Research On UV-heat Curing Adhesives For Voice Coil Motors

Adhesives for voice coil motors(VCM)are required to have low shrinkage,low coefficient of thermal expansion(CTE),low temperature curing and UV curing,excellent bonding properties and good stability.The traditional heat curing process not only causes component loss,but also has problems such as overflowing,slipping and dislocation,which leads to low production efficiency and poor operability.In this paper,the two-component adhesive was prepared,which could meet the requirements of large-scale industrial continuous production of VCM motors,by means of rapid surface dry by UV pre-curing and then further improving the curing strength by heat curing.The bisphenol A epoxy resin has high molecular rigidity,high crosslinking density and shrinkage,poor toughness and difficulty to release stress.Therefore,the toughening modification of epoxy resin is of great significance to its curing effect.In this study,the polyurethane prepolymer terminated with isocyanate group(-NCO)was synthesized by the reaction of polyether diol with isocyanate,and then reacted with secondary hydroxyl(-OH)in epoxy resin to synthesize polyurethane modified epoxy resin with good toughness.The satisfied UV-heat curing adhesive was prepared by blending polyurethane modified epoxy resin with alicyclic epoxy resin UVR-6110 as prepolymer.The conclusions from the experiments were as followed:(1)When the ratio of raw materials is n(HMDI):n(PTMG):n(E-44)=2.3:1:2,the dosage of diluent IBOA is 20%and the synthetic process is at 65? for 2 h and following at 75? for 50 min,the synthesized polyurethane modified epoxy resin has the best comprehensive properties,whose viscosity is 3.06×105 mPa s(25?),Mn is 1397.53 g/mol,Mw is 2757.51 g/mol,molecular weight distribution index is 1.97,tensile strength is 54.09 MPa,impact strength is 17.80 kJ/m2,bending strength is 97.61 MPa,storage modulus(E')is 2140.69 MPa(30?),loss modulus(E")is 84.52 MPa,and glass transition temperature(Tg)is 104.01?,(2)When the formulation is m(UVR-6110):m(polyurethane modified epoxy resin):m(DEGVE):(Irgacure 261/Irgacure 819):m(BF3-MEA):m(activated silicon micro-powder)=100:20:25:4/0.03:3:30,and the curing process is UV curing for 5 s and following at 90? for 30 min,the two-component adhesive was prepared,which meets the requirements of VCM bonding process and properties,whose shear strength is 21.48 MPa,E' is 2352.84 MPa(30?),E" is 310.49 MPa,Tg is 66.88?,CTE is 83.08 ppm/? at low temperature and 132.03 ppm/?at high temperature.