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PubMed2002

[Development of morphology and mechanical properties in polyurethane-urea(PUU) curing process].

The development of morphology and mechanical properties of PUU in bulk prepolymer polymerization process was investigated by TEM and in situ FTIR. The data from the FTIR spectra showed that the absorbance of NH band was becoming sharp and its band sites shifted to lower wavenumbers with the increase of reaction time, the absorbance of free urethance carbonyl kept nearly constant at low conversion, and then became weaker, and finally became little because of strong hydrogen bond affect of more and more new wrealink group at high conversion. With increasing of the reaction time, the band sites of urea carbonyl also shifted to the lower wavenumbers and at the same time, the absorbance of ordered urea carbonyl became sharper and sharper. The carbonyl bands vibration models available during curing process were further assigned. The photos of TEM showed that the domains of hard segments became clearer with buildup of hydrogen bond between urealinks.

Cross-Linking Reagents↗
PubMed2000

[Effect of organic tin on the morphology and mechanical properties during polyurethane-urea curing process].

The mechanical properties and morphology of crosslined PUU in bulk quasi-prepolymer process was studied by in situ FTIR. From the quantitative change of carbonyl FTIR spectra, the development of morphology between noncatalyzed and catalyzed polymerization process was discussed in detail. The effect of organic tin concentration on the mechanical properties was investigated. It showed that urea carbonyl splitted many small weak bands at different sites with increasing of organic tin concentration, and the catalyst played an important role in controlling the morphology and mechanical properties. It also showed that the mechanical properties reached extreme value when the rate constant of -NCO/-OH reaction equate the rate constant of -NCO/-OH reaction.

Catalysis↗
PubMed1976

[Occupational dermatoses due to polyurethane drugs].

Twenty cases of occupational dermatoses caused by isocyanates, especially diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI) and tri-isocyanate-triphenylmethane are reported. The handling of patch test substances is described. Personal in test laboratories have to be considered as persons at risk. Findings give some evidence for cross-sensitization between MDI and the corresponding diamine diaminodiphenylmethane. Moreover, it is supposed that MDI may give rise to cross-sensitization to p-phenylene diamine and chemically related compounds.

Asthma↗