Study Of UV-curable Polyurethane/Epoxy Acrylate Adhesive

ICF （Inertial Confinement Fusion, ICF） is one of the ways to achieve controlledthermonuclear fusion. ICF target is one of the key components of the ICF study, whilethe micro-target ball as deuterium-tritium fuel airlock is a core part of the ICF target.Needs in the the ICF target ball sealing room temperature fast curing, high transparency,good room temperature and low temperature performance adhesives. As commercialavailable low temperature adhesives is difficult to meet the requirements of fast curingat room temperature, while the porperties of the existing UV-curable adhesives at lowtemperature is poor. Polyurethane has excellent low temperature performance, epoxyresin has good bonding properties at room temperature, and polyacrylate has excellentoptical performance, so we select polyurethane acrylate and epoxy acrylate resin asadhesive system’s basic resin. The main contents and conclusions were listed below:（1） A novel UV-curing polyurethane acrylates （PUA） prepolymer contain hydroxy wassuccessfully synthesized and the influential factors were studied. The chemicalconstructions of PUA were characterized by FT-IR. The best formula of PUAadhesive was obtained through single factor analysis. The results showed that whenthe contents of PUA prepolymer and reactive diluent TPGDA was80%and20%respectively, and the contents of photoinitiator1173were3%. The tensile shearstrength of PUA adhesive at room temperature（25℃） and-196℃were5.6MPa and6.8MPa respectively after UV-cured30s.（2） Two kinds of low viscosity epoxy acrylate （EA1, EA2） were synthetized with bis-（2,3-epoxypropyl）cyclohex-4-ene-1;2-dicarboxylate;4,5-epoxytetrahydrophthali-cacid diglycidylester and acrylic acid as main raw materials. The compatibility ofPUA and EA1, EA2were studied. The best proportions were got with tensile shearstrength as index for investigation by compositing the two kinds of resins. Theresults showed that the tensile shear strength of the adhesive system at roomtemperature was improved by adding of EA1, EA2compared with pure PUAadhesive, while the tensile shear strength at-196℃decreased slightly. When theratio of the two resins were1:1, the comprehensive performances of compositeadhesive systems were best. For PUA/EA1system, the tensile shear strength atroom temperature （25℃） and-196℃were6.4MPa,6.2MPa respectively; For thePUA/EA2system, the tensile shear strength at room temperature （25℃） and -196℃were6.6MPa,6MPa respectively.（3） The grafted reaction was studied with EA1, EA2and3-isocyanatopropyltriethoxysilane as main raw materials and the influential factorswere investigated. The surface structures were characterized by FT-IR. Therelationship between the mechanical properties of EA3, EA4and content of IPTSwere studied. The results showed that when the content of IPTS was20%, thetensile shear strength of PUA/EA3adhesive systems at room temperature （25℃）and-196℃were7.2MPa and6.9MPa respectively, which were improved by12.5%and11.3%compared with PUA/EA1composite adhesive systems; ForPUA/EA4system, the tensile shear strength at room temperature （25℃） and-196℃were7.7MPa,7.1MPa respectively, which were improved by16.7%and18.3%compared with PUA/EA2composite adhesive systems.（4） Nano-Si02was modified use2-isocyanatoethyl methacrylate （IEM） as modifier andthe influential factors were investigated. The surface structures and thermalproperty of Si02before and after modified were characterized by FT-IR and Tg.The dispersity of Si02modified in the solvent was studied by SEM. Therelationship between the mechanical properties of PUA/EA3, PUA/EA4compositesystems and Si02modified. The results show that nano-SiO₂dispersed uniformly inthe solvent and the mechanical property of PUA/EA/Si02nanocomposite wasimproved a lot by adding Si02compared with the pure PUA/EA composite systems.Nano-Si02with little contents can enhance EA material’s toughness and strengthsimultaneous. When the contents of SiO₂was6%, the tensile shear strength ofPUA/EA3/Si02nanocomposite adhesives at room temperature （25℃） and-196℃reached the maximum, that is8.5MPa and8.4MPa respectively, wich wereimproved10.4%and18.3%compared with PUA/EA1composite adhesivesystems.（5） Finally，we made the adhesive with PUA/EA composite resin as matrix resin, andsurface modificatied SiO₂as nanofiller. Its curing time at room temperature is short（30s） and the tensile shear strength at room temperature （25℃） and-196℃were8.5MPa and8.5MPa respectively,which can basically meet the requirement ofadhesive in the ICF target ball sealing.