SYNTHESIS AND PROPERTIES OF WATERBORNE POLYURETHANES MODIFIED BY EPOXY RESIN
A series of anionic waterborne polyurethane emulsion modified by epoxy resin were successfully prepared by the reaction of polycaprolactone diols (CAPA), isophorone isocyanate (IPDI), hexamethylene-1,6-diisocyanate (HDI) and epoxy resin (E-44) as crosslinker. Solidified films of the waterborne polyurethane were prepared by casting emulsions on Teflon surfaces. Fourier transform infared spectrometer (FTIR) and thermogravimetry analysis (TGA) were used to characterize the structure of the polyurethane. The mechanical properties and water contact angle of the cast films were also measured. The surface roughness and surface morphology of the films of waterborne polyurethanes were observed by atomic force microscopy (AFM). The particle size and distribution of the resultant polymer emulsions was tested by the dynamic laser light scattering (DLLS). FTIR indicates that epoxy group and hydroxyl group of E-44 both reacted with the polyurethane prepolymer. TGA indicates that the crosslink of E-44 with polyurethane increased thermal stability of the modified polyurethanes. It was found that the tensile strength of films of modified polyurethane increased and the elongation at break decreased with increasing E-44 content, the water contact angle increases with increasing w (E-44), the smoothness of solidified films of waterborne polyurethane decrease when modified by E-44, resulting in water repellence functions. DLLS showed that the particle size of emulsion increased with increasing w (E-44). In order to obtain stable polyurethane emulsions and solidified films of waterborne polyurethanes with improved mechanical properties, the proper w (E-44) is 10%.
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