Views: 0 Author: Site Editor Publish Time: 2024-09-29 Origin: Site
Drying: PEEK resin is hygroscopic. Before processing, the raw materials need to be dried. It is generally recommended to dry them at a temperature of 150 - 180℃ for 3 - 4 hours to remove moisture. The presence of moisture may lead to hydrolysis and bubble problems during processing, which will affect the quality and performance of the sheet. For example, if there are bubbles in the sheet, its mechanical properties will decline and it is prone to rupture under pressure.
Screening: Ensure the purity and quality of the raw materials. Carefully check whether there are impurities, foreign substances, or different types of resins mixed in the raw materials. Because impurities may become stress - concentration points and reduce the strength and toughness of the PEEK sheet.
Extrusion Molding Temperature: If the extrusion process is used to produce PEEK sheets, the temperature setting of each section of the extruder is crucial. Generally, the temperature gradually increases from the feeding section to the die. The temperature of the feeding section can be set at 360 - 380℃, and the die temperature is usually around 400 - 420℃. Precise temperature control can ensure that the resin is uniformly melted and extruded. If the temperature is too high, it may cause the resin to decompose, generate gas, and lead to pores inside the sheet; if the temperature is too low, the resin's fluidity will be poor, extrusion will be difficult, and the sheet surface will be uneven.
Hot - Pressing Molding Temperature: For the hot - pressing process, the appropriate temperature range is 380 - 400℃. This temperature range helps the PEEK resin to fully flow and compact inside the mold to form a uniform sheet structure. If the temperature is too high, the sheet surface may oxidize and change color, affecting the appearance and performance; insufficient temperature will result in insufficient density of the sheet and reduced mechanical properties.
Extrusion Pressure: During extrusion, the extrusion pressure should be reasonably adjusted according to the thickness and width requirements of the sheet. Generally, the extrusion pressure is between 10 - 30MPa. Appropriate pressure can ensure the smooth extrusion of the resin and enable the sheet to have good dimensional accuracy and density. Excessive pressure may lead to increased wear of the mold and may also cause residual stress inside the sheet; too little pressure cannot guarantee the quality and dimensional stability of the sheet.
Hot - Pressing Pressure: During hot - pressing molding, the pressure is usually controlled at 5 - 15MPa. Sufficient pressure enables the PEEK resin to fully fill every corner in the mold and ensures the compactness of the sheet. Inappropriate pressure may lead to problems such as delamination and uneven thickness of the sheet.
Mold Design: The structure and size of the mold should be designed according to the target size and shape of the PEEK sheet. The runner of the mold should be designed so that the molten PEEK resin can be evenly distributed, avoiding situations where the local flow rate is too fast or too slow. For example, a coat - hanger - type runner can effectively improve the uniformity of resin flow.
The surface finish of the mold is required to be relatively high. Because the PEEK resin is highly viscous, a rough mold surface is likely to cause scratches and scuffs on the sheet surface, affecting the appearance and quality.
Mold Cleaning: During the production process, the mold should be cleaned regularly. Because during processing, PEEK resin may remain on the mold surface, and long - term accumulation will affect the dimensional accuracy and surface quality of the sheet. When cleaning the mold, a special mold - cleaning agent can be used, and sharp tools should be avoided to prevent damage to the mold surface.
Controlling the Cooling Rate: The PEEK sheet needs to be cooled after molding. The cooling rate should not be too fast, otherwise, large internal stresses will be generated, resulting in warping and deformation of the sheet. Generally, natural cooling or cooling under appropriate air - cooling conditions is used to allow the sheet to cool gradually. For example, when air - cooling, the wind speed is controlled at about 1 - 3m/s.
Preventing Shrinkage Deformation: Although the coefficient of thermal expansion of PEEK is small, there will still be a certain amount of shrinkage during the cooling process. When designing the mold size, this shrinkage factor should be considered and a certain amount of shrinkage allowance should be reserved. At the same time, appropriate post - treatment processes such as tempering can be used to reduce the impact of shrinkage deformation on the sheet quality.
Appearance Inspection: The produced PEEK sheets should be subjected to strict appearance inspections. Check whether there are bubbles, scratches, pits, discoloration and other defects on the surface. For sheets with appearance defects, they should be classified and processed according to the severity of the defects. Seriously defective products should be scrapped.
Dimensional Accuracy Measurement: Use calipers, micrometers and other tools to measure the thickness, length, width and other dimensions of the sheet to ensure that its dimensional accuracy meets the product standard requirements. Sheets with excessive dimensional deviations may affect their assembly and performance in subsequent applications.
Performance Testing: Test the physical and chemical properties of the sheet. Physical properties include tensile strength, flexural strength, impact strength, etc., which can be tested by universal material testing machines; in terms of chemical properties, its chemical corrosion resistance is tested. For example, after soaking the sheet in different acid - base solutions for a certain period of time, observe the performance changes of the sheet. This helps to ensure that the PEEK sheet can meet the needs of various practical application scenarios.