The Study On Mechanical Properties Of Polyethylene/Graphene Composites Reinforced By Epiphytic Crystallization

Polymer nanocomposites are composite materials prepared from polymer materials by adding nano-materials,which is an effective way to prepare high-performance polymers.In the preparation of polymer nanocomposites,the interfacial interaction between polymer matrix and nanofiller can affect dispersion of nanofiller and even the ultimate property of composite materials.In this paper,we select two kinds of polymer matrix with similar molecular chain structure by adding inorganic nanomaterials to study the effect of space restriction and epitaxial crystallization on mechanical properties of polymer matrix.First,the influence of space confinement between two-dimensional(2D)layered reduced graphene oxide(RGO)and isotactic polypropylene(iPP)on the crystallization and mechanical properties was investigated,with no epitaxial crystallization.On this basis,RGO was use to investigate the influence of space confinement and epitaxial crystallization on the crystallization and mechanical properties of high density polyethylene(HDPE).In order to better understand the effect of RGO on different parts of the injection bar under the mechanical properties of RGO/HDPE nanocomposites was enhanced,the change of microstructure from edge to center was investigated.Based on above,the structure evolution of HDPE/RGO nanocomposites under different strain was observed by using in-situ X-ray technology,and then the enhancement of mechanical properties of HDPE/RGO nanocomposites were analyzed.Differential scanning calorimetry(DSC),wide angle X-ray diffraction(WAXD),small angle X-ray scattering(SAXS)and mechanical performance test were used to investigate the interfacial interactions and their effects on the final properties of polymer nanocomposites.The main results are as following:1.IPP/RGO bars were prepared by injection molding technology,and the effect of space restriction between polymer and nanomfillers on the crystallization and mechanical properties of composites was studied.It was found that the effect of RGO on the crystallization behavior of iPP matrix had double effects: firstly,RGO could be used as a nucleating agent to promote the nucleation of iPP.At the same time,the two-dimensional layered structure of RGO also inhibits the relaxation of the iPP molecular chain in the process of injection,the mechanical properties of iPP matrix could also be improved as nanometer reinforcing material..2.HDPE was selected as a model polymer to investigate the influence of epitaxial crystallization on the mechanical properties of HDPE/RGO nanocomposite injection bar.The study found that the mechanical properties of nanocomposites were improved by the double effect of space restriction and epitaxial crystallization.Compared with the iPP/RGO nanocomposite injection bar with no epitaxial crystallization,the enhancement of the mechanical properties of the nanocomposites injection bar was more significant.3.To study the effect of RGO on local microstructures of HDPE/RGO nanocomposite bars.The equidistant point of the bar from the edge to the center is studied by using the microbeam 2D SAXS technique.It is found that RGO affects the entire bar.4.The influence of RGO on the structure and properties of HDPE matrix was further studied.The results showed that the addition of RGO caused the deformation of HDPE structure to be delayed in the stretching process.