Self-assembled Two-component Waterborne Polyurethane Coating Structure And Performance

Polyurethane coating (PU) are widely used due to their high performance. However, with the realization of the environmental protection and the statement to reduce the emission of volatile organic compounds, the PU coatings dissolved in organic solvents were not fit of the market. Under this condition, aqueous PU coatings fast developed in recent years, and many new patents and products were reported whose properties were as good as the two-component organic solvent system. But people paid more attention on the synthetic method than on the factors affecting the properties of PU films. This paper studies the effect of Polyol structure, crosslinking agent, percent NCO in prepolymer on the properties of films.In this paper, DSC , TEM, Stress-Strain, rotational viscometer and particle size distribution-meter were used to characterize the phase separation, morphology, mechanical property, viscosity and average particle size, and drew the conclusion as follow:At the fixed hard segment content, when the molecular weigh of soft segment is higher than 1500, the micro-phase separation appeared and the three phase IPN structure were found, the tensile strength and the elongation at break (Eb) increased and the average particle size decreased; the chemical crosslinkage made the micro-phase separation difficult, and as the functionality increased, the micro-phase separation , tensile strength and Eb decreased; at the fixed solid content, with the Wt% of DMPA increasing, the micro phase separation , average particle size and tensile strength were up,and Eb down.Using poly( tetramethylene oxide-caprolactone ) as soft segmentssynthesized MDI-PU aqueous polyurethane coatings, this paper firstly studied the effect of micro-phase separation on the properties of coatings, and found the co-reinforcing effect on the tensile properties of PU films. Through TEM observed nuclear-shell structure in micro-phase. It was not reported in documents.