Preparation and characterization of waterborne polyurethanes modified with bis(3-(1-methoxy-2-hydroxypropoxy) propyl) terminated polysiloxanes

Abstract

Polyurethanes (PU) were prepared using toluene diisocyanate, polypropylene glycol, ethylene glycol, dimethylolpropionic acid and triethylamine, and a siloxane modified PU (PSU) was obtained through reaction of the PU prepolymers with bis(3-(1-methoxy-2-hydroxypropoxy)propyl) terminated polysiloxanes (PMTS) of different molecular weight, specifically designed for this purpose. Results showed that, with increases in molecular weight of PMTS and its content, viscosity of the final PSU latexes decreased; phase separation of the incorporated PMTS in PSU films increased; the average particle sizes of the latexes varied between 110 nm and 330 nm, and the surface tension in the final latexes was relatively constant regardless of PMTS amount and its molecular weight. It was likely that copolymerized polysiloxanes had trend to enrich on top of the film when PMTS molecular weight was around 2000 and its content above 5 wt%. In general, PMTS modified polyurethane films showed higher performance than those from unmodified waterborne polyurethane latexes.