatic Diisocyanate Mixture
Chemical Description
PMDI is a technical mixture of monomeric MDI plus higher oligomers — typically 30-50% 4,4'-MDI by weight, with the balance being 3-ring, 4-ring, and higher PMDI species. The mixture is the form actually shipped to spray-foam contractors. Lower vapor pressure than pure MDI reduces vapor-phase exposure but aerosolized spray droplets still expose the lung directly. The respiratory sensitization endpoint is identical to pure MDI.
Biological Activity
Severity scores specific to this substance, NOT the parent family average. Differences between siblings are real and meaningful.
Top Health Consequences
- Occupational asthma from spray aerosol exposure
- Respiratory sensitization — lifelong once triggered
- Skin sensitization and contact dermatitis
- Off-gassing risk concentrated during cure window
Pathways of Exposure
- Inhalation of aerosolized PMDI droplets during spray foam install
- Off-gassing during the cure phase (first 24-72 hours after application)
- Re-aerosolization from sanding, cutting, or thermal abuse
Building Materials with Polymeric MDI
Listed alphabetically — product categories where this specific substance appears.
Engineered Wood Adhesives (PMDI-Bonded OSB/MDF)
Polyurethane Spray Foam Insulation
Structural Insulated Panel Cores