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Differences in Injection Molding Processes between ABS and Nylon Materials
Learn the key differences between ABS and nylon injection molding processes, including melting temperatures, cooling rates, and material properties. Discover which plastic is best for your project needs.
Shanghai Yunyan Prototype & Mould Manufacture Factory has very rich experience in injection molding so this time we discuss the injection process between NYLON and ABS difference .
There are significant differences in the injection molding process between ABS (acrylonitrile butadiene styrene copolymer) and nylon (polyamide, PA), mainly due to their different material properties (such as flowability, moisture absorption, melting point, etc.). The specific differences are as follows:
1. Raw material pretreatment
ABS：
Low moisture absorption (usually moisture content<0.2%), generally does not require strict drying, only when the environmental humidity is extremely high or the product requires high surface quality (such as high gloss parts), it needs to be dried at 80-90 ℃ for 2-4 hours to avoid bubbles or silver lines during molding.
Nylon (PA):
Highly hygroscopic (especially PA6, PA66), it is easy to absorb water in the air, leading to an increase in moisture content (exceeding 0.3% will seriously affect molding). Must be strictly dried:
Drying temperature: PA6 is 80-90 ℃, PA66 is 100-110 ℃;
Drying time: 4-8 hours (adjusted according to humidity). It is necessary to use a hot air circulation oven or a dehumidification dryer to ensure a moisture content of less than 0.1%. Otherwise, it may cause hydrolysis of the melt, decrease in product strength, and the appearance of bubbles or silver wires on the surface.
2. Molding temperature
ABS：
Material barrel temperature: 180~250 ℃ (molds with smaller main channels or gates need to be higher, about 220~250 ℃);
Nozzle temperature: slightly lower than the temperature in the front section of the barrel (200-230 ℃) to avoid melt decomposition;
Mold temperature: 50-80 ℃ (increasing the mold temperature can improve the surface gloss and internal stress of the product, and reduce warping).
Nylon (PA):
Barrel temperature: Depending on the type, PA6 is 230-260 ℃, PA66 is 260-290 ℃, and high-temperature resistant models (such as PA46) can reach over 300 ℃;
Nozzle temperature: close to the temperature of the front section of the material cylinder (to prevent blockage caused by solidification of the melt);
Mold temperature: relatively high (60~90 ℃ for PA6 and 80~120 ℃ for PA66), due to the fast crystallization rate of nylon. A higher mold temperature can reduce internal stress, improve crystallization uniformity, and avoid product brittleness or deformation.
3. Injection pressure and speed
ABS：
Medium liquidity, moderate injection pressure (60-100MPa);
Injection speed: It can be fast (medium high speed), which is conducive to filling complex cavities and reducing weld lines, but too fast speed may cause poor exhaust (resulting in burning).
Nylon (PA):
The melt has good fluidity (especially at high temperatures), but solidifies quickly, requiring high injection pressure (80-140MPa) to ensure rapid filling of the mold cavity (avoiding incomplete filling);
Injection speed: It is recommended to be fast (high speed). Due to the fast cooling speed of nylon, rapid filling can reduce surface defects (such as ripples), but it needs to be accompanied by good exhaust design (to prevent high-temperature melt from being sucked into the air and causing burning).
4. Pressure holding and cooling
ABS：
The holding time is relatively long (due to the low and uniform shrinkage rate, about 0.4%~0.7%), and the holding pressure is 50%~70% of the injection pressure to prevent the product from shrinking and sinking;
The cooling time is moderate (usually 10-30 seconds depending on the thickness of the product), and insufficient cooling can easily lead to warping.
Nylon (PA):
High shrinkage rate (PA6 about 1.5%~2.5%, PA66 about 1.5%~2%) and obvious crystal shrinkage require higher holding pressure (60%~80% of injection pressure) and longer holding time to reduce shrinkage depression;
The cooling time is relatively long, as crystallization requires time and slow cooling is necessary to ensure crystal stability (otherwise deformation may occur due to internal stress). If necessary, annealing treatment (heating in hot water or oven to eliminate stress) should be carried out.
5. Key points of mold design
ABS：
High precision is required for the mold (due to small shrinkage and good dimensional stability), and the sprue can be designed as a side sprue, point sprue, etc. The runner can be slightly thinner;
The exhaust requirements are moderate, just avoid trapping air.
Nylon (PA):
Due to good fluidity, the runner and sprue can be designed to be smaller (such as a sprue), but the size changes caused by crystal shrinkage need to be considered, and the mold cavity size needs to reserve shrinkage;
High exhaust requirements (fast melt flow rate, easy to be sucked into air), it is necessary to add exhaust grooves (depth 0.02~0.05mm) at the weld lines and corners;
The mold needs a good temperature control system (such as a heating rod) to ensure stable mold temperature.
We will get conclusions after the comparison aboves as below
The ABS molding process is more “loose” (low moisture absorption, moderate temperature and pressure), suitable for products with complex structures and high surface requirements; Nylon requires strict control of drying, high temperature and high pressure, rapid filling, and sufficient pressure cooling, making it more suitable for wear-resistant and high-strength components, but the process control is more difficult.
