Synthesis Of Isocvanate Modified Graphene And Its Appolication For Conductive Coatings

Waterborne polyurethane was prepared with water as solvent. With the characteristics suchas safety and environmental protection, good filming, strong flexibility, high abrasion andsolvent resistance, the waterborne polyurethane was used as a common coated fabric finishingagent. The introductions of hydrophilic groups in the process of the waterborne polyurethanepreparation lead to poor water resistance and poor electrical conductivity of of the fabrics coatedby waterborne polyurethane, and these defects make the application of waterborne polyurethanewas restricted. As graphene being a new type of carbon materials, had excellent electricalconductivity and water repellency, it was an effective method to use graphene to modifywaterborne polyurethane for elevating antistatic ability and water repellency of the waterbornepolyurethane. However, the dispersibility of graphene in solvents and polymer matrix was poor,and the poor graphene dispersion in the waterborne polyurethane film cannot fully embody itsexcellent performance. The functional modification of the graphene could greatly improve itsdispersion in waterborne polyurethane film, and make the hydrophobic property and antistaticability of graphene in the waterborne polyurethane film play very well. In view of this, theisocyanate modified graphene was synthesized to modify waterborne polyurethane, and theIMG/polyurethane was applied to coat the polyester fabric. The research contents of this paperwere divided into three parts.Part one: Synthesis and characterization of graphene and isocyanate modified graphene. Thegraphene and isocyanate modified graphene (IMG) were prepared with natural graphite as rawmaterial, concentrated H2SO4and KMnO4as oxidizer, isophorone diisocyanate as functionalmodifier, and hydrazine hydrate as reductant. The influences of reduction temperature, thereduction time and the dosage of reductant on removing the oxygenic groups were discussed, andthe reduction reaction conditions were optimized. The chemical structures of the products werecharacterized by FTIR, XRD, element analyzer and XPS, and the thermal stability and dispersionof the functionalized graphene in solvents DMF were also studied. The results showed that theoptimal reduction conditions were that the reaction temperature was95℃, and reaction time was100min, the mass ratio of reductant and graphite oxdie was1:1. The structure of graphene andIMG were characterized by FTIR, XRD, and element analyzer and XPS. Compared with that of graphene, the thermal stability of the isocyanate modified graphene reduced, but the dispersity ofisocyanate modified graphene in DMF was improved significantly.Part two: Study on preparation of isocyanate modified graphene/waterborne polyurethaneand its properties. The IMG/waterborne polyurethane emulsion was prepared by mixing up IMGwith waterborne polyurethane through the ultrasonic dispersion method. The dispersity of theIMG in waterborne polyurethane film was investigated, and the influences of dosages of IMG onthe properties of emulsion and its film were studied. The results showed that IMG could bedispersed well in waterborne polyurethane film. As the dosage of IMG increased, the particlesize of the IMG/waterborne polyurethane emulsion increased, the electrical resistivity of theIMG/waterborne polyurethane film decreased, the water contact angle of the IMG/waterbornepolyurethane film increased, the tensile strength of the IMG/waterborne polyurethane filmincreased and its elongation at break decreased. The thermal stability of the IMG/waterbornepolyurethane film was also improved. The results showed that electrical conductivity and waterresistant of the waterborne polyurethane film were improved after mixing with IMG, and both ofelectrical conductivity and water resistant of the film had good performance.Part three: Study on application of isocyanate modified graphene/waterborne polyurethane.The self-made isocyanate modified graphene/waterborne polyurethane was applied in coating ofpolyester fabric, the influences of dosages of IMG on electrical conductivity, water contact angleand tearing strength of the coated fabric were studied, the coating conditions were optimized bysingle factor experiment for these factors such as dosages of coating agent, baking temperatureand baking time, the properties of coated fabric were tested, and compared with that of the fabriccoated with pure waterborne polyurethane and waterborne polyurethane mixing with graphene.The results showed that with the dosage of IMG increasing, the surface resistivity of coatedfabric decreased, the water contact angle of coated fabric increased, and the tearing strength ofthe coated fabric increased. The conditions of coating process were that the coating agent dosagewas10g/m2, the baking temperature was160℃, the baking time was90s. As the content of IMGwas1%, the surface resistivity of the coated fabric was8.78×108Ω, the water contact angle ofthe coated fabric was116.88o, the tear strength of the coated fabric was115.6N, and thehydrostatic pressure of the coated fabric was4.8KPa. Compared with that of fabric coated withpure polyurethane, the antistatic performance of the coated fabric was improved significantly, and compared with that of fabric coated with polyurethane mixing with graphene, thehydrophobic performance, the tear strength and hydrostatic pressure of coated fabric wasimproved substantially, so as to get the coated fabric with antistatic and repellent properties.The dispersity of the graphene in waterborne polyurethane film can be improved after beingmodified with isocyanate. The electrical conductivity, water repellency, mechanical property andthe thermal stability of the IMG/waterborne polyurethane film can be all elevated. Meanwhile,the fabric coated with IMG/waterborne polyurethane has good water repellency and antistaticproperties. So that the waterborne polyurethane mixing with isocyanate functionalized grapheneis of high industrial application value on the functional finishing process of polyester fabric, andthe study has a certain guiding significance to expand the application field of graphene in textileindustry.