Diisocyanate cross-linking agent

An example of the importance of free-volume availabiUty on cross-linking has been reported in the evaluation of a trifunctional derivative of an ahphatic isocyanate which contains an aromatic ring, y -tetramethylxyUdene diisocyanate (TMXDI) [2778-42-9] C 4H N202, as a cross-linking agent for hydroxy-functional resins (15). 

NR can be cross-linked by a blocked diphenyl methanes diisocyanate to produce urethane crosslinks. The cross-linking agent dissociates into two quinonedioxime molecules and one diphenyl methane diisocyanate. The quinone reacts with the rubber via a nitroso group and forms cross-links via diisocyanato group. The performance of this system in NR is characterized by excellent age resistance and outstanding reversion resistance. 

The two polymers that are to be combined do not essentially have different endgroups. It is also possible to combine polymers having the same endgroups by addition of functional cross-linking agents. For example polyesters with OH endgroups and polyethers with OH endgroups can be combined by a reaction with a diisocyanate. 

Toluene diisocyanate is commonly produced as a mixture of the 2,4- and 2,6-iso-niers, that is used as a monomer in the preparation of polyurethane foams, elastomers and coatings, as a cross-linking agent for nylon-6, and as a hardener in polyurethane adhesives and finishes. Polyurethane elastomers made from toluene diisocyanates are used in coated fabrics and clay-pipe seals. Polyurethane coatings made from toluene diisocyanates are used in floor finishes, wood finishes and sealers, and in coatings for aircraft, tank trucks, truck trailers and truck fleets (United States National Library of Medicine, 1997). 

TDI has a flash pt of 132° (open cup) and flammable vapor level limits of 05 to 9.5% 2,4-Tolylene diisocyanate is used as a constituent (cross-linking agent) of polyurethane expls, proplnt binders, and as a component of a ballistic modifier (Refs 2a, 8 9). Se in Vol 8, P6 8-Table 3 under PBX Type Explosives-Composition (listed as Polyurethane in the Binder, % column), and P409-R to P415-Table 17 under B. Composite Propellants ... 

Recently, Komiyama and co-workers have reported the preparation of novel cyclodextrin derived imprinted carbohydrates for the efficient recognition of cholesterol [34]. jS-Cyclodextrin was cross-linked in the presence of cholesterol using different diisocyanates as the cross-linking agents. These cyclodextrin matrices, after removal of the template, exhibited selective preference towards cholesterol compared to the non-templated cross-linked cyclodextrin. 

Toluene diisocyanate is used in the production of polyurethane foams, elastomers, and dyes. It is a cross-linking agent for nylon-6. 

Toluene diisocyanate is a cross-linking agent and both a pulmonary and dermal sensitizer. Most toxicity occurs with repeated exposure. 

These resins are used in counter tops and plastic dinner-ware. It should be possible to replace the carcinogenic formaldehyde with various cross-linking agents, such as glyoxal, bisanhydrides, bisepoxides, bisoxazolines, diisocyanates, and the like. 

The most important use of phosgene is in the preparation of diisocyanates from the corresponding amines. These compounds have reached major importance as blowing agents for elastic and rigid polymeric foams and as cross-linking agents in improved elastomers and polymers. 

ABSTRACT. Smooth and stable cyclodextrin membranes are successfully prepared from the oriented-cyclodextrin-polymers, by drying layers of the polymers. The polymers are obtained by the reaction of the crystal of 3-cyclodextrin-water inclusion complex with hexamethylene diisocyanate as cross-linking agent in anisole. The cyclodextrin membranes exhibit selective permeation of various materials in water. 

Crystals of inclusion complexes of a- and g-CyDs with methyl orange, 4-nitroacetanilide, 2-propanol, and water were successfully fixed with the use of hexamethylene diisocyanate (HMDI) as cross-linking agent. 

It is possible to utilize MDI or another diisocyanate as a suitable supplementary cross-linking agent. 

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