The Preparation And Characterization Of Polyolefin/Graphene Oxide Composites

Polyolefin(including polypropylene,polyethylene)has been widely used in package,buildings,automotive field due to the excellent properties,such as chemical stability,easy processing and low cost.However,compared with other engineering plastics,the drawbacks of polyolefin(low strength,poor thermal stability,poor thermal conductivity,low electrical conductivity)seriously limit its advanced applications.The modification to polyolefin resins is believed to be meaningful to extend the application fields.Which could not only improve the intrinsic properties,but also endue more functionality,eventually greatly increase the added value of polyolefin materials.Polymer-based composites were heralded in the 1960s as a new paradigm for materials.By dispersing strong,highly stiff fibres in a polymer matrix,high-performance lightweight composites could be developed and tailored to individual applications.Graphene,the firstly reported one-atom-thick two-dimensional layers of sp~2-bonded carbon,is preferred as the perfect filler to enhance the polymer matrix due to the excellent physical properties.However,the compatibility and interfacial interaction between graphene-polyolefin matrix and the challenges that remain to achieve good dispersion pose significant obstacles to harness the excellent properties of graphene in polyolefin.Herein,the graphene oxide(GO),which can be easily prepared from natural graphite,is prefered to enhance the polyolefin due to the high strength and modifyability.The alkylated methods and exfoliation mechanisms of GO are systematically and deeply studied,the alkyl GO(MGO)is incorporated in polyolefin by solution compounding,two-step blending and melt blending to study the performance evolution of polyolefin based MGO composites.In addition,the performence influence factors of polyolefin based RGO composites are systematically designed and studied to lay the theoretical and experimental foundation to the preparation of high-performance polyolefin based graphene nanco-composites.The detailed contents are as following:1.The graphene is prepared form three different synthesis methods(Electrochemical exfoliation,Supercritical fiuld expansion,Chemical oxidation)to study the availability in polyolefin based graphene composites.GO is preferred to enhance the polyolefin matrix due to the high quality,scalability and reactivity.2.The GO is alkylated by covalent grafting and non-covalent grafting method to evaluate the availability in scalable production of polyolefin/MGO composites.Among them,alkyl ammonium oxide(AAO)can rapidly alkylate GO in the aqueous phase by virtue of its high reactivity,and the modified MGO exhibits excellent lipophilicity.After incorporated in polyolefin matrix by solution compounding,MGO can significantly increase the thermal,electrical,and mechanical properties of the polyolefin matrix.3.The two-step compatibilizaiton method(solution compounding+melt blending)is designed to improve the dispersibility of MGO in polyolefin prepared by melt blending,the enhancing mechanism is further investigated.4.The alkyl reduced graphene oxide(M-RGO)is one-step synthesized by a green and facile low temperature expansion method to enhance the polyolefin by twin-screw melt blending.The exfoliation mechanism of the GO and enhancing mechanism of polyolefin/M-RGO are further studied.The method is green and convenient.The preparation condition requires neither a high temperature conditions nor the low vacuum equipment.Based on the full exfoliation to alkyl graphite oxide,the low temperature condition effectively avoids the decomposition of alkyl modifier,and retains large alkyl modifier.The effective alkyl modification and high exfoliation degree of M-LTRGO provide the kinetic and thermodynamic conditions for preparation of high-performance polyolefin composites by melt blending.5.The surface alkyl degree,exfoliation degree and size distribution-controllable RGO is one-step synthesized by adjusting the process parameters of low-temperature expansion.It is further incorporated in polyolefin by twin-screw melt blending to study the enhancing mechanism of the polyolefin/RGO composites.Based on the alkyl modification,the higher specific surface area result the better mechanical properties.The relationship between alkyl degree and exfoliation degree of M-RGO during the low temperature expansion process is investigated.6.The carbon fiber(CF)is modified with GO by ultrasound-assisted self-assembly,then the GO@CF is alkylated to enhance the LLDPE by mixer melt blending.As the interface material,GO could significantly enhance the mechanical properties of the LLDPE/MGO@CF composites,the enhancing mechanism is discussed and studied.Finally,the low-voltage heating performance of the flexible film is also investigated.