Study On Photo-Polymerizable ZnO Photo-initiators And Photo-induced Self-curing Polyurethane Acrylate Pre-polymers

Waterborne polyurethane acrylate is the most commonly used UV curing resin.However,due to the incomplete curing and the use of photo-initiators,photolyzed small molecules will migrate to the surface of the film after UV-curing.The self-initiated photo-curing resin doesn't use photo-initiators,which can eliminate the photolysis small molecules'VOC caused by the use of photo-initiators.Then,it is more environmental-friendly.In this thesis,waterborne polyurethane acrylates with high degrees of self-initiated UV-curing and polymerizable Zn O photo-initiators were synthesized.Both of them had good overall performances.The self-initiated photo-curing resins with photo-curing degrees of over 90%were synthesized through the molecular design and raw material optimization,which used toluene diisocyanate?TDI?,polyether 1000?N210?,dimethylolpropionic acid?DMPA?,2-Hydroxyethyl methacrylate?HEMA?,pentaerythritol triacrylate?PETA?and triethylamine?TEA?as main raw materials.Factors,such as the species of neutralizer,the degrees of neutralization,the values of?NCO/OH?_initial and the types and ratios of hydroxyl acrylates that influences the degrees of UV-curing,and the properties of the film,were investigated.The pre-polymers were characterized by Fourier transform infrared spectroscopy?FTIR?,¹H-NMR spectrum?¹H NMR?and gel permeation chromatography?GPC?,the UV-cured films were characterized by thermogravimetry analysis and different scanning calorimetry?DSC?.When triethylamine was used as the neutralizer,the degree of neutralization was100%,the?NCO/OH?_initial was 5,and the HEMA/PETA ratio was 2/3,then,the self-initiated photo-curing degree of the pre-polymer would be optimized to be the highest values.The GPC test showed that the pre-polymer had a concentrated molecular weight distribution.TG analysis and DSC analysis showed that the film had good thermal stability.The surface of ZnO was modified with TDI and hydroxyl acrylates to prepare the polymerizable Zn O photo-initiator.Then the polymerizable ZnO photo-initiator/waterborne polyurethane acrylate pre-polymer was prepared with it.ZnO was characterized by FTIR,UV spectroscopy,particle size analysis,Zeta potential measurement,X-Ray diffraction?XRD?,TG analysis,and energy dispersive spectrum?EDS?before and after the modification.The results showed that TDI was used as coupling agent to graft-C=C-groups onto the surface of ZnO,and the agglomeration of ZnO decreased after the modification.The dispersion stability of Zn O in organic solvent was increased.XRD results indicated that the crystal form of ZnO was slightly changed after the modification.TG test showed that the grafting amount of organic on the surface of ZnO was about 4.2%.For the UV-cured film,the addition of polymerizable ZnO photo-initiator could improve the hardness of the film and enhance the water resistance and the adhesion of the film.With the increase of the content of polymerizable ZnO photo-initiator,the gel rate increased gradually.When adding polymerizable ZnO photo-initiator prepared with different hydroxyl acrylate,the gel rate of the pre-polymers didn't change much.The photo-curing kinetics of the composite pre-polymers were studied by real-time UV spectra.The results showed that the UV-curing reaction was a zero-order reaction,the UV-curing reaction rate constant increased with the increase of the content of polymerizable ZnO photo-initiators.