Preparation And Properties Research Of Porous Magnetorheological Rubber

Magnetorheological elastomers(MREs)are a branch of magnetorheological materials,which are intelligent polymer composites composed of micro-sized soft magnetic particles dispersed in viscoelastic polymer matrix.The intelligent characteristic of these materials is that the dynamic and static mechanical properties can be changed continuously,reversibly and rapidly by an external magnetic field.It has be widely applied in damping shock absorbers,shape memory materials,sensors and so on.However,the magnetorheological and mechanical properties of MERs cannot be combined at the same time,which limits their application.At present,the research on MERs mostly focuses on the modification of the matrix and magnetic particles,and there are few reports on the preparation of high-performance magnetorheological elastomers by structural design of the matrix of MERs.In view of the fact that porous elastomers have the charactetistics of light weight,large specific surface area and good damping performance,the magnetic porous structure matrix is taken as the structural design target in this paper to prepare magnetorheological elastomers with high relative magnetorheological effect,good damping performance and strong mechanical properties.By in-situ synthesis of chemical foaming reaction and cross-linking reaction,non-magnetic natural rubber porous elastomer with low density,high resilience and strong mechanical properties as the matrix of magnetorheological elastomer was prepared with natural rubber with excellent comprehensive properties.This natural rubber porous elastomer is used as the matrix of subsequent magnetorheological elastomer.Then,on the basis of it,the soft magnetic material CI with high magnetic saturation strength is used as magnetic particles,and the porous magnetorheological elastomer with better relative magnetorheological effect,good damping performance and outstanding mechanical properties is prepared by in-situ synthesis in one step.Adding graphene oxide as reinforcement to optimize the porous structure.Then,the porous magnetorheological elastomer was used as the"skeleton"and the magnetorheological plasticity was filled into the three-dimensional"skeleton"to prepare the magnetorheological composites with high relative magnetorheological effect,good damping performance and excellent mechanical properties.The main experimental contents and research results are listed as follows:(1)The effects of the amount of blowing agent H on the morphology and static mechanical properties of porous elastomers based on natural rubber were studied.The experimental results show that optimum dosage of foaming agent H is 4 phr.When content of H is 4 phr,t he pores oft he porous rubber elastomer exhibited a network distribution state of closed pores.The pore size is uniform(0.68±0.007μm),th e defe ct of the pore wall is less,and the morphology of the porous rubber elastomer is the most excellent.Its rebound rate is up to 95.5%,tensile strength is 1.82 MPa,elongation at break is 468.7%.The apparent density and porosity of the porous elastomer are 0.39 g/cm~3a nd 64%,respectively.I n addition,the chemical foaming process is carried out at the same time as the rubber vulcanization process.This"one-step"process is simple,time-saving and suitable for industrial production.(2)The effect of CI content on the microstructures,dynamic and static mechanical properties of porous magnetorheological elastomers was studied by choosing 4 p hr blowing agent and using CI as magnetic particle under the same preparation process.The results show that when CI content is 180 phr,the microscopic morphology,rebound rate and dynamic mechanical properties of porous MERF are optimal.The pore size of porous elastomer is 0.48±0.006μm.Compared withth en on-magneticna turalru bberm atrix,the pore size of porous elastomer is smaller and the homogeneity.The relative magnetorheological effect,tensile strength and elongation at break of porous elastomer is464.3%,4.62 MPa and 300.5%,respectively.It shows that the relative magnetorheological effect and excellent mechanical properties are taken into account.In addition,it has been found that this material has excellent magnetostrictive properties,and the deformation amount can reach 11%at a magnetic field strength of 1 T.(3)In view of the good compatibility between graphene oxide and natural rubber matrix,graphene oxide is used as a functional filler to improve the hole-breaking phenomenon of porous magnetorheological elastomer.The effects of graphene oxide content on the morphology,dynamic and static mechanical properties of porous magnetorheological elastomers were studied.When GO dosage is 0.8 phr,the integrity of the hole wall is the best,and the rebound rate is increased to the maximum,up to 97.2%.The tensile properties and elongation at break are up to 5.02 MPa and 181.6%respectively.Meanwhile,the relative magnetorheological effect is up to 422%.GO plays the role of matrix reinforcement phase.It shows that the mechanical properties are greatly improved by adding appropriate GO,while the relative magnetorheological effect of MREFG are good.(4)The CI/PDMS magnetorheological plastomer was used as the filling body,and the porous magnetorheological rubber with open-cell structure was used as the three-dimensional pore skeleton.The CI/PDMS magnetorheological plastomer/porous magnetorheological rubber composite was synthesized by capillary action.The effect of magnetorheological plastomer on the microstructure and dynamic and static mechanical properties of composite magnetorheological rhbber was studied.The relative magnetorheological effect of composite magnetorheological materials(MREFP)reaches1483.3%,which was 216.3%higher than MREF.At the same time,the tensile mechanical strength of the composite magnetorheological material was 1.83 MPa,and the tensile strength of the porous magnetorheological rubber without the magnetorheological plastomer was 1.78 MPa.The tensile strength of(MREFP)was 2.8%higher than MREF.In addition,the loss factor is increased from 0.48 to 0.74 for MREFP.The introduction of magnetorheological plasticity composite magnetorheological material takes into account the high relative magnetorheological effect of magnetorheological plasticity and the good mechanical properties of porous magnetorheological elastomer.This structural design concept of filling magnetic materials into magnetic"skeleton"provides a new idea for the preparation of new high-performance magnetorheological materials in the future.