Structure Design And Propertystudy Of Waterborne Polyurethane Ink Binder

A series of waterborne polyurethane(WPU)dispersions wereprepared through two-step polymerization with the poly(propylene glycol)(PPG),isophorone diisocyanate(IPDI),and dimethylolpropionic acid(DMPA)as the raw materials.Measurements including Fourier transform infrared spectroscopy(FTIR),transmission electron microscope(TEM),differential scanning calorimetry(DSC),thermogravimetry analysis(TGA),X-ray diffractometer(XRD),polarizing optical microscopy(POM),contact angle testswere employed to characterize theviscosity,particle size and solid content of prepared WPU dispersions,and the bulk structures,phase separation degree,thermal stability,crystallinity,wettability of WPU films.This paper firstly focused on the study of the effect of themolar ratio of hard/soft segment(rm)on the property of WPU.Secondly,it studied the effect of DMPA,degree of neutralization and chain extending temperatureon the property of WPU.When studying the effect of rm on WPU,it showed that when the rm was 3,4and 5,the gained WPU dispersions have high solid content,up to 40%,low viscosity ranging from 20 mp.s to 50 mp.s,smaller particle sizeranging from 54.7nm to 87.9 nm.All of the dispersions have better electrolytic stability.The filmsof the WPU have lower crystallinity and higher heat resistance.Thethermal stability of the three samples is extended up to about 400oC.The decomposition temperature of hard segment is at around 220-330oCwhile the soft segment is 330-400oC.WPU films have high transmittance ranging from 87% to 99%.Due to these properties above,the WPU can be used directly as waterborne polyurethane ink binder without removing organic solvent.When studying the effect of DMPA,degree of neutralization and chain extending temperature on the property of WPU,it showed that different DMPA content and different degree of neutralization have effects on the storage stability,particle size and viscosity.When DMPA content is larger than 2%,stable WPU dispersions can be gained and its particle size is between 21.5nm and 51 nm.When the neutralization degree is equal to or less than 70%,WPU dispersions are not stable.When chain extending temperature got to 40 ?? 50 ?? 60 ? and 70 ?,the stability of WPU dispersions didn't change obviously,the water absorption of WPU films decreased and the adhesive strength increased.