Study On Preparation And Applied Performance Of Polyurethane Adhesive For EMU Carbody

With the rapid development of the railway transportation industry in China,more high-quality related requirements have been proposed to the functional materials applied for the body of the EMU.As an important constitute of the relevant parts during the bonding process of the car body,the properties of adhesive would be affected by the complex environmental conditions,including the temperature,humidity,salt spray and sun light,etc.,which exist during the actual operation of the EMU.Afterwards,the mechanical properties and service life of additive would be deteriorated dramatically.In this study,from the viewpoint of the practical applications,the silane-modified polyurethane adhesives for vehicles were firstly manufactured,and the aging behaviors of the commercial polyurethane adhesives were investigated.The main research contents are as follows:The silane-modified polyurethane adhesives were prepared,and the influence of the silane coupling agent dosage,R-value,and molecular weight of polyether diol(PD)on its properties was explored.The results showed that with the increase of the silane content,the viscosity of the prepolymer and water adsorption value both firstly reduced and then increased,while the surface drying time of the adhesive decreased.Moreover,In addition,the higher siliane dosage would be beneficial to enhance the tensile strength and the Shore A hardness obviously,and the corresponding elongation at break declined.As the R-value increasing,the viscosity of the pre-polymer markedly strengthened,while the surface drying time was shortened.Moreover,the parameter of water absorption for additive decreased first and then increased.Meanwhile,the tensile strength and Shore A hardness improved significantly,and the elongation at break decreases.Further,the increase of the molecular weight of PD additive remarkably improved the viscosity of the prepolymer,while decreased the water absorption of the adhesive.At the same time,the surface drying time decreased first and then increased.Besides,the tensile strength and Shore A hardness both decreased,and the elongation at break increased.Based on the experimental results,the prepared adhesive showed the most excellent overall performance with the tensile strength of 7.66 MPa and an elongation at break of 520%,when the silane content,R-value and molecular weight of PD polyether was 3,1.3 and 1000,respectively.The mechanical properties of the two adhesives after different aging conditions were characterized.The results showed that as the aging time increased,the tensile strength decreased.In detail,under the high temperature(T)conditions,different humidity(RH)has a significant effect on the tensile strength.Meanwhile,under the low humidity(RH)conditions,the influence of different temperatures(T)on the tensile strength could be ignored.Finally,under the high humidity(RH)environment,the different temperatures(T)significantly affected the tensile strength.Two different types of bonding specimens were prepared with the two optimum adhesives,and the shear strength values of aged samples with various aging conditions were measured.The results revealed that the temperature and humidity are the most significant factors affecting the shear strength.To quantitatively evaluate the influence,a generalized The Eyring model was established to simulate the effective service life of the adhesive.The simulation results indicated that regarding the synthetic silane-modified polyurethane adhesive,the simulated service life for bonding of window glass was approximately 16 years,while the service life of simulated bonding for locomotive lights could reach to 42 years.For the commercial polyurethane adhesive obtained from the market,the potential service life of car window glass bonding was only 11 years,and the service life of simulated locomotive lamp bonding was about 39 years.