Preparation of graphene plastics
The properties of graphene plastics (graphene modified plastics composites) can not be separated from the processing conditions in the preparation process.Different preparation methods lead to different dispersion, interfacial interaction and spatial structure of graphene in the matrix, which determine the stiffness, strength, toughness and ductility of the composites.
As far as we know, for graphene plastics, the degree of dispersion of graphene and the degree of stripping of graphene sheets can be controlled by controlling the shear force, temperature and polar solvent.
The physical preparation methods of graphene plastics include solution mixing method and melt blending method, and the chemical methods such as in situ polymerization method, emulsion mixing method, layer upon layer self-assembly technology (LbL), etc.
Solution mixing method
Solution mixing method is to dissolve graphene materials (GO, RGO) in a solvent to prepare a single layer of suspended graphene, which is dispersed in the polymer matrix to a certain extent.For example, modified GO was dispersed in an organic solvent and reduced to get graphene RGO, which was then mixed with the polymer solution to make composite materials.The graphene can be well dispersed in the polymer matrix by solution mixing.This method is widely used because of its good dispersion effect, fast preparation speed and the ability to control the state of each component.However, this method requires the use of organic solvents, which will cause adverse effects on the environment.
Melt blending is a solvent-free method in which the filler is dispersed in the polymer melt by the shear force generated by the extruder to overcome the interfacial force.The size and morphology of graphene are controllable due to the preparation of graphene and polymer respectively in the melt blend, but the graphene is concentrated in the polymer matrix and not easy to disperse, and the interface with the polymer is poor.Melt blending is a practical method for the preparation of graphene plastics. The process is relatively simple and can achieve large-scale and low-cost preparation. However, higher temperature and local pressure will affect the stability of each component of the composites.
In situ polymerization, graphene is mixed with polymer monomers and a catalyst is added to initiate a reaction. * composite materials are prepared.It was found that this method did not damage the thermal stability of the composite, but the reaction condition of in-situ polymerization was difficult to determine, and the addition of heat-conducting additives would have an uncertain impact on the polymer.
Emulsion mixing process
The emulsion mixing method takes advantage of the good dispersion of surface-modified graphene in water, mixes its dispersion solution with polymer emulsion, and then produces graphene/polymer composites through reduction.Compared with the melting blending method, the composite material prepared by emulsion mixing method has better dispersion effect and space stability, and this method does not use organic solvent and does not damage the environment.
Layer upon layer self-assembly technology (LbL)
Layer upon layer self-assembly (LbL) technology has advantages in the preparation of high strength ultrathin films, cell membranes and high strength coatings.This technology can * regulate graphene/polymer interfaces to make graphene well dispersed.
Industrial orientation of graphene plastics
The industrialization and research direction of graphene plastics are mainly in five aspects: conductive/anti-static functional plastics, thermal functional plastics, high-strength plastics, high-gas barrier plastics, and ion selection through the plastic film.
Conductive/antistatic functional plastics
Plastic itself is an insulating material with high surface resistivity, which limits its large-scale application in antistatic and conductive fields.Graphene has excellent electrical conductivity and a relatively large length and diameter. When it is filled into the plastic matrix, plastic with high conductivity and low percolation concentration can be obtained.
The low thermal conductivity of plastics limits their wide application in the field of thermal conductivity.The interface coupling between graphene-plastics and the thermal conductivity of graphene itself determine the thermal conductivity of graphene-modified plastics.
Graphene added to the plastic, can make the plastic thermal conductivity by 0.1 ~ 0.5 W/(m K) increased to 5 ~ 10 W/(m K), increased by more than 10 times, make plastic can be applied to the heat dissipation of LED lamp, auto radiator parts, electronic radiator shell and other fields, replace part of the common heat dissipation material such as aluminum, propulsion device of lightweight, expand the application areas of plastic.
High strength plastics
The mechanical strength of graphene is 100 times that of steel, which can greatly improve the mechanical properties of plastics.Common EPS foam has low mechanical strength, which limits some of its application fields.
When graphene was added to EPS as an additive, its mechanical strength was increased by more than 2 times. At present, graphene has been used in the field of foaming plastics, and also in packaging, military industry and other fields.Also, the high strength properties of graphene are utilized to develop new types of graphene vehicles. Graphene composite plastics are used as the skeleton and structural parts of vehicles, which can significantly reduce the weight of vehicles and save energy.
High gas barrier plastics
Graphene is a two-dimensional lamellar structure material with a very large specific surface area and excellent barrier property to gas molecules. When added to plastics, the network structure formed provides a curved channel for gas diffusion and extends the gas diffusion path, which can greatly improve the gas barrier property of plastics.In the field of plastic sealing, adding graphene can develop plastic sealing rings and seals that can withstand certain pressure.
Ion selection through the plastic film
After the surface modification of graphene, different groups can be added to make smart materials through the selection and arrangement of specific groups.Such as: can be through water but not through the oil film, oil and water separation can be achieved, applied to oil treatment and other fields.It can be used in industrial wastewater treatment, seawater desalination, salt chemical industry and other fields.