A series of water dispersible polyurethanes containing quaternary ammonium group as the hydrophilic group with different content of trimethylolpropane (TMP) as inner crosslinker were prepared. IR spectroscopy was adopted to demonstrate the polymerization reaction and structure of polymer. The effects of TMP content on PU properties were investigated. Particle size distribution (PSD) analysis and morphology of PU observed by TEM showed that particle size of PU dispersions initially decreased and then increased with increasing TMP content. The viscosity of the PU dispersions with TMP addition was bigger than the PU dispersions without TMP. TG analysis indicated thermal stability and microphase separation degree of PU was enhanced with increasing TMP content. Contact angle and gel content of PU also increased as increasing TMP content. Meanwhile, tensile strength increased and then decreased with the increment of TMP content.

Keywords: cationic polyurethane; crosslinker; particle size distribution; thermal stability; microphase separation