Plastic mesh tells about the injection molding process of PA66

Vacuum drying: temperature °C 95-105 time 6-8 hours.

Hot air drying: temperature °C 90-100 time about 4 hours.

Crystallinity: Except for transparent nylon, nylon is mostly crystalline high polymer with high crystallinity. The tensile strength, wear resistance, hardness and lubricity of the product are improved, and the thermal expansion coefficient and water absorption tend to decrease, but Detrimental to transparency and impact resistance. The mold temperature has a great influence on the crystallization, the mold temperature is high, the crystallinity is high, and the mold temperature is low and the crystallinity is low.

Shrinkage ratio: Similar to other crystalline plastics, nylon resin has a large shrinkage rate. Generally, nylon shrinkage has the largest relationship with crystallization. When the crystallinity of the product is large, the shrinkage of the product will also increase, and the mold temperature will be lowered during the molding process. Large injection pressure / lower material temperature will reduce shrinkage, but the internal stress of the product will increase deformation. PA66 shrinkage rate is 1.5-2%.

Molding equipment: When molding nylon, the main thing is to prevent "the casting phenomenon of the nozzle". Therefore, the self-locking nozzle is generally used for the processing of nylon material.

Second, the molding process of nylon

Barrel temperature

Since nylon is a crystalline polymer, the melting point is obvious. The temperature of the cylinder selected for the nylon resin during injection molding is related to the properties of the resin itself, the shape factor of the equipment and the product, and the nylon 66 is 260 °C. Because nylon has poor thermal stability, it is not suitable for high temperature to stay in the barrel for a long time, so as to avoid discoloration and yellowing of the material. At the same time, because nylon has good fluidity, the temperature will flow rapidly after the temperature exceeds its melting point.

Injection pressure

Nylon melt has low viscosity and good fluidity, but the condensation speed is fast. It is prone to insufficient problems in products with complicated shapes and thin wall thickness, so high injection pressure is still required.

Usually the pressure is too high, the product will have overflow problems; if the pressure is too low, the product will produce defects such as ripples, bubbles, obvious weld marks or insufficient products. The injection pressure of most nylon varieties does not exceed 120MPA, generally 60-100MPA. The selection within the range is to meet the requirements of most products. As long as the product does not have defects such as bubbles and dents, it is generally undesirable to use a higher pressure holding pressure to avoid an increase in stress in the product. Injection speed For nylon, the injection speed is fast, and it can prevent the ripple caused by the excessive cooling rate and the problem of insufficient filling. The effect of fast injection speed on the performance of the product is not outstanding.

Mold temperature

The mold temperature has a certain influence on the crystallinity and the molding shrinkage rate. The high mold temperature has high crystallinity, the wear resistance, the hardness, the elastic modulus increase, the water absorption decreases, the molding shrinkage rate of the product increases, and the low mold temperature has low crystallinity. Good toughness and high elongation.