Table 1.
Selected physicochemical properties of commercially important isocyanates.
| Isocyanatea | MW (g/mol) | VP (mm Hg)b | Volatilityc | 1 ppm = x mg/m3 |
|---|---|---|---|---|
| HDI | 168.2 | 0.02 | Very high | 6.88 |
| TDI | 174.2 | 0.02 | Very high | 7.13 |
| IPDI | 222.3 | 0.0003 | Moderate | 9.09 |
| MDI | 250.3 | 0.000005 | Very low | 10.24 |
VP, vapor pressure.
a
All isocyanates are liquids at room temperature, except for MDI.
b
VP at 20°C, except for MDI (25°C); data from Streicher et al. (1994).
c
The higher the volatility, the shorter the residence time of isocyanates on the skin; most polymeric isocyanates (MW ~ 500) are nonvolatile at room temperature.