Preparation And Properties Of Urushiol,Graphene Modified Cathode Polyurethane Electrophoretic Resins

Waterborne polyurethane resins are widely applied for no pollution and environmental friendly feature.In order to improve the performance of water-based polyurethane resin,the modification of urushiol biomass to water-based polyurethane resin was carried out by chemicaly grafting instead of physical blending.The isocyanate modified graphene oxide with larger layer space was also carried out by organo modification of graphene oxide.By the chemical reaction of organo graphene with OH groups,the two dimentional graphene particle chemical-graft hybrid polyurethane resins were prepared instead of traditional physical entrainment composite method.After high speed shear in water,the graphene hybrid polyurethane dispersions were prepared.The wet PU film was coated by electrophoretic process first,and then the polyurethane film with excellent performance was prepared after high temperature baking process.The properties of the water-based polyurethane resin were improved much by the presence of two dimentional graphene particle.The thesis consists of the following three partsIn the first part,hydroxyl-terminated cationic waterborne polyurethane resin modified by urushiol was prepared by stepwise polymerization method.After mixed with organo additives,the cathodic electrophoretic paint was obtained.The effects of urushiol contents on the structure and properties of the polyurethane resins were investigated by Fourier transform infrared spectroscopy(FT-IR),X-Ray Diffraction(XRD)and thermogravimetric analysis(TGA).The results showed that the modification of urushiol on the PU resin improved micro-phase separation of PU,and the order degree of hard segment.With an increase of urushiol in content,the performance of the film showed the rule of first increasing,and then decreasing.Whenthe molar ratio of urushiol to BDO reached a proper value of 1:14,the glossiness,hardness,acid resistance and solvent resistance for the film were desired.The glossiness reached the value of 130,the hardness was about 5H,the acid resistance was around 43 h,and acetone wiping times were about 748 times.The modification of urushiol on the PU resin improved the thermal stability of the polyurethane film.In the second part,the graphene oxide(GO)was dissolved first in N,N-Dimethylformamide(DMF)solvent,then the ultrasonic wave assisted technology was applied to improve the intercalation of isophorone diisocyanate(IPDI)into the graphene oxide layers,and the isocyanate terminated graphene slurry was prepared by chemical reaction of NCO with the OH group of graphene.Then the graphene slurry was centrifuged,washed and dried three times to get the IPDI modified graphene oxide(IPDI-GO).The graphene oxide was characterized by infrared spectroscopy(FT-IR),X-ray diffraction(XRD),thermogravimetric analysis(TG)and transmission electron microscopy(TEM).The results showed that when the ultrasonic time was 6 hours,the modification effect was desired.XRD results showed that the the layer spacing of the modified graphene oxide enlarged from 1.8 ? to 12.1 ?.FT-IR and TG and TEM results implied that isophorone diisocyanate successfully intercalated into graphene layers.In the third part,the preparation and properties of graphene nano-hybrid polyurethane electrophoretic paint were innovatively studied.Nano-hybrid modification of water-based polyurethane resin had been achieved based on in-situ polymerization method using isocyanate-modified graphene oxide as raw material.Polyurethane resin hybridized with graphene two-dimensional particles was mixed with cross-linking agent,organic additives,etc.After shearing and emulsification,polyurethane electrophoretic paint with two-dimensional nano-sheet hybrid was prepared.The electrophoresis process was used to complete the coating of the electrophoretic paint on the surface of the metal device.The polyurethane film was obtained with excellent performance after the wet film being baked.The structure and properties of graphene two-dimensional particle composite polyurethane resin were characterized and analyzed by thermal gravimetric analysis(TG)and X-ray diffraction(XRD).The morphology distribution of graphene in electrophoretic paint was characterized by transmission electron microscope(TEM).The effect of graphene addition on the performance of polyurethane electrophoretic paint film was studied.The results showed that the structural modification of graphene to polyurethanebackbone could promote the microphase separation of polyurethane resin and increase the degree of hard segment.With the increasing in the amount of graphene,the gloss,acid resistance,and acetone-resistant wiping times of the polyurethane film were first increaseing and then decreaseing,and the conductivity gradually increased.When the mass of graphene was 0.3 wt% of the polyurethane resin,the gloss,hardness,and acid resistance of the paint film were optimized,where the gloss was 128,the pencil hardness was 5H,the acid resistance was 41 h,and numbers of wipes for the acetone resistance were about 786.The presence of graphene two-dimensional particles also improved the thermal stability of the polyurethane film.