Synthesis Of Functional Ethylene Propylene Rubber/SiO₂ Composites

Ethylene propylene rubber（ethylene-propylene copolymer,EPR）is one of the most important commercial synthetic rubbers.Due to the insufficient rigidity of ethylene propylene rubber,the reinforcement of ethylene propylene rubber by filling inorganic fillers（such as carbon black,silica and fillers with nanostructures）or renewable resources is indispensable for practical applications.Silica（SiO₂）is the most widely used light-colored reinforcing filler in the rubber industry and has received extensive attention due to its high tear strength,excellent aging resistance and less heat build-up.However,the main disadvantage of silica is the tendency of gathering due to the strong hydrogen bonding interaction between the hydroxyl groups on the surface of the particles.Furthermore,the polarity of the silica surface makes it difficult to be compatible with inert EPR.In this paper,a functional ethylene-propylene rubber with a silica-chloride bond in the side chain was designed and synthesized,then the toluene dispersion of silica was directly added to the polymerization gel.After that,the chemical linkage of the polymer molecular chain and silica was realized in situ polymerization in the reactor,and the preparation of ethylene-propylene rubber/SiO₂ composites material was achieved.The conclusions are as follows:（1）By synthesizing and comparing a series of functional olefin monomers containing a silicon-chloride bond,the copolymerization activity,monomer insertion rate,monomer conversion rate,etc.of the functional monomer are studied in detail,and5-（trichlorosilyl）-2-norbornene was selected to carry out the synthesis of ethylene-propylene rubber.Its ethylene-propylene terpolymerization activity under the catalysis of metallocene catalyst rac-Et（ind）₂ZrCl₂ can reach 10⁶ g EPDM/（mol Zr·h·atm）;the insertion rate of functional monomer can be Adjusted between 0.71 and 4.68 mol%,which means that the number of silicon-chloride bonds in each polymer chain can be adjusted between 10 and 74.（2）By the in-situ composite method,the toluene dispersion of SiO₂ was directly add to the above polymerization gel.The reaction effect of the silicon-chloride bond of the ethylene-propylene rubber side group and the silanol group on the surface of SiO₂ was investigated.By adjusting the concentration of SiO₂ toluene dispersion,a series of composite materials with different SiO₂ content were prepared.The SiO₂ content can be controlled in the range of 13⁸5wt%.（3）The composition,microstructure and mechanical properties of the above-mentioned ethylene-propylene rubber/SiO₂ composites synthesized by in-situ polymerization were studied in detail,and compared with the composite materials prepared by traditional blending methods;FITR test results and TGA analysis results showed that the molecular chain of SiO₂ and ethylene-propylene rubber in the composite material was connected by covalent bond;morphological analysis methods SEM and TEM were used to observe the dispersion level of SiO₂ in the composite material,and RPA test method was selected to observe the dispersion stability.And these results showed that the above properties of the composite prepared by the method we used are superior to those physical blending materials;the mechanical properties of the composites were further determined by DMA,stretching test,etc.and the results were also significantly better than the composite materials prepared by physical blending.