Two Dimensional Nanomaterials/Rubber Composites:Preparation,Structure And Performance

2D nanomaterials are sheet-like structures with single-or few-layer thickness,but lateral size larger than 100 nm or even up to tens of micrometres.Owing to the ultrahigh specific surface area and strong quantum confinement of electrons in two dimensions,these 2D nanomaterials display many unconventional physical,optical,chemical and electronic properties.As nanofiller for polymer,2D nanomaterials have exceptional reinforcing efficiency towards polymer matrix,and they can endow the composites with functional properties.They also exhibit broad application prospects in rubber composite materials.Discreteness of the lateral size of graphene prepared by oxidation is relative large,but the influence of the lateral size of graphene on the properties of rubber is still unclear.Hexagonal boron nitride nanosheets(BNNSs),isoelectric analogous to the graphene,exhibit very high thermal conductivity but electrically insulation.However,the real-life applications of BNNSs in elastomer composites are greatly limited by the large-scale production,the preparation methods for elastomer/BNNSs composites,the modification of BNNSs,the design of interfacial structures.Accordingly,in the present dissertation,we focused on the studies of the BNNSs and elastomer/ BNNSs composites.(1)In order to analyze the influence of the lateral size of graphene oxide(GO)on the properties of natural rubber/graphene oxide(NR/GO)nanocomposites,three different sized graphene oxide sheets,namely G1,G2 and G3 were used to fabricate a series of NR/GO nanocomposites by latex mixing.The results indicate that adding GO can remarkably increase the modulus of NR.The enhancement of modulus is strongly dependent on the size of GO sheets incorporated.G1 with smallest sheet size gives the maximum reinforcement effect compared with G2 and G3.Dynamic mechanical measurement and swelling ratios indicate that G1 has stronger interfacial interaction with NR.XRD shows G1 is more effective in accelerating the strain-induced crystallization(SIC)of NR.The strong interfacial interaction facilitates the stress transfer and strain-induced crystallization,both of which lead to the improved modulus.(2)So far,most of the preparation methods for polymer/boron nitride nanosheets(BNNSs)composites are not suitable for mass production.Surry compounding may solve this problem.BNNSs aqueous dispersion was prepared by sonication and then the water in BNNSs suspension was exchanged by volatile ethanol.BNNSs slurry with a high concentration about 50 mg/m L was obtained.The slurry was then compounded with styrene-butadiene rubber(SBR)to form the rubber/BNNSs composites via conventional two-roll milling.The solvent in the slurry prevented the aggregation of BNNSs and promoted the dispersion of BNNSs in rubber matrix.The sulfide-containing silane was introduced to modify the interface between BNNSs and the rubber.The silane modified BNNSs(Si-BNNSs)has been characterized by FTIR,XPS and TGA.The differences of interfacial interactions in the systems were confirmed by SEM,the equilibrium swelling experiment,Mooney Rivlin curve,Nint equation.It is found that,with in situ modification of the silane,the rubber/BNNSs composites exhibited significantly improved thermal conductivity.Meanwhile,the mechanical properties of the composites are simultaneously largely enhanced.The improved dispersion of BNNSs and interfacial interactions facilitate the ultimate performance of the composites.The scalable yet environmentally-friendly slurry approach paves the way for industrial-scale utilization of BNNSs in thermally conductive polymer composites.(3)A facile and green approach for fabricating polyrhodanine coated BNNSs nanostructure in aqueous solution was reported.The successful coating of polyrhodanine onto the surface of BNNSs has been confirmed by TEM,DRIFT,UV-Vis spectra,TG and XPS,etc.The introduction of polyrhodanine effectively improved the interfacial interactions between BNNSs and the rubber matrix by forming interfacial crosslink.The significant improvement in the interfacial interactions between the SBR matrix and PRh-BNNSs is confirmed by equilibrium swelling experiments,freezing point depression,surface energy and SEM.Accordingly,the SBR/PRh-BNNSs composites exhibited unique combination of high mechanical properties and high thermal conductivity.Importantly,the orientation of BNNSs in the elastomer led to further increase in thermal conductivity.Overall,the present work offers a new route for the design of thermally conductive elastomers through the combination of efficient interfacial modification and filler organization.(4)Elastomer chains were first mechanochemical grafted onto the polyrhodanine coated BNNSs by two-roll milling and then an ultra-flexible,highly thermal conductive and electrical insulating paper based on BNNSs was fabricated by vacuum filtration.The mechanochemical grafting of XNBR chains onto polyrhodanine coating during shear mixing was demonstrated by FTIR,NMR,AFM,TEM and TG.The grafted elastomer chains act as mortar to link the BNNSs bricks together,forming a highly oriented layer structure.In addition,by controlling the content of grafted rubber chains,a flexible and electrical insulating paper with an in-plane thermal conductivity of up to 45.7 Wm-1K-1 is achieved,which is much higher than most of the reported BN-based composites or films.