Polyamide 66 (PA66) or poly (hexamethylene adipamide), a homopolymer is a product of polymerization reaction between adipic acid, and hexamethylene diamine. Amid polyamides available commercially, it is PA66 that exhibited the maximum melting points.
PA66, a semicrystalline solid, possesses a stiffness, and strength grade maintained at a high temperature. After the molding of Nylon 66, it absorbs moisture. However, moisture retention is not comparable to that of PA6.
Moisture retention rest on the material composition, environmental factor, and wall viscosity. However, dimensional firmness and properties of PA66 are affected by the quantity of moisture retained, which is always paramount during product design.
Mechanical properties are enhanced by the introduction of different modifiers such as glass (common filler used), and elastomers that enhance the polyamide resistance.
The thickness is low, hence, it pours easily. This property enables the molding of thin materials. The viscosity is directly proportional to the temperature.
Shrinkage or reduction is in order 1 – 2%, but the reinforcement of the glass fiber condenses the shrinkage to 0.2 – 1%. PA66 is vulnerable to oxidizing agents or strong acids but forms resistance to most solvents. However, when buying PA66 for different industrial applications, it is important you contact a reputable manufacturer for your best deal.
This article considers the foremost industrial injection PA66 molding parameters for the design of your product.
Foremost Molding Parameter of Polyamide 66
Different ranges of temperature are recommended for a successful molding of polyamide. The feeding zone temperature is suggested to be maintained at 80°C, and nozzle temperature should not exceed 290°C.
The temperature parameter improves stroke operation between 35% and 65%. The module ratio and flow dimension to the wall depth ranges from 50:1 to 100:1. The feed efficiency is directly affected by feed zone temperature, however, temperature increment enables the feed to be more even.
The melting range is approximately 270~290°C, barrel temperature is maintained at 240°C and the molding process can conveniently run at 60~100°C.
Injection PA66 pressure is recommended to range from 1000 ~ 1600bar when a thin section is a process long the passage products, you can extend the pressure to 1800bar.
Due to the comparative fast contracting of the material, 50% of the injection pressure is recommended. Reducing the molding pressure reduces the internal stress of the product.
The backpressure is recommended to be regulated accurately between 20 ~ 80bar because, if the back pressure is high, the plasticization is affected due to the irregular injection swiftness. However, moderately timing injection speed is recommended.
3. Screw Speed
The screw speed is very important in the plasticizing process, thus, the recommended line speed is fixed at 1m/s. Note, it is best to set the screw speed of injection molding at a minimal level. This will help the plasticizing process to get to completion before the cooling time elapsed. The screw torque is required to be low.
Residual pallet volume is recommended between 2~6 mm, which depends on the measuring lash and screw thickness.
Injection PA66 is recommended to be dried for about 4 hours at 80 ° C unless feeds are used directly from the charging vessel. Recall, nylon 66 is an absorbent hence, it can absorb moisture. Note, any water content as low as 0.25% can affect the molding process.
When working with reinforcing nylon 66, which contains about 2.0% to 0.7% or 0.7% to 0.4% glass fiber, the temperature should be kept as low as 60 °C so that the product will cool gradually.
This slow cooling can decrease the shrinkage of the molding, which in turn improve the product performance. However, minimal internal stress and dimensional stability are recommended.
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