Preparation And Characterization Of Conductive Composites

Preparation and characterization of conductive composites.First,the polymer matrix and conductive filler are analyzed and selected,and the CB/MWCNTs/PP composite is determined.CB/MWCNTs/PP conductive composites were prepared by blending and injection molding of multi-walled carbon nanotubes(MWCNTs)masterbatch and carbon black(CB)masterbatch with polypropylene(PP).The morphological structure,thermal properties,piezoresistive effect and rheological properties of composites are investigated by changing the volume fraction of MWCNTs and CB.In this paper,the following research works are discussed,Firstly,calculating and weighing of MWCNTs masterbatch and CB masterbatch with PP,mixing by the high-speed mixer and marking the number,using the twin screw extruder to prepare the particles,drying and pouring into the injection molding machine to prepare different specifications of CB/MWCNTs/PP conductive composites.Secondly,the surface morphology,dynamic thermodynamics and crystallinity of the composites were investigated by changing the volume fraction of conductive fillers.The SEM diagram shows that with the increasing of the conductive filler,the particle gap becomes smaller and smaller,the conductivity of composites is enhanced.The doping of MWCNTs will improve the conductivity of composites.DMA results show that T_g and Phase transition temperature of the composites decreases with the increasing CB content,while the storage modulus and loss modulus increase with the increase of CB content in low temperature.POM results show that CB content have little effect on the spherulite size of PP,while the addition of MWCNTs decreased the spherulite size of PP gradually.Thirdly,The percolation threshold of composites decreases with the increase of MWCNTs conductive fillers.The slope of the initial stage of the stress-strain curve of the composite increases with the increase of strain rate and fillers content,appearing the strengthen of strain rate and the reinforcement of particle.When the conductive filler content lower or higher than the percolation threshold,the resistivity of the conductive composites showing the NPC effect,appearing hysteretic decrease with the increase of strain rate.when the conductive filler content around the percolation threshold,the resistivity of the conductive composites showing the PPC effect,appearing increase rapidly with the increase of strain rate.The elastic modulus of the composites increase with the increase of filler content,The tensile strength depends mainly on the compatibility of the matrix with the filler.Poisson’s ratio is not sensitive to CB content,has a negative correlation with the content of MWCNTs filler.Finally,the experimental of the rheological properties results show that CB/MWCNTs/PP composites are temperature sensitive material.whenφ<4%,γ<100%,the melting of composites appears linear viscoelastic behavior,γ>100%,the melting of composite appears nonlinear viscoelastic behavior.Viscosities of the composites are not sensitive to low frequency,in the low frequency,a little CB can be used as lubricant in the composite,the composite viscosity increases with the increase of CB content.when the volume fraction of fillers is between 2%~4%and composites reach the rheological percolation.With the increase of frequency,viscosities of the composites with different content of the filler are approaching to a consant,and exhibit shear-thinning.