The Preparation Of MgO Nanoparticles-grafted Carbon Fibers/Nylon 6 Composites And The Research Of Its Thermal Conductive And Insulating Properties

With the rapidly development of electronics technology industry,various electronic device continuously toward miniaturization,energy conservation,intelligence direction puts forward the higher requirements for heat dispersing and insulation of materials.The traditional thermal insulation materials are mostly composited by inorganic nanoparticles and polymer,However,this kind of methods need high packing and cost,its mechanical properties will also be obviously decreased.However,if we fill carbon materials,metal materials as thermal conductive filler into the polymer,the thermal conductive and mechanical strength of materials will be improved,on the contrary,the insulation is decreased apparently.So the materials with good thermal conductive,insulation and mechanical strength under the low filler is an important development direction of thermal conductive materials.In order to prepared with good thermal conductivity and insulating properties of materials,we pitched magnesium oxide particles on the surface of carbon fiber to get a new type of thermal conductive insulating filler by chemical bond,and then fill it into filler Nylon 6 matrix.In this paper,we used the method of cross coupling agent treatment to modify carbon fiber(CF)and MgO nanoparticles,and then the MgO nanoparticles were successfully pitched on the surface of carbon fibers(CF-MgO)by the reaction between amino and epoxy on different surface and filled these thermal conductive and electronic insulating composite filler in Nylon 6 in the end.After the treatment by different coupling agents,the interfacial strength of fillers and resin were improved obviously and the interface thermal resistance reduced obviously;Using the excellent thermal conductive and mechanical strength of carbon fiber to improve the heat dissipation and strength of composite;Using the good insulation and thermal conductivity of MgO nanoparticles to form the thermally conductive and insulating area between fillers and resin.Firstly,we found the optimal process parameters by control the length of carbon fiber,the type and concentration of coupling agent and the rotation speed of screw.The experimental results show that the thermal conductivity of CF/PA 6 composites was the best at 2-3 mm of carbon fiber initial length,100 r/min of screw speed,3wt%concentration of coupling agent KH550,and the percolation phenomena of thermal conductive is appeared by 7-10wt%packing.On the condition that the processing parameters above were invariant,the surface of carbon fiber was introduced hydroxyl,carboxyl and amino group after its modified by desizing,acidification,coupling agent treatment.MgO particles were treatment by KH560 coupling agent to make the epoxy groups pitch on fibers(MgO-KH560),and then we mixed CF-KH550 and MgO-KH560 together to get the new fillers(CF-MgO).The grafting rate of carbon fiber surface was controled by MgO particles content,the concentration of coupling agent,reaction time and temperature.The experimental results show that:the grafting rate of MgO particles on the surface of carbon fiber was best at the density of 4wt%(MgO-KH560 particles)and reaction at 100? for 8 h,its grafting rate reached nearly 9%.Studied the packing of CF-MgO impact on thermal conductive,insulation and mechanical properties of CF-MgO/PA6 composites.The experimental results show that compared with the pure carbon fiber,the thermal conductivity of CF-MgO/PA6 composites reached 0.748(W/m K)when 20wt%packing.Not only these,but the surface resistivity of composite was very high when the packing was 10wt%,remained insulating materials.