Naphthalene Diisocyanate NDI

Diphenylmethane diisocyanate (MDI) 1,5-Naphthalene diisocyanate (NDI) Hexamethylene diisocyanate (HDI) Polymethylene polyphenyl isocyanate (PMPI) Isophorone diisocyanate (IPDI) Trimethylhexamethylene diisocyanate (TMDI) 

Relatively volatile Low volatility Dust hazard only Relatively volatile Low volatility Low volatility Low volatility 

Although this is a solid (melting point 127°C) and hence has a dust toxicity hazard, as do all solid isocyanates (e.g. pure MDI of melting point 38°C), it should be considered as having a hazard comparable to TDI as manufacturing processes involve melt reactions at about 130°C. At temperatures in this range, volatilization of the isocyanate occurs comparable to TDI vapour volatilization at room temperature sensitizis-ation of people occurs under these conditions. 

It can be seen that isocyanates which are considered harmless at ambient temperatures due to their low pressures become health-hazardous materials when heated to elevated temperatures for processing. 

The relative volatilities of common industrially used diisocyanates are given in Table 14.3. Vapour-pressure characteristics of TDI and MDI are given in Fig. 14.1 these are usually used as reference materials for toxicity purposes with TDI being considered to have a high toxic-vapour hazard and MDI a low toxic-vapour hazard. 

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NaOH-catalyzed resole resin, 409 Naphthalene diisocyanate (NDI), 201 Naphthalene tetracarboxylic dianhydride (NDTA), 282... 

The isocyanates form the major part of the hard or rigid phase of the polyurethane. The three main isocyanates used in industry for castable materials are toluene diisocyanate (TDI), 4,4 diphenylmethane diisocyanate (MDI), and 1,5-naphthalene diisocyanate(NDI). Aliphatic diisocyanates form a small segment of the diisocyanate market. 

The unstable prepolymers are typified by the Bayer Vulkalon polyurethane. Vulkalon is generally made by reacting naphthalene diisocyanate (NDI) and hydroxyl terminated polyesters to form a prepolymer. The reactivity of the... 

MIC is less frequently used than toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), hexamethylene diisocyanate (HDI), and other isocyanates. In order to highhght the distinctiveness of MIC toxicity, the toxicity of diisocyanates is described briefly. 

The results of our studies will be presented in three sections. Tne first deals with the fluorescence properties of model naphthyl carbmates. This first section is particularly important in furnishing the background necessary to interpret the results in the next two sections vrfiich are concerned with the fluorescence of naphthalene diisocyanate (NDI) based polyurethanes in solution and film. 

Other example isocyanates commonly used in PUs applications are shown in Fig. 1.8. A series of model conventional aromatic diisocyanates is depicted 4,4-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI) and 2,4-tolylene diisocyanate (TDI), most common commercially as an 80 20 mixture of the... 

Only the diisocyanates are of interest for urethane polymer manufacture and relatively few of these are employed commercially. The most important ones used in elastomer manufacture are the 2,4- and 2,6-toluene diisocyanates (TDl) 4,4 -diphenylmethane diisocyanates (MDI) and its aliphatic analogue 4,4 -dicyclohexylmethane diisocyanate (Hi2 MDI) 1,5-naphthalene diisocyanate (NDI) 1,6-hexamethylenediisocyanate (HDI) xylyene diisocyanate (XDI), isophorone diisocyanate (IPDI) and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (TMDI). Also manufactured commercially are various monoisocyanates, including methyl, /7-propyl, /7-butyl, cyclohexyl, phenyl, and 4-chloro- and 3,4-dichlorophenyl isocyanates which are used for substituted ureas and carbamates important as herbicides and crop protection agents. 

The most commonly used difunctional isocyanates are TDI, MDI and 1,6-hexamethylene diisocyanate or 1,6-diisocyanatohexane (HDI). TDI often contains mixtures of the isomers 2,4-TDI and 2,6-TDI. MDI is industrially used as a mixture of 4,4 -MDI with 2,4 -MDI and 2,2 -MD which is also called polymethylene polyphenyl isocyanate (PAPI or PMPPI). Phenyl isocyanate is usually a trace constituent in commercial MDI products. Examples of other diisocyanates include isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), naphthalene diisocyanate (NDI), triphenyl-methane triisocyanate (TPMTI), and DMDI (Malten 1977> 1982, i984a,b, i987a,b Bjorkner 1992 Elvers et al. 1991 Estlander et al. 1992 Karol and Kramarik 1996). 

Polyimides are also obtained in one step in the reaction of diisocyanates with tetracarboxylic acid dianhydrides. As an example, BTDA is reacted with a mixture of 2,4-TDI and MDI in DMF (93). This copolyimide, PI 2080, is used as a high temperature fiber and it is also sinter molded into solid shapes with exceptional mechanical properties. From PMDI and benzophenone-tetracarboxylic acid dianhydride polyimide foams with outstanding thermal properties and flame resistance are produced (94). Pol5fimides derived from p-phenylene diisocyanate (PPDI) or naphthalene diisocyanate (NDI) and pyromellitic dianhydride or BTDA are also synthesized using DMAc as solvent (95). 

Several higher-priced aromatic diisocyanates, such as p-phenylene diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI), and bitolylene diisocyanate (TODI), are also available. These symmetrical high melting diisocyanates give high melting hard segments in polyurethane elastomers. 

Commonly used isocyanates include toluene diisocyanate (TDl), methylenediphenyl diisocyanate (MDl), naphthalene diisocyanate (NDI), and hexamethylene diisocyanate (HDI). All isocyanates are toxic (Rye, 1973) to varying degrees TDl seems to be the most toxic. 

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