Research On Conductive Plastics And Molding Process For Automobile Fuel System

With the rapid development of national economy, the development of automobileindustry has become one of significant signs of the modern civilization, science andtechnology for a country. With the progress of technology, the growth of automobile and therelevant industries make contributions to society. On the other hand, it leads to side effects toenergy supply and environment protection of society. Under the driving of energyconservation and emissions reduction trend, automobile wight reduction has become animportant developing trend of automobile industry. The application of light weight materialscan not only reduce the weight of cars effectively, but guarantee the safety and economy.Preparation of the conductive polymer composites meeting the require of Society ofAutomotive Engineers （SAE） standard fuel system and influence of its injection moldingprocess on properties of products were investigated in this study, using the material system ofcarbon fiber reinforced polycarbonate for automotive fuel oil system. The carbon fiberreinforced polycarbonate composites was prepared by melt blending in this paper. Theinfluence of different surface modification methods for carbon fiber on the compositesmicrostructure was studied to improve the interface bonding force between carbon fiber andpolymer matrix. Furthermore, the mechanical and molding process properties of the materialinjection mold samples were also tested. In order to analyze the material adaptability to thefuel filter of injection molding process further, The performance of the injection moldingprocess of the fuel filter was simulated by moldflow analysis. The research results are asfollows:1. Compared with those of the untreated samples, the tensile strength of the sample hasthe maximum value as carbon fiber is oxidized at500℃for1h, which is increased by13.3%,and the tensile modulus increases by8.9%.2. In carbon fiber with the nitric acid treatment, the longer treatment time is, the deeperetch in the carbon fiber surface have and the stronger the binding force with the matrix resin is.But the surface of fiber get seriously damaged and mechanical properties of compositematerials decreased when the processing time is too long. It was found that tensile strength ofcomposites was improved in nitric acid treatment for5h, and tensile strength and tensilemodulus were increased by23%and16.9%, reached90.8MPa and6945MPa, respectively.3. In the condition of coupling agent treatment after pre-oxidation treatment for carbonfiber surface the tensile strength of the samples increases significantly. The tensile strength ofthe sample improved by30.2%, reached97.7MPa after the treatment of aqueous solution of coupling agent with the concentration of1%.4. By sizing treatment on carbon fiber surface using carbon nanotube composite carbonfiber sizing agent, mechanical properties of CF/PC composites are greatly improved, and it’stensile strength reached108.2MPa, increased by44.2%, and tensile modulus reaches7830MPa, increased by30.2%. Meanwhile, the resistivity of the composite material issignificantly reduced to3.07×104Ω·cm, because of the overlapping of carbon nanotubes,which can meet demand of antistatic material.5. Fiber orientation phenomena occurred within the samples due to the shear stressduring the injection molding. Meanwhile, carbon fiber migrated to the subskin and core zoneunder fluid shear stress because the skin melt cools faster than those of subskin and core. At afixed holding pressure, the tensile strength of the sample increases with increasing theinjection pressure, and it drops after reaching a extreme value. And, the skin resistivity of thecomposite material increases due to the shear stress improving. At the same injection pressure,the tensile strength of the sample increases as the holding pressure increases, and theresistivity decreases firstly and then increases. The reason why the resistivity decreases is thatthe fiber increases when holding pressure promotes, and resistivity increasing is that fiberorientation becomes significant due to shear stress enhancing, which is adverse to forming theconductive network when holding pressure continue to rise. At the same injection pressureand holding pressure, the increasing of mold temperature has a little influence on tensilestrength, but lowered the resistivity distinctly.6. It is showed that simulation results agree with experimental observation results byanalyzing the filter CAE molding and simulating the fiber orientation.