ADHERENCE OF LIQUID-CRYSTALLINE POLYURETHANES TO STEEL

Linear liquid crystalline (LC) polyurethanes are formed by the reaction of 2,4-toluene diisocyaniate, poly(butylene adipate)s as soft segments and 4,4'-bis-(6-hydroxyhexoxy) biphenyl (BHHBP) as mesogenic unit and chain extender. The mesomorphic behaviour depends on the sop segment length and the hard segment concentration. The adhesion of those polyurethanes used as a primer in the composite basing on steel as substrate and alkyd melamine resin as coating is dependent on the polyurethane structure, the thickness of the polyurethane layer and their drying conditions. The highest wet adhesion strength has been realized by the hard-segment-typ polyurethane composed of TDI and the mesogenic unit BHHBP.