Synthesis and mechanical properties of two-component waterborne polyurethane

The waterborne polyurethane dispersion is synthesized by using polycarbonate diols,hexamethene diisocyanate(HDI)and dimethylol propionic acid(DMPA),and the film is obtained through curing the dispersion.The effects of DMPA content,molar ratio of OH/NCO,and the degree of neutralization on the mechanical performance of the film are analyzed.The results show that the tensile strength and the initial modulus of the film increase first and then decrease with increasing of the molar ratio of OH/NCO.The maximum values of the tensile strength and the initial modulus,and the minimum values of elongation are located at 4∶1 of the molar ratio of OH/NCO;the tensile strength and the initial modulus increase with increasing the content of DMPA,but the elongation decreases;and the minimum values of the tensile strength and the initial modulus,and the maximum values of elongation are located at 100% of the degree of neutralization.