Study On The Mechanism Of The Sudden Drop In Mechanical Properties Of Graphene/polymer Nanocomposites

Graphene /polymer nanocomposites(GPNCs)are composites formed by graphene or graphene derivatives(dispersed phase)uniformly dispersed in a polymer(continuous phase).Over the past decade,GPNCs has received widespread attention.Studies have shown that graphene can significantly improve many of the properties of GPNCs,but it also tends to lead to the inflection point of "increase-decrease" in its mechanical properties,showing a "sudden drop in mechanical properties".This phenomenon has plagued the field of GPNCs for many years,but the lack of specialized research and accurate and reliable mechanism models directly hinders the development of the field.In view of this problem,this paper carried out a systematic study on the sudden drop in the mechanical properties of GPNCs,as follows:Firstly,due to the lack of research on the sudden drop in the mechanical properties of GPNCs,this paper firstly conducted a statistical study on relevant literature,summarized the relationship between the preparation method,mechanical properties type,graphene surface modification and other factors and the sudden change in the mechanical properties of GPNCs,and condensed out the basic rules.Then,the "cutting mechanism" is put forward to explain the above rules in theory.Laminated composites such as PVC/RGO/PVC were prepared and the "cutting mechanism" was verified by experiments.The finite element simulation further proves the "cutting mechanism".Based on the Most Probable Percolation Threshold(MPPT),two equations of Most Probable Critical Concentration(MPCC)were proposed to explain the sudden drop in the Concentration of mechanical properties.The MPCC equation shows that the sudden drop concentration is approximately inversely proportional to the aspect ratio of graphene.Based on the "cut-off mechanism",feasible strategies to further optimize the structure and performance of GPNCs are discussed.Finally,based on the deduction of "cutting mechanism",the sudden drop in mechanical properties of graphite fiber/polymer composites was further studied.The results show that the graphite fiber with quasi-one-dimensional shape also has the cutting effect,which can cause the mechanical properties of polymer composites to drop suddenly.The third MPCC equation is established and it is found that the sudden drop concentration is approximately inversely proportional to the square of the length-diameter ratio of the graphite fibers.In this paper,for the first time,a systematic study was conducted on the sudden drop of GPNCs mechanical properties,the basic law of the phenomenon was clarified,the "cutting off mechanism" was proposed and preliminarily confirmed through experiments,three MPCC equations were established,and feasible technical routes for further development in the field were discussed.The work of this paper has a direct promoting effect on the basic research and application research of graphene/polymer nanocomposites,and has certain reference effect on two-dimensional materials/polymer nanocomposites,carbon materials/polymer nanocomposites and other fields.