Weilinna modified plastic knits today share the characteristics and processing requirements of
Polyamide Nylon 66.
Typical application range:
Compared with PA6, PA66 is widely used in the automotive industry, instrument housings and other products with impact resistance and high strength requirements.
Chemical and physical properties:
PA66 has a high melting point. It is a semi crystalline crystalline material. PA66 can also maintain strong strength and stiffness at higher temperatures. PA66 still has hygroscopicity after molding, and its degree mainly depends on the composition of materials, wall thickness of products and environmental conditions. In product design, the influence of moisture absorption on the geometric stability of the product must be considered. In order to improve the mechanical properties of PA66, modifiers are often added. Glass fiber is the most common additive. Sometimes synthetic rubber, such as EDPM and SBR, is added to improve impact resistance. The viscosity of PA66 is low, so its fluidity is good (but not as good as PA6). This property can be used to process very thin components. Its viscosity is very sensitive to temperature changes. The shrinkage of PA66 is 1-2%, and the shrinkage can be reduced to 0.2-1% by adding glass fiber additive. The shrinkage rate has a large difference in the process direction and the vertical direction of the process. PA66 is resistant to many solvents, but is less resistant to acids and other chlorinating agents. The process conditions of the injection mold are as follows:
Drying: If the material is sealed before processing, it is unnecessary to dry. If the storage container is opened, it is recommended to dry it in hot air at 85 ℃. If the humidity is greater than 0.2%, vacuum drying at 105 ℃ for 12h is also required.
Melting temperature: 260-290 ℃, 275-280 ℃ for products added with glass fiber. The melting temperature shall not be higher than 300 ℃.
Mold temperature: 80 ℃ is recommended. The mold temperature affects the crystallinity, which will affect the physical properties of the product. For thin-walled plastic parts, if the mold temperature is lower than 40 ℃, the crystallinity of the plastic parts will change with time. In order to maintain the geometric stability of the plastic parts, annealing treatment is required.
Injection pressure: usually 750-1250bar, depending on material and product design.
Injection rate: high speed (slightly lower for reinforced materials).
Runner and gate: Since the setting time of PA66 is very short, the gate position is very important. The gate aperture shall not be less than 0.5t. If hot runner is used, the gate size should be smaller than that of conventional runner, because hot runner can help prevent premature solidification of materials. If submerged gate is used, the minimum diameter of the gate shall be 0.75 mm.
