PA66,PA6

PA6 Plastics Description:
PA6 is a commonly used engineering plastics,and it has a wide range of industrial applications.

Typical applications:
Due to the good mechanical strength and stiffness ,PA 6 is widely used in structural parts. Also it has good wear-resistance characteristics for the manufacture of bearings.

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Injection molding process :

 

  • 1. Drying treatment:

PA6 is very easy to absorb moisture, so it need drying process before injection molding.
If the material is supplied in watertight packaging, the container shall be kept closed.
If the humidity is greater than 0.2%, 80 C or more is recommended in hot air drying for 16 hours.
If the material has been exposed to air for more than 8 hours, the proposed 105 C, 8 hours vacuum drying need.

  • 2. Melting temperature:

230 ~ 280 ℃, for the enhanced PA6 with 250 ~ 280 ℃.

  • 3. Mold temperature:

Mold temperature is 80 to 90 C. The mold temperature significantly affects the crystallinity, which in turn affects the mechanical properties of the plastic part.
Crystallinity is important for structural parts, so a mold temperature of 80-90 ° C is recommended.
For thin-walled, long-running parts, a higher mold temperature is also recommended.
Increasing the mold temperature increases the strength and rigidity of the part, but it reduces the toughness.
If the wall thickness is greater than 3mm, it is recommended to use 20 ~ 40 ℃ low temperature mold.
For glass reinforcements the mold temperature should be greater than 80 ° C.

  • 4. Injection pressure:

Typically between 750 and 1250 bar (depending on material and product design).

  • 5. Injection speed:

High speed (slightly reduced for reinforced materials).

  • 6. Runner and gate:

Because the solidification time of PA6 is very short, the position of the gate is very important. Gate diameter should not be less than 0.5 × t (where t is the plastic thickness).
If a hot runner is used, the gate size should be smaller than a conventional runner, since the hot runner can help prevent the early solidification of the material. If a submerged gate is used, the minimum diameter of the gate shall be 0.75 mm.

Chemical and physical properties:

PA6 chemical and physical properties is very similar with PA66 , however, it has low melting point and the process temperature range is very wide.
Its impact resistance and anti-solubility is better than that of PA66, but with the higher hygroscopicity .
Since many of the quality characteristics of plastic parts are subject to the impact of moisture absorption, this point should be taken into full consideration when design PA6 products.
In order to improve the mechanical properties of PA6 part, a variety of modifiers are often added.
Glass fabric is the most common additive, and sometimes in order to improve the impact resistance it also need add synthetic rubber, such as EPDM and SBR.
For PA6 products without additives, its shrinkage is between 1% and 1.5%.
Glass fabric can be added to reduce the shrinkage rate to 0.3% (but the direction and the process is even slightly higher vertical direction).
Shrinkage of the injection molding is mainly affected by the material crystallinity and moisture absorption. The actual shrinkage is related with the plastic part design, wall thickness and other process parameters.

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Advantages and Disadvantages of PA(nylon)6 and PA66(nylon) with additives

  • 1. nylon 6 with glass fabric

Advantages: good dimensional stability, thermal stability, wear resistance, high mechanical strength, excellent chemical resistance;

Material applications:  used for electric tools, fishing gear, auto parts, machinery parts, office accessories and so on.

Molding Challenge: Under normal circumstances, PA+GF products prone to have glass fiber rich surface. Mold can be modified to improve the mold venting, and increase the mold temperature. In addition, to maintain high pressure and low speed, increase injection pressure, reduce the injection speed, increase the screw speed and back pressure could solve the problem of glass fiber rich surface.

  • 2. Flame retardant nylon 6 with glass fabric

Advantages: small density, good gloss, better toughness, better heat resistance

Material applications: used for connectors, electronic components, fuse boxes, switch electrical terminals, communications equipment.

injection molding challenges: for narrow and long products, if the gate position or mold temperature is not appropriate,it prone to have the both ends of the arch deformation.This can be modified by changing the gate to the end of the product, not in the middle, or adjusting the mold temperature and improving the accuracy of mold .

  • 3 Super-Tough and cold-resistance nylon 6

Advantages:heavy load, impact resistance, high / low temperature, excellent chemical resistance

Material applications: can be used for casters and accessories, textile equipment, sports equipment, railway components.

Molding Challenge: poor mold finish and inappropriate material temperature and mold temperature  would lead to poor injection part surface. The poor surface can be appropriately improved by adjusting the mold temperature ,injection pressure and injection volume.

  • 4. Flame-retardant nylon 6

Advantages: small density, good gloss, better toughness, better heat resistance

Material applications: used for connectors, electronic components, fuse boxes, switch electrical terminals, communications equipment.

injection molding challenges: for narrow and long products, if the gate position or mold temperature is not appropriate,it prone to have the both ends of the arch deformation.This can be modified by changing the gate to the end of the product, not in the middle, or adjusting the mold temperature and improving the accuracy of mold .

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PA66 advantages and disadvantages

  • Glass fiber PA66

Advantages: excellent impact resistance, excellent heat  resistance, resistance to oil.

Material applications: used for gears, water guns, winter sports equipment,  mechanical parts.

injection molding challenges: the sparkling silver stripes would occur on the product surface or near the gate , it is due to the material containing moisture ,too much shearing or rapid cooling . improving the mold temperature and injection pressure, increasing the flow channel and gate size, reducing the shear could solve the phenomenon of silver stripes products.

  •   Flame retardant PA66 with glass fabric

Advantages: small density, high gloss, excellent toughness,  heat resistance

Applications: used for connectors, electronic components, fuse boxes, switch electrical terminals, communications equipment.

molding challenges: for narrow and long products, if the gate position or mold temperature is not appropriate,it prone to have the both ends of the arch deformation.This can be modified by changing the gate to the end of the product, not in the middle, or adjusting the mold temperature and improving the accuracy of mold .

  • Flame retardant PA66

Advantages: small density, high gloss, excellent toughness,  heat resistance

Applications: can be used for connectors, electronic components, fuse boxes, switch electrical terminals, communications equipment.

Molding challenges: for narrow and long products, if the gate position or mold temperature is not appropriate,it prone to have the both ends of the arch deformation.This can be modified by changing the gate to the end of the product, not in the middle, or adjusting the mold temperature and improving the accuracy of mold .