Study On The Processing Materials Of UV-curing Three-dimensional Printing

UV-curing Three-dimensional Printing (3DP) is similar to UV ink-jet printing, whichis the spray forming of UV resin droplets. In the forming process, two sets of printingheads simultaneously spray UV-curing building material and UV-curing support material,respectively. Then the materials are cured by ultraviolet light. The materials accumulatelayer by layer. Lastly, when the printing is completed, removing the support material bywater gun, the prototyping part is achieved. UV-curing Three-dimensional Printingcombines the advantages of UV-curing and spray forming, to improve the efficiency andaccuracy of rapid prototyping and reduce costs.UV-curing building material and UV-curing support material is crucial for UV-curing3DP. At present, only 3D Systems Corporation and OBJET Corporation can supplyUV-curing Three-dimensional Printing machines and forming materials, and the sprayingtemperature of UV materials is 100-110℃and 70-75℃, respectively. It is the first teamfor us to research on UV-curing three-dimensional printing equipment and formingmaterial at home, and XAAR XJ500 is the printing head, with material sprayingtemperature of 50-55℃. The lower spraying temperature is, the less is suitable rawmaterial, and the more difficultly will we research on the forming materials. Therefore, thepreparation and properties study of UV forming materials is of vital importance.This paper researches on the theory and experimental method of the critical exposure,penetration depth, contractility, curl distortion of UV resins. Droplets formation andspraying process of piezoelectricity printing head are described, and spraying processparameters, spreading and wetting parameters are discussed. It is the theoretical principleof the preparation and properties study of UV forming materials.The polypropylene glycol diglycidylether diacrylate was synthesized bypolypropylene glycol diglycidylether and acrylic acid as two main materials. Thepreferable synthesizing conditions as below: the temperature is 100-110℃, the catalystmass fraction of N,N-dimethyl benzylamine is 0.80% and the inhibitor mass fraction ofp-hydroxyanisole is 0.20-0.40%. The hybrid building material was prepared bypolypropylene glycol diglycidylether diacrylate, cycloaliphatic epoxide, oxetane and vinylether as the main materials. The parameters and experiment results of the hybrid buildingmaterial indicated that, it has good photosensitive, and can be sprayed steadily at 55℃, the cured building material has excellent mechanical and thermal properties.The free radical building material's oligomer of low viscosity urethane acrylate wassynthesized by TDI, HEA and PEG as three main materials. The preferable synthesizingconditions as below: at the first step, n(TDI):n(HEA)=1, the catalyst mass fraction of DBTis 0.2%, the temperature is 40℃, reaction time is 2-3 hours; at the second step,n(TDI):n(PEG)=2, the temperature is 55-60℃, reaction time is 5-6 hours. The free radicalbuilding material was prepared by low viscosity urethane acrylate as the main materials.The parameters and experiment results of the free radical building material demonstratedthat, it can be sprayed steadily at 50℃, but it's photosensitive and contractility is poorerthan other two building materials.This paper investigates the effect of the benzyl alcohol on cationic building material.Benzyl alcohol and its analogues with electron-donating substituents are usefulaccelerators for the cationic polymerization of cycloaliphatic epoxide and oxetane. Theaccelerated nature is activated monomer mechanism and the free-radical chain-induceddecomposition of onium salt cationic photoinitiator.Oxetane is a kind of raw material in cationic building material. Thephotopolymerization kinetics of oxetane is studied by RT-FTIR technique. Throughanalyzing the photopolymerization mechanism of oxetane, it disclosed that the lastelementary reaction's activation energy is maximum, once heat of reaction overcomeactivation energy, the reaction velocity is very fast.The blue cationic building material was prepared by cycloaliphatic epoxide, oxetaneand vinyl ether as three main materials. The parameters and experiment results of thecationic building material indicated that, it has good photosensitive, and can be sprayedsteadily at 55℃, the cured cationic building material has appropriate mechanical andthermal properties.The support material was prepared by water-borne polyurethane acrylate,polyethylene glycol (1000) diacrylate and PEO-PPO-PEO as the main materials. Thepreferable synthesizing conditions of water-borne polyurethane acrylate is as below: at thefirst step, the temperature is 30℃, reaction time is 1.5 hours; at the second step, thetemperature is 45-50℃, reaction time is 3.5 hours; at the last step, the temperature is50-55℃, reaction time is 5 hours. When TDI:DMPA:PEG is 4:2:1, acid value ofwater-borne polyurethane acrylate is 66.5 mgKOH/g, and it gain excellent water solubilitywith 100% triethylamine to neutralize. Polyethylene glycol diacrylate was synthesized by polyethylene glycol sodium with acryloyl chloride. The support material possesses goodspray stability, but the photosensitive of the support material is worse than buildingmaterials. The experiment demonstrated that UV cured support material can easily peeledby water gun.