| Graphene has excellent mechanical properties, electrical properties and large specific surface area and remarkable adsorption properties and other characteristics, and has a wide range of applications in polymer nanocomposites. In this paper, graphene oxide (GO) and it can exist stably at room temperature,(TRG) was used as the reaction starting materials for different graphene-based polymer nanocomposites prepared by a chemical and physical approach, and the outstanding performance of the composite materials in mechanics, thermodynamics, crystallization behavior, gas-barrier, and surface hydrophobicity were studied and evaluated. Our main works are as follows:(1) Thermal reduced graphene was prepared in a quick and easy way. By Controlling the reduction temperature and time,16groups of graphene samples with different degree of reduction was obtained. We applied the infrared spectroscopy, Raman spectroscopy, X-ray diffraction, thermal gravimetric analysis, surface photoelectron spectroscopy, surface resistivity test to study the relationship between structure and properties of graphene. By means of high-resolution transmission electron microscopy, scanning electron microscopy and atomic force microscope, we can clearly distinguished the graphene surface wrinkles and defects restored. Raman spectroscopy showed the ratio of the thermal reduction degree as ID/IG to restore graphene is1.82, compared to chemical reduced graphene (CRG) of2.23. It can be seen the degree of reduction of the carbon lattice was significantly enhanced. Reaction at1050°C,40min bear the lower resistivity of0.073Ω·cm compared to0.00515Ω·cm of natural flake graphite, It prove that the process of rapidly heating upon graphene increased the degree of graphitization, and enhanced their thermal stability. Aspect ratio of graphene, observed by transmission electron microscopy and scanning electron microscopy in the nanometer size range, increased several times. Graphene’s surface with more folds is more likely to react with a polymer-based body in a liquid phase to maintain a stable chemical state, which has a special functional application in the graphene-based polymer matrix composite films.(2) In situ polymerization of graphene reinforced nylon6composites. Graphene oxide as a raw material was involved in the polymerization reaction for different weight percentages of graphene/nylon6composites. Mechanical properties of the testing results showed that the graphene relied on its own high specific strength and specific modulus as well as physical crosslinking points in the polymer matrix to form an effective graft chain molecules in the surface. The crosslinking render external load transfer quickly to enhance the strength and modulus of the composites. Polymer chain graft rate in graphene surface with different content of the graphene/nylon6composite can be roughly determined by thermal gravimetric analysis. Plane diffraction of nylon6showed a typical double-peak, and the lower lattice plane index could move to the higher plane index with increase of the amount of graphene in the nylon crystalline region.(3) The method of liquid-phase compounding was used in the preparation of graphene (TRG)/poly (ethyl vinyl alcohol)(EVOH) composites with different TRG weight fraction. TRG after high temperature rapid thermal reduction can be well dispersed in an organic solvent, and hydrogen bonding were formed between the oxygen-containing groups of TRG and hydroxyl groups of the EVOH polymer chains, then help TRG reached the molecular level dispersion in the polymer matrix. Mechanical testing showed that4.0wt%of graphene in EVOH matrix has increased by280%in tensile strength and400%in modulus with respect to the pure polymers. Such composite films bear a lower surface free energy (-40.5mJ/m) and a better surface hydrophobicity (CA119°), a high glass transition temperature and thermal decomposition temperature, as well as excellent gas barrier properties (such as0.5wt%content of TRG in EVOH functional films can improve the barrier properties of the oxygen molecule nearly2400times), so this films is hopeful to get widely used in food preservation and clinical drug packaging.(4) The preparation and application of thermal reduced graphene/poly (vinyl alcohol) composite materials. Using liquid-phase mixing technique, the composites with different content of TRG was prepared. We know that the poly (ethyl vinyl alcohol) is similar to the chemical structure of the poly(vinyl alcohol), In which the end of the molecular chain has a richer hydroxy, and is therefore very easy to absorb moisture and reduce its mechanical properties and thermal stability. However, the gas barrier properties and surface hydrophobicity of the pure poly(vinyl alcohol) as a function of film material is not satisfied. The two-dimensional graphene with monatomic layer thickness has a great specific surface area, mechanical modulus, and thermal stability, and can form the tortuous path to block the gas molecules passsing though the polymer matrix.the experimental results demonstrated that TRG was homogeniously dispersed in a polymer matrix to form both the excellent gas-barrier property, highly water drops permeability, remakable thermal stability and good thermo-mechanical properties of composite materials. Gas permeability tester, optical contact angle meter and a series of characterization tests confirmed the graphene/PVA nanocomposites could be used as a functional barrier packaging material to extend the shelf life of food. |
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