| Solvent-free two-component polyurethane adhesives have been paid more and more attention and welcomed by the polyurethane industry due to their lack of VOC emission and numerous advantages.In this paper with castor oil,liquefied MDI and epoxy resin E51 as raw materials,a type of solvent-free polyurethane with epoxy sealing ends were prepared.At the same time,the selection of raw materials,preparation methods and properties of the adhesives were studied.The results showed that the prepared adhesives have excellent properties and are convenient for transportation and storage.The hardness of the adhesives reaches 86 Shore D hardness,impact strength reaches 60.5k J /m2,and shear strength reaches 24.27 MPa.The influence of the amount of raw materials,reaction temperature,isocyanate value and reactive diluents on the preparation of PU/EP adhesives was investigated and the process of epoxy-terminated polyurethane grafted epoxy resin polymer was determined.The results showed that the best preparation process is preparing the polyurethane prepolymer at 75°C for 3.5h,then-increasing the temperature to 80°C,adding epoxy resin E51,catalyst dibutyltin dilaurate and active diluen.Finally the component A of castor oilbased polyurethane grafted epoxy resin E51 adhesive were obtained,which were characterized by the infrared spectrum.With three different curing agents(T31,polyetheramine(D-230)and polyamide(650))as the two-component polyurethane B component,we explore the effects of curing process of different curing agents,different curing agents and different reactive diluents on the mechanical properties and thermodynamic properties of PU/EP adhesives.The results show that the curing process of T31 curing system is 26℃/2h+75℃/2h.The curing process of polyamide(650)curing system is 50℃/2h +90℃/2h;The curing process of polyether amine(D-230)curing system was 75℃/2h+125℃/3h.With D-230 is as curing agent,the PU/EP adhesive has the best comprehensive performance when the active diluent is added at 15%.The hardness of Shore D reaches to 75 HD,the tensile strength is 66.72 MPa,the elongation at break is 12.35%,the impact strength is 48.42 MPa,and the tensile shear strength is 15.76 MPa.By DSC,it was found that the compatibility of each component in the PU grafted EP system was good,and the glass transition temperature was obviously lower than that of epoxy resin.TG and DTG analysis showed that the thermal stability of PU/EP adhesive was significantly higher than that of EP adhesive.The modification degree of KH560 on different fillers and the influence of different fillers and content on the mechanical properties,thermodynamic properties and surface morphology of PU / EP adhesive were investigated by filling three kinds of inorganic fillers,namely calcium carbonate,calcium sulfate and barium sulfate.The results showed that the hydrophobicity of inorganic filler can be improved obviously by the contact Angle analysis after the modification of KH560 coupling agent.The modification effect of calcium carbonate is the best,and the contact Angle reaches 95.5°.It was found that calcium carbonate had the best filling effect when the filling content was 30%.Hardness reached to Shore D hardness 86;The impact strength reaches to 60.5k J /m2,which is 24.9%higher than that of PU/EP without filler.The shear strength of PU/EP reached 24.27 MPa,which was 54% higher than that of PU/EP without filler.Through the microstructure analysis,DSC analysis and TG analysis of PU/EP adhesive,calcium carbonate can effectively enhance the performance and heat resistance of PU/EP adhesive. |
