Synthesis And Modification Of Waterborne Polyurethane Based On Dimer-fatty-acid Polyester Polyol

Dime-fatty-acid polyester polyol (PDFA) could be used as the soft segment to overcome the weaker storage stability and hydrolytic resistance of waterborne polyurethane (WPU). Waterborne ultraviolet (UV) technology is always used to improve the tensile properties with high efficiency. In this thesis, the superiorities of PDFA and waterborne UV technology were simultaneously considered to obtain dime-fatty-acid polyester polyol based WPU with excellent properties.PDFA based waterborne polyurethane dispersions with excellent storage stability and quicker drying rate were synthesized firstly. The study on drying process showed that the PDFA based WPU exhibited the quickest drying rate, which could effectively shorten the drying process and save the energy and time consumption. The sequence of drying rate was as follows: PDFA-PU>PTMG-PU>PCL-PU>PPG-PU. In addition, the hydrolytic stability of PDFA-PU film was also the best and its tensile strength decreased only 14% after 21 days soaking in water.PCL was then used to improve the tensile strength of PDFA based WPU. The results showed that the tensile strength and thermal stability were effectively enhanced due to the incorporation of PCL. When the molar ratio of PDFA/PCL came to 1, the tensile strength increased from 9.97MPa to 15.62MPa. In addition, the glass transition temperature of soft segment also increased from -56°C to -45°C. The degree of phase separation was greatly reduced.Waterborne UV-curable technology was introduced and a series of UV-curable PDFA based WPU with high C=C content were synthesized. The incorporation and reaction of C=C bonds were confirmed by Fourier transform infrared spectroscopy (FTIR). UV curing kinetics was investigated and the results showed relatively higher C=C conversion for PDFA based WPU the maximum could reach to 90.23%. Tensile properties and thermal properties were both successfully improved. After UV curing, it can be seen that the tensile strength was improved from 9.97MPa to 23.3MPa and the maximum could reach to 37MPa due to the increasing crosslink density. The hardness increased from 0.10 to 0.22 and the maximum could reach to 0.78. The glass transition temperature of soft segment increased 8°C and the hard segment glass transition temperature increased 6°C. In addition, thermal stability can be increased for 50°C. Based on the studies above, we successfully obtained dime-fatty-acid polyester polyol based WPU dispersions with excellent storage stability and their tensile strength were effectively enhanced by the incorporation of PCL and the application of waterborne UV technology. In this way, the efficiency of waterborne UV technology could be improved and dime-fatty-acid polyester polyol could be better applied to the industrial manufacturing of waterborne polyurethane materials.