| As a sort of functional materials, conductive polymer composites have been extensivelyused in many fields of electronic, energy and chemical engineering and was considered as oneof the most prospect materials. Injection molding is a important method in the contourmachining process of conductive polymer composites. The special skin-core structure whichformed during the injection molding have an significant effect on the structure and propertiesof composites. So the relationship between injection processing and micro-structure wasensured is helpful to choose proper parameters to improve the conductivity of composites.A series of conductive composites under different injection processing and quality scorewith Carbon Black (CB) and Stainless Steel Fiber (SSF) as filling, polypropylene(PP) as thematrice was prepared. The effection of quality score and injection processing tomicro-structure was studied. The influence of injection processing on electricity, mechanics,thermology was discussed. Conductive model of composites were studied based onexperiments.1、Results were obtained from the studied of CB/PP：(1) The rheology analysis of PP and CB/PP composite was studied. The apparentviscosity of PP reduced with the increase of the shear rate, the apparent viscosity of CB/PPimproved with the increase of the shear rate. The linear relationship between shear rate andapparent viscosity was demonstrated in a narrow range.(2) The orientation was formed at the skin and core zone after orientation analysis ofinjection CB/PP. The orientation was not occurred at skin zone, but occurred at core areabecause of the rapid cooling in the experiment.(3) The migration of CB decreased from skin to sub-skin zones with the increase ofinjection pressure under the same packing injection. The resistivity of skin, sub-skin and corezones decreased with the increase of packing pressure under the same injection pressure,Improve packing pressure is beneficial to the formation of the composite conductive network.CB was distributed in the form of aggregates similar to grapes in the composites.(4) For injection spline, the resistivity raised because of the migration of CB with theinjection pressure increased, the absorption of electromagnetic wave declined. The amount of CB in the spline increased along with the increase of the pressure. The resistivity of the splinedecreased and the absorption of electromagnetic wave enhanced. The best conductivity of thecomposite material was obtained with the injection is70MPa and packing pressure is50MPa.(5) The crystallinity of composites increased with the addition of CB compared PPbecause of CB particles act as the nucleation agent during the crystallization. Increase ofinjection pressure and packing pressure make macro-molecular orientation, crystallinityincreased because more crystallization nuclear was induced.2、Results were obtained from the studied of SSF/PP：(1) The migration of SSF from skin zone to sub-skin and core zone under the action ofshear stress, as a result, the resistivity of skin is greater than sub-skin and core zones with theamount of SSF changed in the three zones. The number of fiber in the sample increased withthe packing pressure enhanced, and the resistivity of samples droped. The electromagneticwave absorption of the samples reduced with the increase of the resistivity.(2) With the quality score increased of SSF, The resistivity, tensile strength and breakrate of sample droped. The tensile strength and break rate of sample droped with the injectionpressure and packing pressure increased.Base on the distribution state of CB and SSF in matrix and the conductivity of thecomposites which was influenced by the state. Conductive model was built to forcast theresistivity of the sample, the electromagnetic shielding effectiveness was evaluated accordingto the results. In this paper, the mathods of GEM and data fitting was used to built theconductive model, the result of model prediction is well after tested. |
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