Effect Of Bifunctional Graphene On Crystallization And Thermal Conductivity Of Nylon

Nylon 66(PA66),as a semi-crystalline engineering plastic with a wide range of uses,is one of the good resin matrixes as a thermally conductive polymer material.It is widely used in electronic and electrical,LED,heat exchange equipment,engineering components,aerospace and other fields,but With the continuous development of engineering technology,stricter requirements have been put on the thermal conductivity of nylon materials,as well as electrical conductivity,thermal stability,mechanical properties,etc.,so the development of modified thermally conductive nylon materials has been paid more and more attention.Commonly used modification methods to improve thermal conductivity include the addition of one or more thermally conductive fillers to increase their thermal conductivity and enhance electrical and mechanical properties.Graphene is a two-dimensional planar carbon atom nanomaterial.Its special molecular structure gives it ultra-high theoretical thermal conductivity,excellent mechanical properties,and extremely high electron mobility.It is used in thermally conductive materials,sensors,and new energy sources.Batteries,aerospace and other fields have attracted great attention from scientists and technicians,and have gradually become a new type of nano-thermal conductive filler.However,graphene is similar to other nanomaterials.The nanoscale effect of graphene will cause the problem of poor dispersion and easy agglomeration when added as a filler to the polymer matrix material.For the purpose of obtaining high thermal conductivity nylon 66 material,this topic modifies the graphene filler,which not only laps the graphene sheets together,improves the thermal conduction path,but also loads K+on its surface,destroying the function of PA66 crystallization through K+Improves the dispersibility of graphene fillers.The main research work is divided into the following two parts:(1)Preparation of modified graphene filler.First,the graphite is stripped into graphene oxide sheets as the thermal conductive filler of PA66.At the same time,the graphene oxide sheets are lapped together to improve the thermal conduction path and load K+on the surface that can destroy the crystal of PA66 to increase the graphene filler in PA66 The dispersiveness,so as to fully exert the heat conduction effect.The details are as follows:The Hummers method is used to peel the layered graphite into graphene oxide sheets,and the graphene oxide sheets are cross-linked with p-phenylenediamine to form a large sheet of graphene oxide fillers;Potassium is adsorbed on the surface of graphene oxide.The microstructure of the modified graphene was characterized by means of FTIR,Raman,SEM,TGA,XRD,etc.The results showed that p-phenylenediamine successfully cross-linked the graphene oxide sheet into a large overlapping layer structure,and expanded The graphene oxide sheet spacing,and potassium naphthalene acetate were successfully adsorbed on the surface and between the graphene oxide sheet layers,and finally the preparation process of the modified graphene filler was determined.(2)Preparation and performance of graphene filler modified thermally conductive nylon material.Several graphene/PA66 thermal conductive materials with different addition amounts were prepared by melt blending method.The crystallization curves of the above materials were measured by DSC.The results show that graphene oxide acts as a nucleating agent in the composite material.The effect of making PA66 is more prone to heterogeneous nucleation,and the crystallization rate of the composite material becomes slower,the crystallinity decreases,and after its adsorption of potassium naphthalene acetate,the supported K+can be combined with the carbonyl group in the PA66 amide Oxygen atoms undergo a complex reaction,which breaks the hydrogen bonds between PA66 molecules,further reducing the crystallinity of PA66,and achieving the purpose of regulating nylon crystallization.In addition,the thermal conductivity,electrical conductivity,mechanics,thermal stability and other properties of the composite material were measured through a series of test methods.The results show that when the filler contet is 20wt%,the thermal conductivity of the composite material is increased by 119%.compared to pure nylon.Conductivity has also been improved.It is proved that the modification of graphene to control the crystallization of nylon improves the dispersion of filler in PA66,so as to achieve the purpose of improving the performance of the material.