Research On Process And Properties Of Conductive Filled Polymer

Compared with metal and inherently conductive polymer, conductive filled polymercomposites have incomparable advantages, and it has been a hot issue in materials research inthe21th century. Researchers focus on the effects of forming process and multiphase filledpolymer composite on its conductivity and mechanical properties. The electrical conductiveproperties of polymer composites depend on not only the type, shape, mass fraction of thefillers and the features of the matrix, but also the forming conditions and microstructurecontrol during forming as well. Taken stainless steel fiber-filled polymer and hybridfiller-filled polymer as objectives, the conductivities were studied by the author to findoptimized processing conditions. In this paper, the effects of injection molding process,including injection pressure and packing pressure, on microstructure, mechanical properties,and conductivity were studied. The effects of multidimensional filler on the forming andintegrity of conducting network by multiphase filling were investigated and its mechanicalproperties were also analyzed.Firstly, the fibers distribution of stainless steel fibers filled polypropylene by injectionmolding was observed by Scanning Electron Microscope (SEM).The results show that theStainless Steel Fiber (SSF) removed into the sub-skin and core areas. The injecting pressurewas increased, accompanied by the shearing force increasing, to result in the removingvolume of SSF. While the volume of SSF in the sample of each layer increased withincreasing of packing pressure. Secondly, the mechanical properties of samples wereinvestigated by tension testing method, and the effects of injection process and filler quantityon mechanical properties were analyzed. The results show yield strength and plasticitydecreased with increasing of injection pressure, packing pressure and filler quantity. Finally,the electrical resistivity of overall and stripping samples were tested. The effects of injectionpressure and packing pressure on electrical resistivity and anisotropy were studied. The resultsshow the electrical resistivity of center area of sample is lower than that of margin area, whichis decided by the flow characteristics of melt. The electrical resistivity of skin layer increasedand those of sub-skin and core area decreased with the crease of injection pressure, and it hasdistinct anisotropy. While the electrical resistivity of each layer dropped with increasing ofpacking pressure. In addition, the Differential Scanning Calorimetry (DSC) curves show that high packing pressure is helpful for improving the degree of crystallinity of sub-skin and coreareas, which enhance the electrical resistivity.In the multidimensional filler filling PP test, the effects of multiphase medium onmicrostructure, mechanical and electrical resistivity of polymer composite were investigated.The experiments results show that Carbon Black (CB) and Nickel powder mainly distributedamong the fibers, and CB is help for orientation of fibers. Multiphase filler decreasedobviously the percolation threshold of conductive composites, which promote the forming ofconductive network. The quantity of SSF plays a key role on electrical resistivity ofCB-SSF/PP and Ni-SSF/PP polymer composites. CB decreased greatly the elongation at break,while Ni powders have a little effect.