Preparation For Graphene Oxide And Its Modification Study On Polyurethane Materials

In China, the graphite mineral resources are rich and excellent, and have the largestyields and exports in the world. However, the deep processing technology of graphite fallsbehind. The research and development efforts for improving the added values of graphiteproducts are extremely urgent. The graphene has many excellent properties of both graphiteand carbon nanotubes, expected to be a new high-performance nano-enhanced body toimprove the performance of polymer composites, thus expanding their application areas.Using the graphite to prepare graphene oxide sheets (GOs) is considered to be the strategicpoint of producing graphene on a large-scale. The graphene oxide has the advantages ofhigher specific surface energy, good hydrophilic and mechanical properties, yet ownsexcellent reflection and absorption abilities to the light and radiation. Besides, the grapheneoxide can be well dispersed in water and some other polar organic solvents, and mostimportantly the cost is much lower than carbon nanotubes. Taking the graphene oxide asfillers to blend in polyurethane (PU) can conbine the advantages of graphene oxide withpolyurthane. It can not only endow the composite materials with excellent mechanicalproperties, thermal properties, permeability and anti-aging properties, but also give thecomposites special antibacterial functions, optical performance and electrical properties.In this thesis, the graphite oxide was prepared from natural flake graphite by themodified Hummers method, and then the GOs were obtained with the help of ultrasonicstripping. The samples were characterized by using UV-vis, SEM, TEM, AFM, Raman,FT-IR and XRD. The results showed that the GOs were prepared with good stability andvarious oxygen bearing functional groups (C=O,-OH,-COOH and C-O-C). Then the GOswere added to the ready water-based polyurethane (WPU) by solution co-blending. Themechanical property, water resistant, electrical conductivity, thermal stability and agingresistance of GOs/WPU composites were researched. The results showed that: compared tothe unmodified pure WPU film, the tensile strength of GOs/WPU co-blending membranessignificantly improved, and when the additive amount of GOs reached0.6wt﹪, themechanical properties of the blend membranes were best and the tensile strength was twice asthat of the pure WPU film. However, with the contents of GOs incresing, the elongation atbreak decreased slowly; GOs can significantly improve the UV-aging resistance properties of the WPU films, while0.6wt﹪GOs were added, the anti-aging properties and waterresistance performance of GOs/WPU co-blending membranes arrived the best; Furthermore,the thermal stability of the WPU was obviously improved, and the thermal decompositiontemperature of the composites containing0.6wt﹪GOs increased by nearly30℃.The wet polyurethane microporous membranes modified with the GOs, acidulatedcarbon nanotubes and carbon nanotubes (CNTs) were prepared, and the effects of additiveamounts of GOs on the mechanical properties, electrical behavior, permeability and agingresistance of as-prepared PU microporous membranes were investigated by means of tensiletest and megger equipment. The results showed that: when the additive amount of GOsreached0.1wt﹪, the dispersion was best and the mechanical property of the PU microporousmembrane was significantly improved, and the tensile strength was twice as that of the purePU microporous membrane; with increasing the content of GOs, acidulated CNTs and CNTs,the rate of moisture absorption, porosity and permeability of moisture of the functionalmicroporous membranes were improved to some extent in our experiments, it was noted thatthe permeability of GOs modified microporous membranes improved most significantly. ThePU microporous membrane containing1.0wt﹪GOs had the highest moisture absorptionrate, porosity and permeability compared with the pure PU microporous membrane, and therate of moisture absorption, porosity and permeability of moisture were increased by466.4﹪,153.4﹪and153.5﹪respectively. In addition, while0.1wt﹪GOs were added, highpermeability of the microporous membrane was obtained and good mechanical propertieswere maintained at the same time. GOs could significantly improve the aging resistanceproperties of PU microporous membranes, while GOs content reached to0.1wt﹪, the agingresistance of the microporous membrane was the most outstanding. Besides, GOs had noeffect on the conductive properties of WPU films and PU microporous membranes, as GOswere non-conductive, only when GOs were reduced to the graphene, the investigation on theconductivity of the modified polyurethane materials made sense. In general, the performanceimprovements of GOs modified polyurethane materials were the most significant, followedby the acidulated CNTs,and CNTs were the worstwhich couldn’t play the positive role.Leather finishing applications experiments showed that: GOs could significantlyimprove the abrasion resistance performance of the finishing leather to some extent; theleather samples finished by the purchased WPU and GOs modified WPU owned some folding fastness, and dry-erase resistance level all reached to4.5degrade. The folding fastness ofGOs modified leather coatings were better than the unmodified leather coat, except the leathersample containing1.0wt﹪GOs. Furthermore, when the GOs content less than or equal to0.6wt﹪, the moisture rub degrade of the modified coatings could arrive at4.0/3.5, muchbetter than the unmodified WPU coating.