Process Logic of Reinforced PA6 Injection Temperature Control
Reinforced PA6 (Nylon 6 with glass fiber) is one of the most widely used engineering plastics, prized for its excellent strength, stiffness, and heat resistance in automotive components, power tools, and mechanical structural parts. Injection temperature is one of the most critical process parameters in reinforced PA6 molding—inadequate temperature settings can affect fiber distribution, crystallinity, mechanical properties, and even cause material degradation.
Recommended Reinforced PA6 Injection Temperature Range
PA6 is a semi-crystalline polymer with a melting point of 220-225°C. After glass fiber reinforcement, melt viscosity increases, requiring higher processing temperatures for flowability. The recommended barrel temperature profile for reinforced PA6 is as follows:
Rear zone (feeding): 230-250°C. Since PA6 is highly hygroscopic, the feeding zone temperature should not be too low, or moisture cannot be properly vented. Middle zone (compression): 250-270°C. The main melting and plasticizing stage; sufficient temperature here ensures uniform mixing of glass fiber and PA6 matrix. Front zone (metering): 270-290°C. Ensures uniform melt temperature. Nozzle temperature: 270-285°C. Typically 5-10°C lower than the front zone. Mold temperature: 80-120°C, recommended value 90-110°C.
Mold temperature has a decisive impact on the crystallinity and final product performance of reinforced PA6. Higher mold temperature leads to more complete crystallization, resulting in greater stiffness and heat deflection temperature, but also higher shrinkage and longer cycle time. Conversely, low mold temperature causes incomplete crystallization, poor dimensional stability, and potential post-shrinkage.
Temperature Adjustment Strategy for Different Glass Fiber Content
PA6+GF30 (30% glass fiber) and PA6+GF50 (50% glass fiber) have slightly different injection temperatures. Higher fiber content means greater melt viscosity, requiring higher injection temperatures. For PA6+GF30, the recommended barrel temperature range is 240-280°C with melt temperature controlled at 275-295°C. PA6+GF50 temperatures should be 5-10°C higher, with barrel temperatures reaching up to 290-300°C. Note: exceeding 310°C causes significant thermal degradation of the PA6 matrix, producing gel and black spots.
Key Temperature Control Points for Reinforced PA6 Injection
Reinforced PA6 is extremely moisture-sensitive. Even trace moisture in the molten state causes hydrolytic degradation, leading to molecular weight reduction, brittleness, and silver streak surface defects. Therefore, thorough drying before injection is essential: dry at 100-120°C for 3-4 hours to bring moisture content below 0.2% (ideally below 0.1%). Using a desiccant dryer provides more reliable results.
For temperature monitoring, it is recommended to use a melt temperature probe to regularly check actual melt temperature rather than relying solely on barrel setpoints. The actual melt temperature may differ from the set temperature by 10-20°C, depending on screw speed, back pressure, and barrel temperature control strategy.
Other Critical Process Parameters for Reinforced PA6 Injection
Beyond temperature, the following parameters are crucial: Injection pressure: 800-1400 bar (depending on part complexity and fiber content); Hold pressure: 50%-80% of injection pressure; Back pressure: 5-15 bar (back pressure helps improve glass fiber dispersion uniformity); Screw speed: 30-60 rpm (excessive speed causes fiber over-shear and breakage, reducing reinforcement effectiveness); Injection speed: Medium to high speed to ensure the melt front advances quickly, avoiding uneven fiber orientation.
Temperature-Related Solutions for Common Defects
When reinforced PA6 parts show surface fiber bloom (glass fiber exposure), it can usually be improved by increasing mold temperature (to 100-120°C) and injection speed. Black spots or scorching are typically caused by excessive melt temperature or prolonged residence time—reduce barrel temperature and shorten dwell time. Warpage is related to uneven mold temperature—check the mold cooling channel design for balance.
In summary, reinforced PA6 injection temperature control is a multi-variable optimization project, requiring process engineers to fine-tune based on specific product structure, mold design, and material batches.
