Differ the production process level of PC sheet manufacturers?
PC (polycarbonate) sheet is an amorphous, highly transparent thermoplastic engineering plastic with excellent physical and mechanical properties, especially excellent impact resistance, high tensile strength, bending strength, compressive strength, and low creep. It is dimensionally stable and can be used in greenhouses, industrial buildings, urban buildings and other fields.
With the continuous surge in demand for PC sheets, small and large manufacturers have sprung up like bamboo shoots after a rain. So, how should we judge the strength of these manufacturers? It mainly depends on whether the co-extrusion process used meets the standard.
Unique engineering exterior
Co-extrusion molding is currently the most widely used processing method in PC sheet production. The extrusion process can be divided into two stages: the first stage is to plasticize the solid plastic, and under pressure, it passes through a special form of die to become a continuum similar to the shape of the mouth pattern; the second stage is to use Appropriate treatment methods make the extruded continuum lose its plastic state and become solid, that is, the desired product.
Generally, extrusion molding can continuously produce semi-finished profiles, pipes, sheets, films, etc. Multi-layer sheet extrusion generally means that two-layer, three-layer or even more sheets are layered together in a certain way to form a multi-layer sheet, so it also has advantages that some single-layer sheets do not have. In the co-extrusion process, several criteria are the key to distinguish the pros and cons of the production process.
Factory raw material storage area
In the process of processing PC sheets, the drying and degassing of materials is an essential step. Experience has proved that in the sheet extrusion process, degassing is of great help to increase the yield, even in high humidity areas, degassing is necessary. In addition, if the pellets are not well preserved and the water content is large, drying is also an essential step. However, for the protective layer of weather-resistant material with anti-ultraviolet function, degassing treatment is not necessary, because the ultraviolet absorber is a volatile substance, but the pre-drying step cannot be omitted.
For the main extruder, during processing, the melt temperature at the end of the screw is between 270°C and 300°C. According to the principle of temperature control, from the beginning of the hopper to the end of the nozzle, the temperature of the barrel decreases from 300°C to 270°C, and drops to 250°C-260°C in the degassing zone. Basically, the barrel temperature of the co-extruder is about 20°C lower than the temperature of the base material.
Factory production area
The temperature of the subsequent device
For subsequent devices, such as filter screens, melt pumps, co-extrusion adapters, and sheet die heads, all should match the temperature of the last section of the barrel as much as possible.
Temperature control equipment temperature
For thin multilayer sheets, temperature control equipment is essential. After the sheet is shaped, the sheet needs to be reheated to 130°C~140°C by an infrared heating device to avoid stress and distortion.
The maximum pulling speed of the multilayer sheet is usually determined by the shaping process, and at the same time depends on the mass or thickness per unit area.
Imported production equipment
Of course, these standards are just the basis for the production of PC sheets. If you want to process high-quality PC sheets, you need to optimize the processing methods. Usually the work that needs to be done to optimize the process is: keep the melt temperature as low as possible; keep the accuracy of the upper and lower ends of the nozzle: keep the space between the nozzle and the shaping mold to a minimum; keep the partial vacuum of the first shaping mold as much as possible: keep the shaping area The lowest possible temperature.
In addition, at the end of production, the extruder should be idling, and the temperature of all equipment should be maintained between 160°C and 170°C. If cleaning is required after the end of production, it is best to use high-viscosity PE on the extruder, which is conducive to the subsequent cleaning work.