The chemical and physical properties of PA6 are very similar to PA66, however, PA6 has a lower melting point and a wide temperature range. Its impact resistance and anti-solubility better than PA66, but also more hygroscopic. Because many of the quality characteristics of plastic parts are subject to hygroscopicity, so take full account of this when designing your product with PA6. In order to improve the mechanical properties of PA6, often add a variety of modifiers. Glass is the most common additive and is sometimes added to elastomers such as EPDM and SBR to improve impact resistance. For products without additives, the shrinkage of PA6 is between 1% and 1.5%. Adding glass fiber additives can reduce shrinkage to 0.3% (but slightly higher in the direction perpendicular to the process). Molding shrinkage is mainly due to the material crystallinity and hygroscopicity.
Injection molding process conditions:
Drying: PA6 is very easy to absorb moisture, so dry before processing with special attention. If the material is supplied with water-resistant material, the container should be kept closed. If the humidity is greater than 0.2%, it is recommended to dry in hot air above 80C for 16 hours. If the material has been exposed to air for more than 8 hours, it is recommended to carry out vacuum drying at 105C for more than 8 hours.
Melting temperature: 230 ~ 280C, for enhanced varieties of 250 ~ 280C.
Mold temperature: 80 ~ 90C. Mold temperature significantly affects the degree of crystallinity, which in turn affects the mechanical properties of the part.
The crystallinity is important for the structural components, so a mold temperature of 80-90C is recommended. For thin-walled, long-range plastic parts also recommend the application of higher mold temperature. Increase the mold temperature can increase the strength and stiffness of plastic parts, but reduces the toughness. If the wall thickness is greater than 3mm, it is recommended to use 20 ~ 40C low temperature mold. For glass reinforcement mold temperature should be greater than 80C.
Injection pressure: Generally between 750 ~ 1250bar (depending on material and product design).
Injection speed: High speed (slightly lower for reinforced materials).
Runners and gates: Due to the short setting time of the PA6, the position of the gate is very important. Gate aperture not less than 0.5 * t
(Where t is the plastic thickness). If hot runner is used, gate size should be smaller than with conventional runners because hot runner can help prevent material from premature solidification. If submerged gates are used, the minimum gate diameter should be 0.75mm.
PA66 has a higher melting point in polyamide materials. It is a semi-crystalline - crystalline material. PA66 also maintains strong strength and stiffness at higher temperatures. PA66 is still hygroscopic after forming, the extent of which depends mainly on the composition of the material, the wall thickness and the environmental conditions. In product design, we must consider the hygroscopicity on the geometric stability.
In order to improve the mechanical properties of PA66, often add a variety of modifiers. Glass is the most common additive and is sometimes added to elastomers such as EPDM and SBR to improve impact resistance.
PA66 has low viscosity and therefore good fluidity (but not as good as PA6). This property can be used to process very thin components.
Its viscosity is sensitive to temperature changes. The shrinkage rate of PA66 is between 1% ~ 2%. The addition of glass fiber additives can reduce the shrinkage to 0.2% ~ 1%. Shrinkage in the flow direction and the flow direction of the vertical difference is larger.
PA66 is resistant to many solvents but less resistant to acids and some other chlorinating agents.
Injection molding process conditions:
Drying: If the material is sealed before processing, then there is no need to dry. However, if the storage container is opened, it is advisable to dry it in 85C hot air. If the humidity is greater than 0.2%, also need to 105C, 12 hours of vacuum drying.
Melting temperature: 260 ~ 290C. The product of glass additives for 275 ~ 280C. Melting temperature should be avoided above 300C.
Mold temperature: Recommended 80C. Mold temperature will affect the degree of crystallinity, and crystallinity will affect the physical properties of the product. For thin-walled plastic parts, if you use a mold temperature of less than 40C, the plasticity of the plastic parts will change over time, in order to maintain the geometric stability of plastic parts, the need for annealing.
Injection pressure: usually 750 ~ 1250bar, depending on the material and product design.
Injection speed: high speed (for reinforced materials should be slightly lower).
Runner and gate:
Due to the short setting time of the PA66, the position of the gate is very important. Gate aperture not less than 0.5 * t (where t is the plastic thickness). If hot runner is used, gate size should be smaller than with conventional runners because hot runner can help prevent material from premature solidification. If using submerged gates, the minimum gate diameter
It should be 0.75mm.
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