| As a new type of green environmental protection and energy saving coating,UV-curable waterborne coating has many obvious advantages.In recent years,it is replacing the traditional organic solvent coating and has achieved rapid development.At the same time,compared with the shortcomings of organic photoinitiators such as incomplete curing and volatile organic compounds（VOC）generated by the migration of photolytic small molecules to the surface,inorganic photoinitiators have shown many outstanding advantages,meeting the green development requirements of the new development concept.In this paper,the relationship between the ratio of factors affecting the stability of UV curable waterborne polyurethane acrylate（UV-WPUA）emulsion was designed and studied,combined the dual performance advantages of UV curable technology and waterborne coatings.The organosilicon highly active modified waterborne polyurethane acrylate by UV grafting copolymerization to tune the surface properties of the WPUA composite coating.Inorganic Zn O nanoparticles（Zn O NPs）as photoinitiator have been studied to improve the comprehensive properties of the WPUA coating by UV-curing in the WPUA composite coating after surface modification by organic silicon.The specific work of this paper is as follows:（1）First,vinyl terminated waterborne polyurethane（WPU）was prepared by three-step method,and then the WPUA emulsion was prepared by self-emulsification method.The influence factors on the stability of the emulsion which were the isocyanate index（R）of polyurethane,the addition amount(w DMBA)of hydrophilic chain extender dihydroxymethyl butyric acid（DMBA）and the ratio of PU/PA were studied by FTIR,particle size distribution,water contact angle（WCA）and water absorption.The results showed that the WPUA emulsion had excellent stability when the isocyanate index of polyurethane was R=1.4,the addition amount of hydrophilic chain extender DMBA was w DMBA=0.04,and the ratio of PU/PA was PU/PA=0.6.（2）The WPUA emulsion was prepared on the basis of the previous step,and the organosilicon highly active modified waterborne polyurethane acrylate by UV grafting copolymerization.The Zn O NPs was surface modified by silane coupling agentγ-methacryloxypropyltrimethoxysilane（KH570）,and the organosilicon modified Zn O NPs（Si@Zn O NPs）were used as photoinitiators to prepare the organosilicon grafting copolymerization waterborne polyurethane acrylate composite coating（WPUA@KH570）with high ultraviolet absorption,surface properties and water resistance by UV-curing.The effects of the organosilicon grafting copolymerization on the properties of the WPUA@KH570 composite coating were characterized by FTIR,XRD,WCA,UV-vis absorption spectra,water absorption and SEM.The results showed that when the content of Si@Zn O NPs reached 1.5 wt%,the absorbance to ultraviolet was 0.5,the water absorption decreased to 15.41%,and the water contact angle increased to 90.61°,the WPUA@KH570 composite coating changed from hydrophilic to hydrophobic,and the surface properties,water resistance and ultraviolet absorption of the composite coating were improved.（3）Based on the previous two steps,three kinds of Zn O NPs with different morphologies were designed and prepared,and the Zn O NPs with the best effect on UV initiation were selected as photoinitiators.A series of waterborne polyurethane acrylate composite coatings（WPUA@Zn O NPs）with different contents of Zn O NPs were prepared by modified Zn O NPs with silane coupling agent KH570.In addition,three fabric-based materials（cotton,PET and PP）were immersed in the WPUA@Zn O NPs emulsion to prepare three kinds of fabric-based coatings.The effects of different contents of Zn O NPs and different coating layers on the properties of three different fabric-based coatings were investigated by FTIR,XRD,SEM,specific surface area（BET）,thermogravimetry（TG）,pencil hardness,UV-vis absorption spectra,mechanical properties,WCA and water absorption.The results showed that the absorbance of the WPUA@Zn O NPs composite coating was 40.28%higher than that of the WPUA@184composite coating.Compared with the PP-WPUA@184 coatings,the stress and strain of the PP-WPUA@Zn O NPs coatings increased by 41.19%and 34.39%respectively.At the same time,the hydrophilicity and hydrophobicity of the interface of the fabric-based coatings changed.Functional Zn O NPs in the WPUA@Zn O NPs composite coating not only acts as photoinitiator,but also acts as inorganic nano filler,improve the ultraviolet absorption ability of the composite coating,and the mechanical properties,interface properties,wear resistance,water resistance and acid and alkali resistance of the fabric-based coatings.Figure 34 table 15 reference 194... |
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