A theoretical method to calculate the mode of polyurethane（PU） prepolymers grafted to polyacrylic（PAC） was presented. Using hydroxyethyl acrylate（HEA） as coupling agent, polyurethane-acrylics（PU-AC） hybrid latexes were prepared with varying HEA level and the reaction of HEA with PU prepolymers at different temperatures, and PU grafted to PAC was experimentally determined. The results show that PU grafted to PAC regularly increased, and the non-grafted and linear free PU regularly decreased with increase in HEA/NCO（isocyanate group）. The grafted PU on PAC was not proportional to HEA. More than half of linear PU prepolymers were grafted to PAC when HEA was at a low level with HEA/NCO at 0.33. While grafted PU increased to 84.80%（mass fraction）, when HEA/NCO increased to 1.0. The results were interpreted based on the theoretical calculation of PU grafted to PAC by the present method.
Cationic latexes were prepared through emulsion copolymerization of styrene （St） and butyl acrylate （BA） with a cationic surfactant, cetyl trimethyl ammonium bromide （CTAB）. Latex properties, including particle size, size distribution, （ potential, surface tension and monomer conversion, were determined for latexes prepared with different CTAB amounts. Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation. Results showed that both particle size and 6＂ potential were function of polymerization time and latex solids. Parallel emulsion polymerizations with cationic, anionic charged initiator and charge-free initiators were also carried out, the latex properties were determined at different polymerization time. All these results were attentively interpreted based on the mechanisms of emulsion polymerization, surfactant adsorption and latex particle stabilization.
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.
