All manufacturers of nylon products have such a problem: How much can the low temperature resistant PA66 plastic be super tough and cold in the north? If your product structure is not complicated, the toughening agent can be added to 30-35%; it can reach minus 30-40°; PA66 cold resistance is almost 5-10 degrees lower than PA6; PA66 plus 30% glass fiber heat distortion temperature theoretically It is said that 220 ° C actually reaches 200 ° C should be no problem, will not be deformed. PA6 plus 30% glass fiber heat distortion temperature 170-180 °C. When the injection is taken, the temperature is generally 200 ° C, and the state of melting. This is also about whether the material is new, and the viscosity. But it is about the value of this range. The low temperature state is that the product is relatively brittle, so add a toughener.
Low temperature resistant PA66 plastic is a semi-crystalline-crystalline material. Cold-resistant PA66 plastics maintain strong strength and stiffness at higher temperatures. PA66 plastics are still hygroscopic after molding, the extent of which depends primarily on the composition of the material, the wall thickness and the environmental conditions. When designing a product, it is important to consider the effect of hygroscopicity on geometric stability. In order to improve the mechanical properties of PA66, various modifiers are often added. Glass is the most common additive, and sometimes synthetic rubber is added to improve impact resistance. PA66 plastics are less viscous and therefore have good fluidity (but not as good as PA6). This property can be used to machine very thin components. Its viscosity is sensitive to temperature changes. The shrinkage of PA66 is between 1% and 2%. The addition of glass fiber additives can reduce the shrinkage to 0.2%~1%. The shrinkage ratio is large in the flow direction and in the direction perpendicular to the flow direction.
The thermal melting point of PA66 plastic is the temperature at which the crystal is melted. For the crystalline polymer PA66 plastic, it shows a clear melting point. According to the test method used, the melting point fluctuates within the range of 259-267 °C. The melting point of PA66 plastics, usually measured by differential thermal analysis, is 264 °C. If the temperature at which the volume expansion coefficient shows the maximum value is taken as the melting point, the melting point temperature of nylon-66 is 246 to 263 °C. Close to the theoretical melting temperature of 259 ° C.
Drying treatment of injection molding properties of PA66 plastic: If the material is sealed before processing, there is no need to dry. However, if the storage container is opened, it is recommended to dry it in hot air at 85C. If the humidity is greater than 0.2%, it is also necessary to carry out vacuum drying at 105 C for 12 hours.
Low temperature resistant PA66 plastic injection molding process introduction:
Melting temperature: 260~290C. The product for glass additives is 275~280C. The melting temperature should be avoided above 300C. Mold temperature: 80C is recommended. The mold temperature will affect the crystallinity, which will affect the physical properties of the product. For thin-walled plastic parts, if a mold temperature lower than 40C is used, the crystallinity of the plastic part will change with time, and in order to maintain the geometric stability of the plastic part, annealing treatment is required.
Injection pressure: usually between 750 and 1250 bar, depending on material and product design.
Injection speed: high speed (slightly lower for reinforced materials).
Runners and gates: Due to the short solidification time of the cold-resistant PA66, the location of the gate is very important. The gate aperture should not be less than 0.5*t (where t is the thickness of the plastic part). If a hot runner is used, the gate size should be smaller than with a conventional runner because the hot runner can help prevent premature solidification of the material. If a submerged gate is used, the minimum diameter of the gate should be 0.75 mm.
Cold-resistant PA66 plastic application PA66 is a kind of PA series with high mechanical strength and wide application. Because of its high crystallinity, it has high rigidity and heat resistance. High-temperature electrical socket parts, electrical parts, gears, rollers, springs. Brackets, pulleys, bolts, impellers, fan blades, propellers, high pressure sealing gaskets, valve seats, oil pipes, oil storage containers, ropes, cable ties, drive belts, grinding wheel adhesives, battery boxes, wire cores, wire drawing, etc.
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