Structure and Physical Properties in Crosslinked Polyurethanes

Crosslinked polyurethanes based on a mixture of toluene diisocyanate, polypropylene glycol, trimethylol propane (TMP), glycerol (GLY), and desmophen (DES) were synthesized with various ratios of DES and GLY. Chemical crosslinks were introduced through the hard segment (TMP, GLY) and through the soft segment (DES). The effects of the degree of crosslinking on the properties were examined. The crystallinity of the obtained polymers were studied by using modulated differential scanning calorimetry, differential scanning calorimetry, dynamic mechanical analysis and their morphology was studied by atomic force microscopy. It appeared that the degree of crosslinking increased according to the increase of GLY content. Moreover, it was found that chemical crosslinks in the hard segment destroyed the crystallinity of the hard phase and reduced the mobility of the soft phase, improving the heat stability of the hard domains, and modifying the mechanical properties of polyurethane films. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1742-1751, 2011