2022-05-25
Conductive PP compound is formulated with PP resin and conductive carbon black .It's widly used in a different field by processing method,Different addition level and the dispersion quality are key factors forachieving good conductivity.Let's introduce each processing method.
Predrying
As the carbon black contained in the compounds ,conductive PP compound is hygroscopic, they should be stored in a dry place, Conductive PP compounds need to be predried before processing. Processing an undried conductive compound with a high moisture content can result in deficiencies in the final product, such as surface blemishes in molded parts, holes in extrusion sheet, and other unwanted results.
Processing
Conductive PP compounds can usually be processed on conventional processing equipment. To promote good electrical and mechanical properties of the material, it is advisable to process the compounds under low shear conditions. In fact, conductive carbon black filled compounds are highly shear sensitive. Too much shear can deteriorate carbon black networks and reduce conductivity.Processing equipment and parameters should be carefully selected so that the shear generated is kept to a minimum.
Injection
There are no special requirements for the selection of injection molding machines. Because conductive PP compound has high crystallinity. A computerized injection molding machine with higher injection pressure and multi-stage control is required. The clamping force is generally determined as 3800t/m2, and the injection volume is 20%-85%.
The melting point of PP is 160-175°C, and the decomposition temperature is 350°C, but the temperature setting cannot exceed 275°C during injection processing. The melting section temperature is preferably 240°C.
In order to reduce internal stress and deformation, high-speed injection should be selected, but some grades of conductive PP and molds are not suitable (bubbles and gas lines appear in the mantle). If the patterned surface appears with alternating light and dark stripes spread from the gate, low injection speed and higher mold temperature should be used.
Conductive PP compounds can be injection molded to produce equipment housings, fan blades, pallets, caps, and other products .
Extrusion
The conductive compounds are put into the internal mixer. they are mixed by the rotor of the internal mixer, pressurized and pressed, and conductive compounds are formed in the internal mixer. The materials are kneaded into pellets through the action of the rotor and the crusher and then turned into the elevator and sent to the cone double feeder through the elevator. The materials are evenly fed to the single unit through the cone double feeder. In the screw, the material is stably extruded through a single screw. During the extrusion process, the plastic enters the barrel with the help of the feeding screw. Under the thrust of the rotating screw, it continues to push forward, starting from the preheating section and gradually moving to the homogenizing section; push into the machine head; the material flow reaching the machine head passes through the annular gap between the mold core and the mold sleeve, and the sheet is extruded from the mold sleeve mouth. The sheet enters the three rollers for shaping, cooling and leveling, and is cooled by the cooling guide roller bracket. The product size timer determines the size and cutting, the cut products are packaged, and the entire conductive PP sheet extruding process is completed.
The conductive PP sheet extruder needs to pay attention to the working temperature of the three rollers. Generally speaking, the temperature of the incoming roller should be slightly higher and the temperature of the outgoing roller should be lower.
The molding mold temperature is slightly higher than the barrel temperature, and the higher temperature needs to be between 5 and 10 degrees.
The temperature control of the molding die of the conductive PP sheet extruder needs to be stable. Instability will cause large longitudinal errors in the sheet products.
Conductive compounds are widely used in the electronics industry. Such like Polystyrene carrier tapes,Polystyrene thermoformed trays,Polypropylene corrugated sheet.
