MDI [Methylene Bisphenyl Isocyanate

MDI [Methylene Bisphenyl Isocyanate] Characteristics
Synonyms Diphenyl methane 4,4’-diisocyanate
CAS No. 101-68-8
Chemical formula CH2(C6H4NCO)2
Vapour density ---
Safe Work Australia ES TWA 2 ppb (based on 0.02 mg/m3 as NCO)
STEL 7 ppb (based on 0.07 mg/m3 as NCO)
Flammable limits LEL --
UEL --
Chemical/physical properties MDI is one of a group of compounds known as aromatic diisocyanates. At room temperature, MDI is a white to yellow solid, liquefying at temperatures above 37 °C.
Hazardous properties Like most diisocyanates, exposure to MDI either by inhalation, ingestion or skin contact can lead to sensitisation(1). It is irritating to the skin (causing dermatitis) and eyes and can affect the respiratory system causing dyspnoea (breathing difficulty), pulmonary oedema and asthma.
Although it has very low volatility, the fact that it used in applications where heat can be generated and aerosols can be formed means that it can be inhaled.
Uses MDI is commonly used as a curing agent in for rigid polyurethane foams used for insulation and packaging applications. 
Detectors available Colorimetric paper tape (0 – 100 ppb)
Suggested alarm level(s) 5 ppb
Notes (1)  Sensitisation is a phenomenon occurring in some individuals, whereby exposure to a substance leads to those individuals having an increased sensitivity to the effects of that substance.


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