Sodium Humate-functionalized Graphene And Its Reinforcement For Rubber

Graphene is a kind of two-dimensional planar crystal structure carbon materials withexcellent mechanical properties, electrical conductivity, thermal conductivity and opticalproperties. Since its discovery in2004, it has drawn numerous attentions in the focus ofexperimental and theoretical studies from scientists all over the world, because of its superiorproperties and a wide range of applications in the electronic, thermal conductive materials,damping materials, polymer composites, biological medical instrument materials and manyother potential applications.In this thesis, we succeed in fabricating sodium humate-functional graphene (NaA-GE),with the graphene oxide (GO) as the precursor, which is prepared by a modified Hummersmethod. The humic acid (HA) is a kind of environmentally non-toxic, cheap and easilyavailable natural substance. We converted it into sodium humate (NaA) by reacting withsodium hydroxide and used the resulted NaA to non-covalently decorate graphene. Evidencedby the result of atomic force microscope (AFM), the individually dispersed NaA-GE in waterwas revealed. The NaA-GE colloid could remain stable with a high concentration of30mg/ml.The results from FTIR, UV and Raman spectroscopy substantiated that π-π interactions andhydrogen bonding were the main interaction mechanisms between NaA and graphene lamella.The XNBR/NaA-GE and XNBR/GO nanocomposites was fabricated through a process ofemulsion coagulation method. Dual vulcanization system with zinc oxide and sulfur wasutilized. High quality dispersion of NaA-GE and GO in the matrix was substantiated by theresults of FESEM and XRD. When NaA-GE content was only7phr, the tensile strength and100%modulus of XNBR/NaA-GE composite were increased by76%and310%, respectively.In the GO reinforced XNBR composites, when GO content was5phr, the tensile strength and100%modulus were increased by33%and359%, respectively. These results clearlydemonstrated the significant reinforcing efficiency of GO and NaA-GE towards XNBR.In the ZnO/S cured systems, due to the excessive curing reactivity, the generated ionicclusters may be not uniformly dispersed. Therefore, MgO was used to replace ZnO and theMgO/S cured XNBR and the composites were prepared. The results from FESEM, TEM andXRD confirmed that, at relatively low content of NaA-GE, the graphene layers were found to be dispersed individually in the matrix. With the incorporation of5phr of NaA-GE, thetensile strength, tear strength,100%modulus of XNBR/NaA-GE composite were increasedby120%,64%and129%, respectively. In addition, the increasing of graphene content did notdeteriorate the elongation at break. When the reinforcement was GO, the ZnO/S curedsystems possessed much higher modulus, but lower tensile strength. When the reinforcementwas NaA-GE, the MgO/S cured samples had higher tensile strength and the divergence inmechanical data was smaller than that for the ZnO/S cured systems. The incorporation ofNaA-GE could remarkably reduce the gas permeability. Due to the excellent abrasionresistance of the neat XNBR, the improvement in the abrasion resistance of the compositeswere not significant.