| Sound absorption and damping materials play a key role in the acoustic stealth of ships and underwater vehicles.With the increasing demand for deep-sea exploration and operations,maintaining good sound absorption performance under high hydrostatic pressure has become the focus of research on underwater sound-absorbing materials.Styrene-butadiene rubber(SBR)is a general-synthetic rubber,its molecular chain contains benzene ring side groups,steric hindrance will affect the intramolecular rotation and frictional movement when the molecular chain segment moves,and it exhibits good damping absorption under normal pressure.It is often used as underwater sound-absorbing material.Under high hydrostatic pressure,due to the problem of modulus mismatch,the damping and sound absorption capacity of SBR is greatly reduced.Eucommia ulmoides gum(EUG),as a natural polymer material,has a high Young’s modulus and can be used in combination with SBR to obtain composite materials with different modulus.In this paper,the co-vulcanization of EUG and SBR was studied,and EUG and SBR rubber composites with different ratios were prepared by blending.The microstructure,dynamic and static mechanical properties of the composites and their relationship were studied.The EUG/SBR material and its sound absorption performance were explored.The main findings are as follows:The first part(Chapter 3)of this paper studies the co-vulcanization and processing technology of EUG and SBR.By analyzing the vulcanization characteristics,physical and mechanical properties,peel strength and dynamic mechanical properties of rubber composites with different formulations of EUG and SBR,it was found that when the vulcanization system was used—accelerator DZ 1.0,accelerator TMTD 0.1,and sulfur 1.5,The co-vulcanization effect of EUG and SBR is better,the peel strength of the two rubbers is 4.2 k N/m,and the tensile strength of the composite is 6.3 MPa,which can be attributed to the formation of more sulfur crosslinks between EUG and SBR.The physical and mechanical properties,dynamic mechanical properties,microscopic phase state and crystallization properties of the composites prepared by four processing techniques were characterized.The research results found that when the internal mixer was used for mixing,with the increase of shear time,the EUG viscosity decreased,so The EUG crystal region becomes smaller in the prepared composite material.After adjusting the mixing parameters,the optimal mixing process of EUG/SBR rubber composites with internal mixer and open mixer was obtained.In the second part(chapter 4)of this paper,rubber composites with different ratios of EUG and SBR were prepared,and the microphase state,crystallization properties,dynamic mechanical properties and physical and mechanical properties of the composites were systematically analyzed.The results show that the EUG distribution in the composites is uniform and all are sea-island structures.With the increase of EUG,the glass transition temperature(T_g)of the composites decreased from-45.7℃to-48.3℃,indicating good compatibility between the two.In the range of-20～40℃,the storage modulus of the composites increased significantly.At 10℃,its storage modulus will increase from 3.0×10~6Pa to 1.7×10~7Pa,which is because the addition of EUG limits the deformation ability of rubber macromolecules and realizes the cross-scale regulation of the storage modulus of composite materials..When the EUG content is less than 20 phr,the tensile strength of the rubber composite increases slowly.When the EUG content reaches 20 phr and above,the tensile strength and tensile stress of the composite begin to sharply increase,and when the EUG content reaches 40phr,the composite reaches a tensile strength of 11.0 MPa(equivalent to 5times that of pure SBR),the infiltration phenomenon of EUG crystal region-enhanced SBR appears.This phenomenon provides a new idea for analyzing the structure and properties of EUG composites.The third part(chapter 5)of this paper investigates the effect of EUG content on the vulcanization characteristics,thermal properties,crystallization properties,dynamic mechanical properties,physico-mechanical properties and acoustic properties of EUG/SBR/CB rubber nanocomposites.The results show that EUG exists in the form ofβ-type crystal in the composite material.Between-20 and 40°C,the storage modulus gradually increases.At 10℃,the storage modulus increased from 7.6×10~6Pa to 3.6×10~7Pa,and the addition of carbon black further improved the storage modulus of the composites.The tensile strength increased from 15.2 MPa to 22.6 MPa,an increase of 47%.The 100%tensile stress increased from 1.0 MPa to 3.9 MPa,an increase of nearly 2 times.Carbon black and EUG crystals can jointly improve the mechanical strength of rubber nanocomposites.At frequencies between 8 and15 k Hz,the average sound absorption coefficient of EUG/SBR/CB rubber nanocomposites is higher than that of SBR/CB rubber nanocomposites at all pressure points.At 0.5 MPa and 3.0 MPa,the average sound absorption coefficients of EUG/SBR/CB=30/70/30 rubber nanocomposites are 0.98 and0.90,respectively,which are higher than 0.85 and 0.80 of SBR/CB rubber nanocomposites.At the same time,the average sound absorption coefficient of SBR/CB rubber nanocomposites under different pressures is the highest of0.96 and the lowest of 0.80,with a large fluctuation range.The average sound absorption coefficient of EUG/SBR/CB(30/70/30)rubber composites under different pressures is the highest of 0.99 and the lowest of 0.93,showing stable sound absorption performance under different pressures.The results show that this material has excellent sound absorption performance under high net water pressure. |
