Preparation And Dynamic Mechanical Properties Of Polyborosiloxane Modified Ethylene-Propylene-Diene Rubber

With the development of the railway,the running speed of the train is constantly improving,which requires that the railway pad can realize the adaptive change of stiffness to protect the structure.The aging resistance of traditional railway pad is poor.The variation range of dynamic stiffness under dynamic compression conditions is small,which is difficult to meet existing requirements.Ethylene-Propylene-Diene rubber（EPDM）is widely used in railroad track products.It is characterized by very good resistance to weather and aging.There is a dynamic cross-linked network structure in Polyborosiloxane（PBDMS）,showing a rapid transition in stiffness for high strain rates and maintaining high strength and stiffness under high-speed impact.In this research,PBDMS was used to modify EPDM by blending,aiming to improve the dynamic stiffness of the blended rubber under a high strain rate and maintain the mechanical properties at the same time.Firstly,aiming at the problem of curing system of the blended rubber,this research studied the influence of two common curing systems on the properties of the blended rubber.Secondly,the effect of the blending ratio of PBDMS and PBDMS-SiO₂ on the properties of blended rubber was investigated.Finally,the effect of coupling agents on the dynamic stiffness of the blended rubber was studied.The results are as follows:In the EPDM/PBDMS blended rubber,the vulcanization performance test results showed that the sulfur curing system resulted in a higher degree of crosslinking,shorter vulcanization time,and better elastic recovery of the blended rubber.It was determined that the sulfur curing system was used in this research.With the increase of the PBDMS addition ratio,the vulcanization time（Tc90）of EPDM/PBDMS blends was reduced from 11.42 min to 7.22 min,thus effectively improving the vulcanization efficiency.The processability was improved by decreasing the Menny viscosity.At the compression rate of 120 mm/min,the rate of change of dynamic stiffness increased from 30.04%to 59.72%.The vertical force increased from 840 N to 1030 N.PBDMS made the blends have good processability and dynamic stiffness adjustment ability.In EPDM/PBDMS-SiO₂ blended rubber,the mechanical properties test results showed that with the increase of PBDMS-SiO₂.The tear strength increased from 41.57 kN·m^-1 to 45.30 kN·m^-1.The elongation at break increased from 603%to 707%.The compressive property decreased from 13.19%to 11.60%,maintaining the mechanical properties of EPDM.The aging performance test results showed that the tensile strength retention rate increased from 91.9%to 99.6%,which enhanced the aging resistance of the blended rubber.The temperature of loss peak increased from^-19.95℃ to-5.15℃.The temperature region expanded from 14.2℃ to 20.25℃,expanding the damping performance.The results of the velocity compression experiments showed that the vertical force value increased from 840 N to 1100 N at the compression speed of 120 mm/min.The stiffness change rate increased from 30.04%to 79.14%.PBDMS-SiO₂ significantly improved the dynamic stiffness adjustment ability of the blend while maintaining its mechanical properties.Among the four different types of coupling agents,KH-550 and KH-570 increased the tensile strength of the blended rubber from 18.25 MPa to 19.12 MPa and 19.63 MPa compared to EPS-10.The results of the velocity compression experiments showed that Si-69 increased the vertical force of the blended rubber from 1050 N to 1330 N at a compression speed of 120 mm/min.The rate of stiffness changed from 54.08%to 75.30%.Si-75 increased the vertical force of blended rubber to 1270 N,which increased by 21%.The rate of stiffness change increased to 79.35%,which significantly improved the dynamic stiffness adjustment ability.