Functionalized Modification Of Graphene Oxide And Its Application In Rubber

Graphene（GE）has outstanding thermal conductivity,electrical conductivity and mechanical properties compared to other nano fillers,and is widely used in the field of rubber modification research.However,due to the lack of active groups and functional on the surface of graphene,and due to the conjugation effect and van der Waals force between graphene sheets,graphene was found to exhibit poor dispersion in the rubber matrix,which greatly reduced the modification effect;it was not possible to maximize the excellent performance of graphene itself.In order to fully utilize the modification effect of graphene on rubber,it is necessary to functionalize it.Therefore,in recent years,the research on the functional modification of graphene and its application in rubber composites has increasingly attracted the attention of scientists and technicians from various countries,and has become a hot topic in this field.The paper aims to improve the dispersion uniformity of graphene fillers in rubber based materials and maximize the reinforcement effect of graphene on the rubber matrix,three polymer modified microspheres were designed and synthesized based on three different rubber systems（NBR,NR/SBR,SBR/NBR）in the paper:PAN microspheres,cationic PS microspheres,and P（An-St）copolymer microspheres,which were used for graphene modification.Three functionalized graphene oxide materials modified by polymer microspheres were obtained:rGO-PAN,rGO-PS and rGO-P（An-St）.Then three kinds of functionalized graphene oxide were blended with the corresponding rubber latex to prepare the master rubber.Finally,the master rubber was added to NBR,NR/SBR and SBR/NBR respectively to obtain three kinds of rubber composites modified by functionalized graphene oxide:rGO-PAN/NBR,rGO-PS/NR/SBR,rGO-P（St An）/SBR/NBR.At the same time,in order to compare,three rubber composites with graphene directly added to rubber（rubber blend）were prepared:rGO/NBR,rGO/NR/SBR and rGO/NBR/SBR.For PAN microspheres modified system:The electron microscope measurement results showed that the PAN microsphere particles with a particle size of about 200-300 nm were embedded in clusters or tightly adsorbed between the sheets of reduced graphene oxide,effectively separating the sheets of graphene oxide,thereby avoiding the agglomeration of GO due to the strong non covalent bond force between the sheets.The functionalized graphene oxide rGO-PAN modified by PAN microspheres dispersed uniformly in the rubber matrix,presenting irregular spherical protrusions and blurring the phase interface with NBR,indicating that the modified graphene had a good dispersibility in the rubber.The thermal performance test results of rGO-PAN/NBR showed that with the increase of rGO-PAN filler content,the thermal decomposition temperature of 5%did not change significantly,but the maximum thermal decomposition temperature(Td _MAX)had a significant increase.When the filler content of rGO-PAN was 2.0wt%,the Td_MAX of the composite material rGO-PAN/NBR increases by 23.71℃compared to pure nitrile rubber;The mechanical performance test results show that when the addition amount of rGO-PAN is 1.2wt%,the tensile strength and 300%constant elongation stress of the composite material are 4.79 MPa and 2.79 MPa,respectively,which are the maximum values of the same group,and were increased by 53.0%and 50.8%compared to pure nitrile rubber,respectively.Compared with rGO/PAN composites with the same amount of graphene,the tensile strength and 300%constant elongation stress of rGO-PAN/NBR composites increased by 11.5%and 6.3%,respectively.For cationic PS microspheres modified system:The electron microscope test results showed that PS microspheres with a particle size of about 250-300 nm were embedded in clusters between the layers of graphene oxide,forming a well-defined intercalation structure,avoiding the stacking and agglomeration of graphene due to strong non covalent bond forces between the layers.The functionalized graphene oxide rGO-PS modified by cationic PS microspheres was uniformly dispersed in NR/SBR blend without obvious agglomeration.In addition,rGO-PS was found to exhibit irregular spherical protrusions in the matrix of the blend and the phase interface between rGO-PS and the NR/SBR blend was fuzzy,indicating that the interfacial compatibility between rGO-PS and the NR/SBR matrix had been improved.The thermal performance test results of composite material rGO-PS/NR/SBR show that with the increase of rGO-PS content,the thermal decomposition temperature(Td_5%)and maximum thermal decomposition temperature(Td _MAX)of rGO-PS/NR/SBR are significantly improved,with Td_5%and Td _MAX increased by nearly 20℃and 30℃,respectively.The mechanical property measurement results showed that when the addition amount of rGO-PS was 1.6wt%,the tensile strength and 300%constant elongation stress of the composite rGO-PS/NR/SBR reached their maximum values,The tensile strength and300%constant elongation stress of the composite material rGO-PS/NR/SBR are 3.10MPa and 2.64MPa,respectively,which are the highest values in the same group.Compared with pure NR/SBR blends,they have increased by 19.8%and 25.7%,respectively.Compared with composite material rGO/NR/SBR,the tensile strength and 300%constant elongation stress of rGO-PS/NR/SBR increased by 5.8%and 2.3%,respectively.For P（An-St）copolymer microspheres modified system:The electron microscope test results showed that P（An-St）copolymer microspheres with a particle size of 100-200 nm were orderly intercalated and adsorbed between the layers of graphene in a grape string shape,forming a clear intercalation structure,effectively avoiding the aggregation of GO due to the strong non covalent bond force between the layers.The rGO-P（An-St）modified by P（An-St）copolymer microspheres dispersed uniformly in the rubber matrix,presenting irregular spherical protrusions,without significant phase interfaces or phase separation,indicating that the modified graphene exhibited good dispersion in the rubber.The vulcanization performance curve of the composite rGO-P（An-St）/SBR/NBR showed that with the increase of the amount of rGO-P（An-St）,the initial vulcanization time T10 did not change significantly,but the positive vulcanization time T90 and the minimum torque ML showed a gradual upward trend.The mechanical property measurement results showed that when the addition amount of rGO-P（An-St）was 1.6wt%,the tensile strength and 300%constant elongation stress of the composite rGO-P（An-St）/SBR/NBR reached their maximum values,which were increased by about 109.3%and 75.2%compared to the pure blend SBR/NBR,respectively.Compared with the composite material rGO/NBR/SBR with the same amount of graphene,the tensile strength and 300%constant elongation stress of rGO-P（An-St）/SBR/NBR increased by 0.9%and 9.0%,respectively.