Hydrolytic Stability of Toluene Diisocyanate and Polymeric Methylenediphenyl Diisocyanate Based Polyureas under Environmental Conditions
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- 作者：Vahid Sendijarevic ; Aisa Sendijarevic ; Ibrahim Sendijarevic ; Robert E. Bailey ; Denis Pemberton ; and Kurt A. Reimann
- 刊名：Environmental Science & Technology
- 出版年：2004
- 出版时间：February 15, 2004
- 年：2004
- 卷：38
- 期：4
- 页码：1066 - 1072
- 全文大小：125K
- 年卷期：v.38,no.4(February 15, 2004)
- ISSN：1520-5851
文摘
Polyureas were prepared by reacting toluene diisocyanate(TDI) or polymeric methylenediphenyl diisocyanate(PMDI) with water under prolonged vigorous mixing atroom temperature. Hydrolytic degradation of these (powdered)TDI- and PMDI-based polyureas was studied by measuringthe rates of formation of free toluenediamine (TDA) ormethylenedianiline (MDA) in water as a function of timeby utilizing HPLC. The heterogeneous hydrolysis reactionswere carried out in glass reaction tubes under nitrogenwith initial polyurea loadings of 2 g/L in deionized water orbuffer solution. In the case of TDI-polyurea, concentrationsof free 2,4- and 2,6-toluenediamine in water weremeasured after hydrolysis at 120, 140, and 160 
C. Thehydrolysis of PMDI-polyurea was carried out at 150, 160,and 170 C, and concentrations of 2,4'-methylenedianiline (2,4'-MDA), 4,4'-methylenedianiline (4,4'-MDA), and 2,4-bis(p-aminobenzyl)aniline were measured. In both cases the rateof formation of diamine was well represented by both apseudo-first-order reaction and a zero-order reaction. Thetemperature dependence of rate constants fit Arrheniusbehavior. The half-time for hydrolysis of TDI-polyurea at 25C was calculated to range from about 18 000 to 300 000years and that of PMDI-polyurea was estimated to rangefrom about 110 000 to 12 million years, depending on thekinetic assumptions made. The half-times for hydrolysis atbuffered pH levels of 4, 7, and 9 were within a factor of2 of those in deionized water. These results are of importancein understanding the fate of polyureas formed in theevent of a release of TDI or PMDI into the environment.
C. Thehydrolysis of PMDI-polyurea was carried out at 150, 160,and 170 C, and concentrations of 2,4'-methylenedianiline (2,4'-MDA), 4,4'-methylenedianiline (4,4'-MDA), and 2,4-bis(p-aminobenzyl)aniline were measured. In both cases the rateof formation of diamine was well represented by both apseudo-first-order reaction and a zero-order reaction. Thetemperature dependence of rate constants fit Arrheniusbehavior. The half-time for hydrolysis of TDI-polyurea at 25C was calculated to range from about 18 000 to 300 000years and that of PMDI-polyurea was estimated to rangefrom about 110 000 to 12 million years, depending on thekinetic assumptions made. The half-times for hydrolysis atbuffered pH levels of 4, 7, and 9 were within a factor of2 of those in deionized water. These results are of importancein understanding the fate of polyureas formed in theevent of a release of TDI or PMDI into the environment.