Research On Viscoelasticity And Tribological Properties Of Ethylene Propylene Diene Monomer Seals

With the development of economy,science and technology,shield machine is being used in an increasingly wide range of applications.With the increase of application fields,the performance and stability of shield machine are required to be higher.The main drive system is the main output part of the shield machine,and the operating condition of main drive system is one of the important factors affecting the performance and stability of shield machine.The main drive sealing system is an important part of main drive system to ensure normal operation.The main drive sealing system not only prevents external sand,mud and groundwater from entering the interior of main drive system,but also prevents the leakage of lubricating oil.The main drive sealing system consists of a variety of sealing forms.The performance of rubber parts in the main drive sealing system is one of the key factors affecting the reliability and sealing performance.Ethylene Propylene Diene Monomer(EPDM)has excellent ageing resistance,water resistance,high temperature resistance,ozone resistance and corrosion resistance.At present,the rubber has become one of commonly used materials for rubber parts in the main drive sealing system.With the application of blending,grafting,copolymerization and compounding,the performance of EPDM is improved to a certain extent,but the research on the effect of reinforcement and accelerator systems on the viscoelastic and tribological properties of EPDM and on the stick-slip phenomenon and wear mechanism of EPDM under different normal load and sliding velocity conditions are still limited.Reinforcement and accelerator systems are important factors to improve the viscoelastic and tribological properties.Normal load and sliding velocity are key factors to test the sealing performance and tribological properties.Therefore,the effect of reinforcement and accelerator systems on the viscoelastic and tribological properties of EPDM in the main drive sealing system of shield machine are studied,and the content of carbon black and accelerator is optimized.The stick-slip phenomenon and wear mechanism of EPDM under different normal load and sliding velocity conditions are systematically analyzed and studied.EPDM with different content of carbon black and accelerator CZ are prepared separately.The storage modulus,loss modulus and loss factor of EPDM with different content of carbon black and accelerator CZ are obtained by dynamic thermomechanical analyzer,and the effects of content of carbon black and accelerator CZ on the dynamic viscoelasticity,glass transition temperature and vibration absorption capacity of EPDM are analyzed.The tribological properties of EPDM with different content of carbon black and accelerator CZ under dry friction conditions are tested by UMT-Tribolab friction and wear tester,and the real-time curves of coefficient of friction,friction force and change of friction force of EPDM with different content of carbon black and accelerator CZ are obtained.The effects of content of carbon black and accelerator CZ on wear resistance of EPDM are analyzed.The stick-slip behavior of EPDM with different content of carbon black and accelerator CZ is investigated,and the composition of groups and compounds in EPDM with different content of carbon black and accelerator CZ is revealed by Fourier transform infrared spectrometer and X-Ray diffractometer.The wear morphology of EPDM with different content of carbon black and accelerator CZ is characterized by scanning electron microscope,and the wear forms and wear mechanisms of EPDM with different content of carbon black and accelerator CZ are systematically analyzed and studied.The results show that the viscoelasticity and tribological properties of EPDM can be improved by increasing the content of carbon black and optimizing the content of accelerator CZ.The Shore hardness,elasticity and tribological properties of EPDM are better,when the mass of carbon black and accelerator CZ are 70 phr and 0.5 phr respectively.Although the content of carbon black and accelerator CZ changes,the hysteresis and stick-slip phenomena occur in the friction and wear process of EPDM,which results in the change of fluctuation degree of real-time curves of friction and coefficient of friction.The tribological properties of EPDM are tested under different normal load and sliding velocity conditions by UMT-Tribolab friction and wear tester under dry friction condition,and the real-time curves of coefficient of friction,friction force and location of EPDM under different normal load and sliding velocity conditions are obtained.The effects of normal load and sliding velocity on the coefficient of friction,noise intensity and stick-slip behavior of EPDM are systematically analyzed and studied,and the composition of groups and compounds in EPDM before and after wear under different normal load and sliding velocity conditions is revealed by Fourier transform infrared spectrometer and X-Ray diffractometer.The wear morphology of EPDM under different normal load and sliding velocity conditions is characterized by scanning electron microscope,and the effects of normal load and sliding velocity on wear form and wear mechanism of EPDM are analyzed.The results show that the increase of normal load and sliding velocity dose not lead to the change of composition of EPDM before and after wear,but leads to the enhancement of intensity of noise generated in friction and wear process.Under various normal load and sliding velocity conditions,the stick-slip phenomenon occurs in the friction and wear process of EPDM,which results in the change of fluctuation degree of real-time friction and coefficient of friction curves.With the increase of normal load,the wear form of EPDM changes,and the hysteresis degree increases first and then remains constant.The increase of sliding speed leads to not only the decrease of friction coefficient but also the weakening of hysteresis degree during friction and wear process of EPDM.