| Poly(propylene carbonate)(PPC)is a biodegradable and biocompatible polymer with excellent properties(such as toughness)obtained by polymerization of propylene oxide(PO)and carbon dioxide(CO2).However,its poor thermal stability and tensile strength constrain the practical application of PPC.Graphene oxide(GO)is efficient to enhance the thermal and mechanical properties of PPC,and GO is also supposed to improve the gas barrier property and the electrical property due to the great specific surface area and electronic transmission of GO nanopalte.Thus,the PPC composite modified by GO is prospective in the area of packing material,and the good dispersion of GO in polymer matrix is a key point.GO was prepared through the improved Hummers method and characterized by X-ray diffraction(XRD)and atomic force microscope(AFM).The structure and the defect of the GO nanoplate influenced the properties of the nanocomposites modified by GO to a great extent,in this work,three kinds of graphene derivatives: GO(made by Hummers method),RGO-VC(reduced by vitamin C),GNP(graphene nanoplate made by mechanical exfoliation method)were used to improve propertiy of the PPC composites.Here,the composites were made by the solution exchange method and the barrier and electrical properties were studied mainly.The results show that the barrier property of the PPC composites by adding 1.0% nanofiller improved at least 10 times compared with that of pure PPC,and the PPC/GO composite was the best.As to the electrical properites,the electrical resistivity of the PPC/GO composite decreased by 4-5 orders of magnitude,better than that of PPC/RGO-VC and PPC/GNP composties obviously.This was attributed to the better dispersion state of the GO nanosheets in the PPC matrix.For further study,the influence of GO contents to the barrier and electrical properties of PPC/GO composites was analysised.And it was found that the barrier property of PPC/GO composites improved more than 10 times even with 0.1% GO,the oxygen permeability decresased by 88.44% than that of pure PPC,and the electrical resistivity decreased by 2 orders of magnitude at the same time.When the GO content increased to 0.5%,the oxygen permeability decreased a little than that of PPC/0.1GO nanocomposites,and the electrical resistivity continued to decrease 3 orders of magnitude.It could be speculated that the network structure created by the GO nanosheets appears.Melt blending was still one of the best methods to realize the application of polymer materials so far,thus solution blending and melt blending were combined to make GO well-dispersed in the Poly(propylene carbonate)(PPC)matrix.The poly(vinyl alcohol)(PVA)and poly(ethylene glycol)(PEG)acted as a dispersion medium.The obtained PPC/PVA/GO nanocomposites displayed an improvement in mechanical properties by adding 10% PVA and a small amount of GO.The results showed that,the thermal stability and mechanical strength was improved to some extent with the increase of GO content,and the comprehensive performance of the PPC/PEG/GO composite was optimal at the GO content of 0.5phr.The tensile strength and the young’s modulus of the PPC/PEG/0.5GO composite was 4.1MPa and 52.31 MPa,higher than that of the pure PPC respectively.The elongation at break was kept at a relatively high level.Furthermore,the glass transition and the decomposition temperature improved about 1.5℃ and 50℃ at the same time.As for rheological properties,the complex viscosity as well as the storage modulus and loss modulus of PPC/PEG/0.5GO composite was also the highest at the low frequency range during testing.However,if the GO content continued to increase,these properties of the composites would deteriorate on the contrary.It might be attributed to the GO aggregation,which could be proved by the SEM and TEM images. |
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