| As a kind of green environmental-friendly materials,the waterborne UV curable materials not only inherit the advantages of high efficiency,environmental protection,economy,energy saving and wide adaptability of the UV-curable materials,but also avoid the use of a large number of organic solvents and active diluent monomers.However,there are still some problems in the application of waterborne UV curable materials such as poor water resistance,heat resistance and mechanical properties.Therefore,the development of waterborne UV curable materials with excellent water resistance,heat resistance and mechanical properties has importantly theoretical and practical significance.The polyurethane acrylates combine characteristics of both polyurethane and acrylates,while the organosilicon has high heat resistance,good weatherability and low surface energy,moreover,there are many factors that greatly influence the properties of oligomers such as the functionality of polymerizable double bonds,the position of double bonds and organosilicon segments in oligomer molecules,and the types and contents of hydrophilic groups.Based on this,a series of novel waterborne UV-curable organosilicon-containing polyurethane acrylate oligomers with high water resistance,excellent heat resistance and good mechanical performance was designed and synthesized by introducing several double bonds in the molecular side chains,linking organosilicon segments at the end of the molecular main chain and combining non-ionic hydrophilic ether chains with hydrophilic ionic groups.The study of this subject will provide a theoretical basis for the design of waterborne UV-curable materials with high performance,and broaden their application areas.The main conclusions are as follows:(1)Firstly,2,2-bis(hydroxymethyl)butyl acrylate monomer(HBA)was synthesized from trimethylolpropane,2,2-dimethoxypropane and acryloyl chloride in three steps,and then single-ended hydroxyl polydimethylsiloxanes with different chain lengths were synthesized from hexamethylcyclotrisiloxane,n-butyllithium,dimethylchlorosilane and allylhydroxyethyl ether in two steps.Finally,twelve waterborne oligomers with different organosilicon chain length,organosilicon content or carbon-carbon double bond content were prepared from aliphatic glycol(PCDL-2000),polyethylene glycol(PEG-400),2,2-bis(hydroxymethyl)butyl acrylate(HBA),isophorone diisocyanate(IPDI),hydroxy-terminated polydimethylsiloxane with different chain length and dihydroxy polydimethylsiloxane(X-22-160AS).And their structures were characterized.(2)Twelve waterborne oligomer emulsions have good storage stability,the particle sizes of emulsions are between 131.7-243.3 nm and the viscosity are lower than 10 cP.The oligomers have high double bond conversion and polymerization rate.(3)The increase of the length of the organosilicon chain which is located in the end of the oligomer chain is benefit for the enrichment of organosilicon on the material surface and the enhancement of the hydrophobicity and heat resistance of the UV-cured films.(4)With the increase of organosilicon content in oligomers,the surface hydrophobicity,and the tensile strength and elongation at break of U-V-cured films gradually increase.When the content of organosilicon is 14%,the water contact angle of the UV-cured film reaches 96°,the tensile strength is 12.3 MPa and the elongation at break is 50.4%.(5)With the increase of the content of carbon-carbon double bond in oligomers,the water absorption rate of the cured films decreases gradually and reaches 2.5%,the gel yield gradually increases to 97.4%,and the hardness gradually increases to 6H.With the increase of the content of carbon-carbon double bond in oligomers,the heat resistance,glass transition temperature and tensile strength of the films also increase.The initial decomposition temperature,Tg and tensile strength are enhanced to 286℃,80℃ and 15.2 MPa,respectively.However,the surface hydrophobicity and elongation at break of the films are reduced. |
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