Study On The Emission Of Toluenediisocyanate From Paints

Indoor decorating and refurnishing materials can release poisonous and harmful substances,so they beautify indoor environment, meanwhile, pollute it. Toluenediisocyanate (TDI) is a major isocyanate compound used commercially in polyurethane foams, painting, adhesives and elastomers belonging to semi-volatile organic compound. It is now very popular in our life, and you can find it in the mattess and sofa. Because paints are used widely ,they have become the second pollutant source in the modern society. In our country, polyurethane coatings mostly are aromatic solvent-based coatings, and usually use toluenediisocyanate. The major toxicities of TDI are sensitization and stimulation, if long-time exposure to TDI is associated with hypersensitivity pneumonitis, contact dermatitis and even carcinogenesis.Now , more and more countries are paying attention to the harmfulness of TDI, and have suggested control standards. Many researchers have studied on the emission of TVOCs, but never on TDI. As TDI is an active and unsteady compound, they need to be derivatised during the sampling step in previous Documentations. This paper studies the emission of TDI using small environmental test chamber, and the effect of temperure, relative humidity and air exchange rate on the emission.The major content and the major viewpoint of this paper as follows:1. Choose sampling method: sampling by Tenax-TA/thermal desorption reqires strict conditions about the experiment because of the instability of TDI. So choose hydrochloride and acetic acid mixture as the absorption liquid to absorb TDI in the small environmental test chamber,and the result is stable.2. The process of treating the absorption liquid: Treat the absorption liquid by derivative method ,determine C8F14O3 as the best derivatizing agent, 30min as the time of derivation, and the amount of derivatizing agent is 20μL, then optimize instrument condition of GC/MS to reach a higher sensitivity than GC.3. At different temperatures(18℃,23℃,30℃) of the small environmental test chamber study the emission of TDI. The results show that the temperature has great effect on the emission of TDI. When the temperature increases, the emission rate of TDI speeds up, and the concentration of TDI increases. The attenuation equation and half life at different temperatures respectively are y=2.1349e^-0.0846, 8.19h; y=58.004e^-0.1148x ,6.04h; y=73.38e^-0.1566x,4.42h, so its concentration decay quickly with temperature.4. At different relative humidity (45%, 55%, 70%)of the small environmental test chamber study the emission of TDI. It is found that when the relative humidity increases, the emission rate of TDI speeds up, but its concentration decays quickly. The attenuation equation and half life at different relative humidities respectively are y=58.004e^-0.1148x ,6.04h;y=12.693e^-0.129x,5.36h;y=10.34e^-0.190x,3.65h.5. Set different air exchange rates(0.8m³/h, 1m³/h, 1.2m³/h)of the small environmental test chamber then study the emission of TDI.. We found that when the air exchange rate increases, the emission rate of TDI speeds up, but its concentration decreases and decays quickly. The attenuation equation and half life at different air exchange rates respectively are y=48.499e^-0.103x, 6.73 h;y=58.004e^-0.1148x,6.04h;y=9.7429e^-0.137x,5.06h.6. Study on the experiment model of TDI releasing from paints, and found that the emission of TDI basically corresponds"VB+Power"model.7. Innovative point of this paper lies in that study on the emission of TDI-single compound from paint for the first time, and improve the analysis method for TDI.