Preparation And Performance Improvement Mechanism Of Modified Damping Rubber Composite

Natural rubber（NR）has good elasticity,mechanical properties and processing properties,and is widely used in the manufacturing industry of damping rubber bearings.However,its narrow effective damping temperature range is not conducive to the development of NR’s excellent properties,and it cannot meet the requirements of practical applications for high-performance damping and isolation materials.It is necessary to broaden the effective damping temperature range and improve the service performance of products by modification.In this thesis,NR/AO-80,NR/AO-80/SIS and NR/AO-80/SIS/ENR modified rubber composites were prepared by using hindered phenolic polar small molecule（AO-80）to modify NR,and then mixed with styrene isoprene block copolymer（SIS）and epoxidation natural rubber（ENR-25）.The microstructure of rubber materials was characterized by Fourier infrared spectroscopy（FTIR）,X-ray diffraction（XRD）and scanning electron microscopy（SEM）.The glass transition temperature（Tg）,mechanical properties,damping properties and vulcanization characteristics of rubber were analyzed by differential scanning calorimeter（DSC）,universal testing machine,dynamic thermomechanical analyzer（DMA）and rotorless rheometer.The compatibility between NR/AO-80 and NR/AO-80/SIS phases,molecular interaction mechanism and molecular chain structure characteristics were simulated by molecular dynamics simulation（MD）.NR,NR/AO-80,NR/AO-80/SIS and NR/AO-80/SIS/ENR were selected as the base rubber to make the vibration isolation bearing.The vertical compression and horizontal shear properties of the bearing were tested to investigate the practicability of the bearing.The main research contents and results are as follows:（1）The compatibility and intermolecular force of NR/AO-80 were simulated,and it was predicted that AO-80 and NR had good compatibility and strong intermolecular force when the content of AO-80 was 15 wt%,which could be used to guide the formulation design of NR/AO-80 compound.DSC analysis showed that AO-80 could increase the glass transition temperature of NR.The results of FTIR and XRD analysis showed that AO-80 existed in the NR matrix in an amorphous state,and the interaction between the molecular chain of NR and AO-80 was strong.When the mass ratio of NR to AO-80 is 100:15,the elongation at break of NR/AO-80 increases from 536.1%to 617%.The tanδ_maxof NR/AO-80 increased from 0.11to 0.35,which was more than two times higher than that of NR,and the effective damping temperature range increased from 25.17°C to 31.25°C.However,the results also showed that tanδmax decreased significantly in the low temperature region of NR/AO-80,and the damping performance of the low temperature region should be further improved.（2）In order to further improve the damping performance of NR/AO-80 and broaden its effective damping temperature range,styrene isoprene block copolymer（SIS）was introduced into NR/AO-80 system,and the influence of SIS on the damping performance of NR/AO-80 system was investigated.The results showed that when the SIS content exceeded 16 wt%,the phase separation between SIS and NR/AO-80 gradually appeared,and effective phase separation was helpful to broaden the damping temperature range of rubber materials.After high temperature aging,the tensile strength and elongation at break of NR/AO-80/SIS only decreased slightly,indicating that NR/AO-80/SIS had good aging resistance.The tanδmax of NR/AO-80/SIS can reach 0.95,which is 25%higher than that of NR/AO-80.tanδ_maxincreases from 0.1 to 0.37 at room temperature,which is two times higher than that of NR/AO-80.The effective damping temperature range of NR/AO-80 was widened from25.2°C to 114.5°C,which was 43.4°C higher than that of NR/AO-80,indicating that SIS could significantly broaden the effective damping temperature range of NR/AO-80 and improve its damping performance at service temperature.Molecular dynamics simulation was used to quantitatively analyze the relaxation behavior of NR molecular chains,and the mechanism of SIS improving the damping performance of NR/AO-80 was explored.It was shown that the van der Waals forces between molecules of the composite materials were significantly enhanced with appropriate SIS,which promoted the energy dissipation of NR/AO-80/SIS,and SIS provided more physical cross-linking points.The energy dissipation and internal friction are enhanced.The results of mechanism analysis agree with the experimental results.（3）In order to improve the dispersibility of SIS in NR/AO-80 matrix,epoxy natural rubber（ENR-25）was introduced into NR/AO-80/SIS compound to further improve the damping performance of NR/AO-80/SIS and broaden its effective damping temperature range.The results showed that the dispersability of SIS in NR/AO-80 matrix could be effectively improved with appropriate ENR.When the mass ratio of m NR:m ENR was 85:15,the curing process of NR/AO-80/SIS/ENR was accelerated and the processing safety was improved.The maximum tensile strength and elongation at break of NR/AO-80/SIS/ENR were 25.8 MPa and 785.3%respectively,which were 6.2%and 8.8%higher than those of NR/AO-80/SIS system.After high temperature aging,the tensile strength and elongation at break of NR/AO-80/SIS increased by 5.4%and 7.7%compared with those without ENR compound.The tanδ_maxof NR/AO-80/SIS/ENR at low temperature increased by 49.5%compared with NR/AO-80/SIS,and that of room temperature increased by 5.4%compared with NR/AO-80/SIS.The effective damping temperature range was widened from 116.58°C to 137.04°C,which increased by 20.46°C,indicating that ENR can further improve the damping performance in the low temperature zone and room temperature zone.（4）NR,NR/AO-80,NR/AO-80/SIS and NR/AO-80/SIS/ENR damping rubber composite materials were used as rubber base to prepare the damping and isolation bearing,and the strength and damping performance of the bearing were tested.The vertical compression stiffness and horizontal equivalent stiffness of the bearing with appropriate NR/AO-80/SIS/ENR can be up to 977.9 k N/mm,the equivalent damping ratio can be up to 1.38 k N/mm,and the equivalent damping ratio is 17.2%,and the theoretical error of the corresponding data is not more than 10%.The results show that the NR/AO-80/SIS/ENR bearing has strong mechanical properties and excellent equivalent damping ratio,which indicates that the synthesized NR/AO-80/SIS/ENR has good damping and isolation effect and practical application potential.