Description:
Toluene diisocyanate (TDI), (OCN)2C6H3CH3, is a water-white to pale-yellow liquid with a sharp, pungent odor. It reacts with water to release carbon dioxide. The specific gravity is 1.22, which is heavier than water. TDI is toxic by inhalation and ingestion, and is a strong irritant to skin and other tissue, particularly the eyes. The TLV is 0.005 ppm in air, and the IDLH is 10 ppm. The target organs are the respiratory system and the skin. The four-digit UN identification number is 2078. The NFPA 704 designation is health 3, flammability 1, and reactivity 3. The white section at the bottom of the diamond has a W with a slash through it, indicating water reactivity. The primary uses of TDI are in the manufacture of polyurethane foams, elastomers, and coatings.
Key Features:
Molecular Formula ：C9H6N2O2
Molecular Weight：174.16
Melting Point：20 - 21 °C
Boiling Point：251 °C
Flash Point：270 °F / 132 °C (cc)
Carcinogenicity:
Acute toxicity. Industrial experience has demonstrated that acute exposure to TDI vapors can produce severe irritant effects on mucous membranes, the respiratory tract, and the eyes. An acute attack of an asthma-like syndrome may occur. Exposure to high concentrations may lead to chemical bronchitis with severe bronchospasm, chemical pneumonitis, pulmonary edema, headache, and insomnia.With sufficient exposure, all persons would appear to experience these effects even on their first exposure.
Chronic and subchronic toxicity. Repeated exposures at lower concentrations of TDI may produce a chronic-like syndrome in many people. Symptoms may include coughing, wheezing, tightness or congestion in the chest, and shortness of breath and appear to be related to hypersensitization. Interstitial pulmonary fibrosis does not occur from moderately elevated exposures to TDI (mean 0.07, peak 0.2 ppm).
Exposure to TDI may lead to immunological sensitization. Some individuals become sensitized on first exposure; others may develop symptoms after exposure over days, months, or years. Other workers have experienced only minimal or no respiratory symptoms for several months of low level exposure, then suddenly develop acute asthmatic reactions to the same level. The nature of the sensitization process is unknown, and many authors have referred to it as an “allergy;” the respiratory response in sensitized people is referred to as true asthma, comparable to asthma excited by pollens and other exoallergens. Some TDI-sensitized people, however, have no history of prior allergic disease.
Storage:
Work with TDI should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact.
