Segmented polyurethanes 680 INDEX

John et al. (70) studied and compared the properties of polyurethane foam obtained from soybean oil-based polyols and synthetic polyols and found that the soybean-based polyols showed enhanced reactivity and that the foaming reactions proceeded in a very similar way to synthetic polyols. It was also found that their properties were sensitive to several variables such as water content, isocyanate index, and catalysts. The reaction rate was mainly controlled by the water and isocyanate content. As the water content increased, the reaction was faster and the amount of the hard segment increased. In addition, MDl yielded more rigid foams than TDL... 

Molecular models (2) of the hard-segment phase of segmented polyether polyurethanes tested in the in vitro bead column (4) show a high platelet retention index (p = 0.8) regardless of molecular composition. The variable p is defined as the fraction of platelets in whole citrated human blood entering a test column that are retained on the bead surfaces, averaged for... 

Parallel tests show that thrombin adsorption is minimal on well-prepared polyurethanes containing amorphous PEO, greater on PTMO, and very high on analogues of the hard segment (diisocyanate-diamine copolymers), thus paralleling the trends in platelet retention index p. This result is consistent with the postulate that protein adsorption must precede platelet adsorption. 

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