Zhendelong Machinery (Kunshan) Co., Ltd.

Extruder

Sheet Extruder
EPDM is a terpolymer of ethylene, propylene and non-conjugated diene. [ ] Diolefins have a special structure. Only EPDM rubber with one of the two bonds can be copolymerized. The unsaturated double bond is mainly used as a cross-linking site. The other unsaturated one will not become the main chain of the polymer, but will only become the side chain. The main polymer chains of EPDM are fully saturated. This property makes EPDM resistant to heat, light, oxygen, and especially ozone. EPDM is non-polar in nature, resistant to polar solutions and chemicals, has low water absorption and has good insulating properties.
In the production process of EPDM, its characteristics can be adjusted by changing the amount of three monomers, the ethylene-propylene ratio, the molecular weight and its distribution, and the vulcanization method.
The first stage is the plasticization stage. Also called the compression phase. It is completed in the barrel of the extruder. Through the rotation of the screw, the plastic changes from a granular solid to a plastic viscous fluid. There are two sources of heat for plastics in the plasticizing stage: one is the electric heating outside the barrel, and the other is the friction heat generated when the screw rotates. The initial heat is generated by the electric heating outside the barrel. After normal operation, the heat is obtained by the friction between the screw and the inner wall of the barrel during the compression, shearing and stirring process of the selected material and the internal interaction between the material molecules. Produced by friction. The second stage is the shaping stage. It is carried out in the machine head. Due to the screw rotation and pressure, the viscous fluid is pushed to the machine head. Through the mold in the machine head, the viscous fluid is formed into required extruded materials of various sizes and shapes, and then packaged. Covered outside the core or conductor. The third stage is the finalization stage. It is carried out in a cooling water tank or cooling pipe. After the plastic extrusion cladding is cooled, it changes from an amorphous plastic state to a shaped solid state. 3. Changes in plastic flow during the plasticization stage
During the extrusion process, depending on the way of pressurizing the plastic, the extrusion process can be divided into continuous and intermittent. The equipment used in the former is a screw extruder, and the latter is a plunger extruder. Screw extruders are divided into single-screw extruders and multi-screw extruders, but single-screw extruders are more commonly used. When extruding with a screw extruder, the plastic loaded into the hopper enters the feeding barrel through the rotating screw (wet extrusion does not require heating). Due to the external heating of the barrel and the shear between the plastic itself and the plastic and the equipment, Frictional heat causes the plastic to melt and become fluid. At this time, the plastic is evenly dispersed by the stirring of the screw and continues to advance. Finally, the plastic is extruded out of the machine by the screw at the die to form a continuum, which is cooled and solidified to become the product.
The main components of a plunger extruder are a barrel and a hydraulically operated plunger. During operation, first place a batch of plasticized plastic in the barrel, and then use the pressure of the plunger to squeeze the plastic out of the die. After the plastic in the barrel is squeezed out, the plunger should be withdrawn for the next operation. . The biggest advantage of the plunger extruder is that it can give greater pressure to the plastic, but its obvious disadvantage is that the operation is discontinuous, and the material must be pre-plasticized, so it is rarely used. It can only be used during extrusion. Polytetrafluoroethylene plastics and other surface applications are still available.
As mentioned above, the vast majority of plastics extruded are thermoplastics. In addition, in terms of equipment, single-screw extruders are widely used, and twin-screw extruders are increasingly important in PVC processing and batching.