Determination of plasticity of PVC hard products


The plasticity of PVC hard products is between 60% and […]

The plasticity of PVC hard products is between 60% and 70%. Too high or too low plasticity will affect the physical and mechanical properties and other properties of the products. To judge whether the processing technology is suitable and whether the plasticizing degree of the profile is ideal, the most fundamental method is to verify the physical and mechanical properties of the product and other properties. But from the results to verify, from a certain limitation, is not conducive to production. In the actual production, the following methods are used to judge whether the process is suitable, whether the plasticization degree is good, and the operator can be instructed to adjust the process in time.
(1) Observe the material status at the vacuum sight of the extruder
If the material is in the form of powder or completely loose bean dregs, the material is susceptible to vacuum suction, indicating that the temperature of the pre-feeding section and the plasticizing section is too low, and the material is not plasticized. If the material in the vacuum hole is plasticized very well. It is completely fused and glued together, and tightly coated on the screw, indicating that the plasticizing temperature is too high in the early stage, and the moisture and the hair in the material are not easily extracted from the dense melt. If the material in the vacuum is basically plasticized, it is roughly bonded into one body, slightly loose, with a certain luster and moderately coated on the surface of the screw, indicating that the material is plasticized properly, and the process of the previous stage is reasonable.
(2) Simple observation of the appearance of extruded embryos and products
The process is reasonable, plasticized suitable products, should be shiny on the surface, the inner ribs of the product are firmly bonded to the outer wall, the inner and outer surfaces are flat, and there are no bubbles inside and outside the slit and the product. The exit mold is soft and hard, shiny and smooth. Poor plasticization, the surface of the product is dull and dull, the product is brittle, and the inner rib is easy to break when the outer wall is stressed. From the extrusion die, the embryo is hard and dark, and the embryo is very hard and difficult to form; The surface of the ground product will be yellower than the normal product. When the port is cut, the port will be chipped and the product will be brittle. The embryo from the extruder is too soft to enter the shaping sleeve, and it is easy to drop the claws. By combining these actual phenomena with the process parameters, it can be judged whether the process is high or low.