Views: 113 Author: Site Editor Publish Time: 2020-11-26 Origin: Site
In the production process of plastics compounding, it is relatively troublesome to encounter powdered raw materials. The powder is easily inhaled to the lungs, causing harm to the body, and there is a danger of dust explosion. Processing SEBS into TPE will also turn the powder into granules or make some modifications.
It is more convenient to feed granular material than powder material, without a compulsory feeder.
The density of pellets is higher than that of powder, and the product quality is good.
The volatile matter and air content are less, and the product is not easy to produce bubbles.
Using functional masterbatch is easier to disperse than directly adding functional additives.
The temperature has a significant effect on the performance of TPE extrusion and parison: it can reduce the melt viscosity, improve the fluidity of the melt, reduce the power consumption of the extruder, and appropriately increase the screw speed without affecting the mixing of materials.
The chemical effect is conducive to improving the strength and brightness of the final product and the transparency of the final product. However, if the melt temperature is too high, the extruded parison will easily sag under its weight, causing uneven longitudinal wall thickness of the parison.
Therefore, the principle should be followed to set the heating temperature of the twin screw extruder. On the premise that a smooth and uniform parison can be extruded without overloading the transmission system, to ensure a higher melt strength of the parison, a lower heating temperature should be used as much as possible.
The pressure of the melt entering the die head should be even. Properly increase the pressure of the melt in the extruder to make the materials evenly mixed and stabilize the performance of the parison and the final product. To control the melt extrusion pressure, a melt pressure gauge can be installed in the discharge port of the extruder.
The higher the melt conveying speed, the larger the extrusion capacity of the extruder. Increasing the conveying speed of the melt can improve the sag of the parison and increase the wall thickness of the parison.
In addition to the extrusion process, the pelletizing process also has a greater impact on the product. At present, it is mainly divided into two types: cold cutting and die face hot cutting.
The materials passed through the kneader or internal mixer are molded into sheets by an open mill and then cut into pellets after cooling.
The kneaded material is plasticized by an extruder and then extruded into a sheet, then air-cooled or naturally cooled, and then cut by a flat pelletizer.
Extrusion cold cutting is the most common granulation method for thermoplastic TPE, and the equipment and process are relatively simple. The material is plasticized by the extruder into round bars and extruded. After the round bars are air-cooled or water-cooled, they are cut into cylindrical pellets by a pelletizer.
Place the rotating cutter tightly on the die plate, and directly cut the extruded hot round strip into pellets.
It is a new technology of polyolefin TPE granulation. The die head and cutter work in circulating warm water.
It is similar to dry and hot cutting. To prevent particles from being adhered to, the pellets are cooled by blowing cold air or spraying warm water in the pelletizing hood.