Toluene Diisocyanate TDI

The laser flash photolysis of aromatic diisocyanate based polyurethanes in solution provides evidence for a dual mechanism for photodegradation. One of the processes, an N-C bond cleavage, is common to both TDI (toluene diisocyanate) and MDI (methylene 4,4 -diphenyldiisocyanate) based polyurethanes. The second process, exclusive to MDI based polyurethanes, involves formation of a substituted diphenylmethyl radical. The diphenylmethyl radical, which readily reacts with oxygen, is generated either by direct excitation (248 nm) or indirectly by reaction with a tert-butoxy radical produced upon excitation of tert-butyl peroxide at 351 nm. 

Two final examples of the sensitivity and general applicability of the FTIR gas analysis technique are illustrated in Fig. 8. Trace (A) shows the spectrum obtained from an ultra-air filled 70 liter sampling bag into which had been injected, 18 hours previously, 4.8 microliters of TDI, toluene diisocyanate. On the basis of the single feature at 2273 cm l, it is estimated that 50 ppb TDI could be detected. The lower Trace (B), shows the spectrum of nickel carbonyl. This highly toxic but unstable gas was found to decay rapidly at ppm concentrations in ultra air (50% lifetime 15 minutes). Calibration of its spectrum was established by recording successive spectra at ten minute intervals and by attributing the increase in carbon monoxide concentration (calibration known) to an equivalent but four times slower decrease in nickel carbonyl concentration. The spectrum shown represents 0.6 ppm of the material. Note the extraordinary absorption strength. The detection limit is thus less than 10 ppb. 

Toluene Diisocyanate (TDI) Toluene diisocyanates (2,4- and 2,6 isomers) are produced from toluene diamine derived from dinitrotoluene, which is produced by the nitration of toluene with nitric/sulfuric acid mixtures. TDI is used to make flexible polyurethane foams, elastomers and coatings. 

TDI = toluene diisocyanate 342 TEDFO = b is-(trin itroethy I )-d ifl uo r-formal... 

The polyisocyanates which can be used for preparing isocyanate-based foams are mainly aromatic compounds and some aliphatic or aralkyl polyisocyanates. TDI (toluene diisocyanate) is widely used for flexible foams. Pure MDI (diphenylmethane diisocyanate) is used for elastomers and coatings. Modified TDI and modified MDI are used for high-resilience flexible foams. Polymeric isocyanates (polymeric MDI or oligomeric MDI) are mostly used for preparing rigid urethane and isocyanurate foams, and in part, for preparing flexible and semi-flexible foams. 

Table 3 Important Polyisocyanates TDI Toluene diisocyanate (Tolylene d1Isocyanate)...

ABS, acrylonitrile-butadiene-styrene DMT, dimethyl terephthalate EB, ethylbenzene EDC, ethylene dichloride HDA, hydrodealkylation HOPE, high-density polyethylene LDPE, low-density polyethylene PET, polyethylene terephthalate PTA, polyethylene terephthalic acid PVC, polyvinyl chloride SB, styrene butadiene TDI, toluene diisocyanate TDP, thioldiphenol VCM, vinyl chloride monomer. 

Synonyms Diisocyanatoluene 2,4-Diisocyanato-1 -methylbenzene 2,4-Diisocyanatotoluene Isocyanic acid, methylphenylene ester Isocyanic acid, 4-methyl-m-phenylene ester 4-Methylphenylene diisocyanate 4-Methylphenylene isocyanate TDI 2,4-TDI Toluene diisocyanate 2,4-Tol uenediisocyanate Tol uylene-2,4-diisocyanate Tolylene diisocyanate 2,4-Tolylene diisocyanate m-Tolylene diisocyanate... 

Nevertheless all spray foams have the crucial disadvantage that they contain isocyanates, which are critical with respect to toxicological and enviromental impUcations [8]. Monomeric isocyanates like TDI (toluene diisocyanate) or MDI (methylenediphenyl diisocyanate) are even suspected of causing cancer [8, 9]. Although these foams are used even by nonprofessionals, to date there exist no suitable, less endangering substitutes. 

The abbreviations and symbols are as follows MDI methylene diisocyanate, TDI toluene diisocyanate, HuMDI aliphatic MDI, [NCOJo initial isocyanate concentration, PEG poly(ethylene glycol), MW molecular weight, T temperature, k kinetic rate constant, E The Arrhenius activation energy, A pre-exponential factor. It is assumed that the reactions follow an Arrhenius relationship of k = Aexp(—E /PT). 

Mondur XP 7143 Isocyanate-MDI, diphenylmethane diisocyanate Isocyanate-TDI, toluene diisocyanate Bayer... 

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