Nylon material processing techniques and precautions!

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Requirements for molding equipment and molds due to processing: For nylon molding, it is important to prevent the \"spray phenomenon at the nozzle,\" which is why self-locking nozzles are generally used for processing nylon materials. Products and Molds 1. Wall thickness of products: The flow ratio for nylon is between 150 and 200. The wall thickness of nylon products should be no less than 0.8 mm, with values typically ranging from 1 to 3.2 mm. Moreover, the shrinkage of the products is related to their wall thickness; the thicker the wall thickness, the greater the shrinkage. 2. Venting: The flash value for nylon resin is around 0.03 mm, so the vent slots should be kept below 0.025 mm. 3. Mold temperature: For molds where the product walls are thin and difficult to shape, or where a high degree of crystallinity is required, heating control is used; whereas for products that need to have a certain level of flexibility, cold water is used for temperature control. Molding process of nylon – Barrel temperature. Since nylon is a crystalline polymer, it has a distinct melting point. The barrel temperature chosen for injecting nylon resins depends on the properties of the resin itself, the equipment used, and the shape of the final product. Generally, the melt temperature for nylon 6 is at least 225°C, while that for nylon 66 is 260°C. *Due to its poor thermal stability, nylon should not remain in the barrel at high temperatures for long periods of time, to avoid discoloration and yellowing of the material. Additionally, because nylon has good fluidity, it flows rapidly once the temperature exceeds its melting point. Injection pressure: Nylon melts have low viscosity and good flowability, but they cool down rapidly; this can lead to defects in products with complex shapes or thin walls. Therefore, a higher injection pressure is still required. Usually, when the pressure is too high, the product will experience flash issues ； If the pressure is too low, the product may develop defects such as wrinkles, bubbles, visible weld marks, or insufficient volume. For most nylon grades, the injection pressure should not exceed 120 MPa; a value in the range of 60–100 MPa is generally sufficient to meet the requirements of most products. As long as the product does not have defects such as bubbles or dents, it is not necessary to use a high holding pressure, as this could lead to increased internal stresses in the product. Injection speed: For nylon, a faster injection speed is beneficial, as it helps to prevent wrinkles and insufficient filling that can occur due to too rapid cooling. A fast injection speed has little significant impact on the properties of the product. Mold temperature: Mold temperature has a certain influence on crystallinity and molding shrinkage. A higher mold temperature leads to increased crystallinity, as well as improved wear resistance, hardness, and elastic modulus; it also reduces water absorption and increases the molding shrinkage of the product ； Materials with low mold temperatures exhibit low crystallinity, good toughness, and high elongation. Precautions for molded nylon: 1. Recycled material should be used no more than three times to avoid discoloration of the products or a sharp decline in their mechanical and physical properties; its usage level should be kept below 25%. Excessive use can cause fluctuations in the processing conditions. The recycled material must be dried before being mixed with new material. 2. Safety Instructions: When starting up a nylon resin processing machine, it is necessary to first increase the temperature of the nozzle, and then heat the feed barrel. If the nozzle becomes blocked, never face the nozzle orifice, to avoid the sudden release of the melt inside the barrel due to pressure buildup, which could pose a danger. 3. Use of release agents: Using a small amount of release agent can sometimes help improve or eliminate defects such as bubbles. For releasing nylon products from molds, zinc stearate and white oil can be used; they can also be mixed together to form a paste. When using these substances, it is necessary to apply them in small amounts and evenly to avoid defects on the surface of the products. 4. When shutting down the machine, empty the screw to prevent it from breaking during the next production cycle.