Preparation And Surface Activity Research On Water-borne Polyurethane Emulsions

Compare to traditional polyurethane, polyurethane dispersed in water has advantages ofincombustibility, low-odor and environmental friendliness, but it is restricted in applicationdue to the high polarity of water with surface tension72.8mN/m. The surface tension ofpolyurethane is between40mN/m to55mN/m, which makes the wettability on the surface oflow surface energy materials such as plastic is not good. Moreover, good surface activity isalso required in waterborne ink, waterborne coatings and ceramic squeegee oils. Therefore，itis important to study on waterborne polyurethane of high surface activity.Three sulfonate chain extenders were synthesized with ethanediamine, D230andhexamethylenediamine as materials, the optimum reaction conditions were as follows: solventamount of10of substrate, at(1∶1.1) mole ratio of diamine and1,3-propane sultone, the yieldcan achieve92%. However, stable polyurethane emulsion can’t be prepared with those chainextendersA kind of nonionic water-borne polyurethane emulsions (WPU) were synthesized withthe raw materials of polyether glycol PE6100(with EO and PO), toluene diisocyanate (TDI)and polyetheramine ED-2003as hydrophilic extender. In this structure, the hydrophilic andlipophilic groups were distribution uniform and the PO chain was long, which led to asignificant reducing on surface tension of WPU.Their structures were characterized byFourier transform infrared spectrum analysis. The partical size, viscosity and surface activity,including surface tension, critical micelle concentration (CMC) in the aqueous solution wereinvestigated. Results showed that they can be kept at least6months, with partical sizesbetween100nm and400nm. The partical sizes increased and viscosities decreased when thehydrophilic group content decreased and the nNCO/OH increased. Their viscosities decreasedwhen the shearing rate increased, exhibiting rheology behavior. Moreover, they have lowercritical micelle concentration (CMC) and excellent surface activity with surface tensionincreased when EO content increased.Inorganic pigments like titanium white are often used in ink and coatings, they are badlycompatible with polyurethane so that the system is unstable. γ-amino propyl triethoxy silane(KH-550) contains ethoxy and amino groups, ethoxy group is hrdrolyzed into silanol which conbines with inorganic pigments to form siloxane (Si(OH)3), and amino group reacts with–NCO to reinforce the bond strength. Therefore, the compatibility was improved by addingKH-550into polyurethane to build a bridge between inorganic pigments and polyurethane. Inchapter3, WPU were modified with KH-550, and results showed that their surface activityincreased after modification, the partical sizes and viscosities increased with KH-550contentincreased. In a word, there are good application prospect of the WPU synthesized inwaterborne ink and ceramic squeegee oils because of their high surface activity and stability.