PVC extrusion is a molding process used to manufacture PVC products (such as pipes, profiles, plates, etc.). This article will detail the processes involved and what to pay attention to in each operation process.
PVC resin and auxiliary materials need to be prepared in advance before PVC extrusion. PVC resin is the main raw material of PVC products, and auxiliary materials include plasticizers, stabilizers, flame retardants, pigments, etc. These auxiliary materials need to be scientifically matched according to the characteristics of the finished product to ensure the final quality.
The mixing and pretreatment of PVC resin and auxiliary materials are key steps in the PVC extrusion process. Usually, a mixer is used to fully mix the raw materials to ensure that various additives are evenly dispersed in the PVC resin.
During the mixing process, it is necessary to reasonably configure the proportion of each component, especially the amount of stabilizer and plasticizer added. The ratio of these auxiliary materials will eventually affect the performance of the finished product.
During the mixing process, it is necessary to ensure the uniformity of various materials to avoid inconsistent product performance or obvious color differences.
In addition, during the mixing process, temperature control is very important to avoid excessive temperature-causing material decomposition or performance degradation.
The mixed PVC material is transported to the screw of the extruder through the feed port. Under the rotation and heating of the screw, the material will be gradually compressed, mixed, plasticized, and finally formed in a molten state through the mold.
In this process, the control of the screw temperature is particularly important. Too high a temperature can easily lead to material degradation.
In addition, the screw speed should be appropriate. Too fast a speed will lead to incomplete plasticization of the material, and too slow a speed may cause material degradation.
PVC melt is extruded through a specific mold, initially shaped, and then enters the cooling water tank, where it is quickly cooled by cold water to complete solidification and final shaping.
During the cooling and shaping process, the cooling speed needs to be reasonably controlled. Cooling too quickly may cause excessive force on the product, causing warping or cracking; cooling too slowly will affect production efficiency and molding effects.
Secondly, it is also important to reasonably control the temperature of the water tank. The water tank temperature needs to be maintained at a suitable temperature value to prevent watermarks or deformation on the product surface.
After cooling in the water tank, the PVC products are pulled at a constant speed by the traction machine, and then cut by the cutting machine according to the set length.
This process requires the traction speed to match the extrusion speed. Too fast or too slow will affect the dimensional accuracy and surface quality of the product.
During the product-cutting process, the accuracy of the cutting length and the flatness of the incision must be guaranteed.
PVC products need to undergo subsequent processing after cutting, such as surface treatment, punching, printing, etc. Taking PVC wallboard as an example, its surface process usually adopts PVC coating or a thermal transfer process.
When PVC products need heat treatment or surface coating, the processing temperature needs to be controlled within the allowable range of the material to avoid material deformation or surface damage.
In addition, after the surface coating or punching process is completed, PVC products also need to be measured in size, tested in surface quality, tested in mechanical properties, etc. to ensure that they meet the final design requirements.
Qualified finished products will be cleanly packaged and put into storage according to specific specifications, waiting for outbound or shipment.
The packaging materials should be moisture-proof and dust-proof to ensure that the products are not damaged during transportation and storage.
In addition, the finished products should be stored in a dry and ventilated warehouse, avoiding direct sunlight and humid environments to prevent aging or deformation of PVC products.
The above content is the main process and operating precautions of the PVC extrusion process. Each process requires precise control and strict management to ensure the final product quality and performance of PVC products.
