Preparation Of High Performance Conductive Polystyrene Plastics

Carbon black filled bonductive plastics is a kind of ideal antistatic and electromagnetic shielding materials, which is widely used in plastic chip, portable power, display, robotics, life science and solar energy, and so on. In recent years, its industrial production has been realized. However, nanoscale conductive carbon black of carbon black filled bonductive plastics dispersed in the plastic matrix is not very well, it cause so many areas that require high performance conductive plastic need a lot of imports. At present, researches on carbon black filled conductive plastics are mainly concentrated in the modification of carbon black, extrusion technology studies mainly rely on the laboratory test equipment, those literatures based on pilot test equipment research to study the impact of twin-screw extrusion process on the properties of conductive plastic has not been reported. Moreover, there are few researches about the influence of the results of mechanical testing high-filled plastics or electrical performance testing in accordance with national standards or molding process on electrically conductive plastic mechanical and electrical performance test.In this paper, master batch was selected for research object firstly, using orthogonal design and uniform design method respectively and combination, to explore the optimization of high-filled plastic molding process. The impact of hot pressing temperature, pressing time and cold pressing temperature on the mechanical and electrical properties of conductive plastic was studied. On this basis, we focus on the influence of preparation process on the properties of conductive plastic. The premixed heating temperature, feeding sequence and premixed time in raw material pretreatment process, as well as the extrusion temperature, engine speed and times of extrusion passes in extrusion process were further studied. Finally, regression orthogonal experiment was designed to optimize extrusion temperature during conductive polystyrene preparation process.In this paper, we design an orthogonal experiment based on the moulding conditions commonly used; After took12uniform experiment in a wide range, we obtained ternary quadratic regression equations, and the optimal result prediction from it had deviation with the experimental result; Near the optimal results achieved from the uniform experiment, using orthogonal experiments and factors trend chart, the regression equation can be corrected, the predicted values coincide with the experimental values.Analysis showed that:when study on high-filled plastic molding process, orthogonal design was easy to analyze the results, but when studying on multi-factor experiment, the scope of factors and the number factors level was difficult to balance; Uniform design can quickly identify closer experiments point to the optimal solution, but to determine the regression equation, we usually required a combination of orthogonal analytical results; The combination of these two methods can be used in multi-factor within a wide range, selecting optimal solution process conditions more accurately and quickly, determining the primary and secondary of the factors, and establishing a credible mathematical models.Studied the pretreatment process, we found that, when the premixed heating temperature is higher than90℃, the material sticking phenomenon was eased; when heating temperature is120℃, master batch had the better conductivity.its volume resistivity was32.6Ω·mm. The result shows that, when the heating temperature is higher, caking sticking on the wall will be dispersed into the premix again. Studying on the feeding sequence and premixed time, we found that, the best feeding order was black\oil\sequential resin, premixed12min was better.Studying on extrusion process of conductive master batch, we found that, if the higher extrusion temperature increased in a properly range,the conductive master batch will have better conductivity. When extrusion temperature was240℃, the volume resistivity of the master batch was12.6Ω·mm. When the extrusion temperature is below180℃, the best engine speed is30Hz; When extrusion temperature was higher, the engine speed had less affected on the master batch resistance. Dispersing agent can effectively reduce the volume resistivity of the conductive master batch, powder dispersion Lrcoplus113and oily dispersant Solplus K220dispersed preferably, the master batch can be reduced to a volume resistivity of about10Ω·mm.Studying on the composite of conductive master batch and HIPS,we found that,the higher extrusion temperature was, not the better conductivity the conductive master batch had, nor conductive of the conductive polystyrene plastic prepared from it.After the second extrusion, conductive master batch was extruding granulation with HIPS, the composite effect is best, the volume resistivity of the conductive polystyrene plastic is16.8Ω·m. Optimizing extrusion temperature by orthogonal regression, the analysis showed that, the order of extrusion temperature affect on the conductivity of the conductive properties polystyrene plastic:composite extrusion temperature x3> master batch first extrusion temperature x1> master batch second extrusion temperature x2. The relationship between the three factors and the volume resistivity of the composite material meets the regression equation y=63.03+0.127xi-0.087x2-0.267x3.