Polyether ether ketone (PEEK) is a high-performance thermoplastic known for its exceptional mechanical properties, chemical resistance, and ability to withstand extreme conditions. It is widely used in demanding applications across industries such as aerospace, automotive, medical, and electronics. PEEK’s durability and strength make it an ideal material for components that require precision and reliability.
Injection molding is one of the most effective manufacturing methods for producing PEEK parts. The process involves melting the PEEK granules and injecting them into a mold to create complex shapes with tight tolerances. This article explores the key aspects of PEEK plastic injection molding, including its benefits, challenges, and applications.
Understanding PEEK Material
PEEK is a semicrystalline thermoplastic characterized by its high melting point (343°C), excellent dimensional stability, and resistance to harsh chemicals and temperatures ranging from -196°C to 260°C. Its molecular structure, featuring alternating ether and ketone groups, accounts for its remarkable properties. Since its introduction in the 1970s by Victrex plc, PEEK has undergone significant improvements in manufacturing processes, making it an increasingly attractive material for demanding applications.
PEEK Material Properties Comparison
PEEK (Polyether Ether Ketone) comes in various grades, each offering distinct mechanical, physical, and processing properties.
| Property | PEEK 450G Unfilled | PEEK 90GL30 GF 30% | PEEK 450CA30 CF 30% | PEEK 150G903 Black |
|---|---|---|---|---|
| Density (g/cm³) | 1.30 | 1.52 | 1.40 | 1.30 |
| Shrinkage Rate (%) | 1.0 to 1.3 | 0.3 to 0.9 | 0.1 to 0.5 | 1.0 to 1.3 |
| Shore Hardness (D) | 84.5 | 87 | 87.5 | 84.5 |
| Tensile Strength (MPa) | 98 @ Yield | 195 @ Break | 265 @ Break | 105 @ Yield |
| Elongation (%) | 45 | 2.4 | 1.7 | 20 |
| Flexural Modulus (GPa) | 3.8 | 11.5 | 24 | 3.9 |
| Flexural Strength (MPa) | 165 | 290 | 380 | 175 |
| Drying Temperature (°C) | 150 | 150 | 150 | 150 |
| Drying Time (hrs) | 3 | 3 | 3 | 3 |
| Melt Temperature (°C) | 343 | 343 | 343 | 343 |
| Mold Temperature (°C) | 170 to 200 | 170 to 200 | 180 to 210 | 160 to 200 |
Key Observations
- Unfilled vs. Filled Grades: PEEK 450G Unfilled and PEEK 150G903 Black: Higher elongation (more elastic) but lower tensile and flexural strength. PEEK 90GL30 GF 30% and PEEK 450CA30 CF 30%: Higher tensile strength and flexural modulus but reduced elasticity.
- Strength vs. Elasticity: Filled grades offer greater strength but significantly lower flexibility, important for applications needing either rigidity or flexibility.
- Shrinkage Rates: Glass and carbon fibers reduce shrinkage, allowing for tighter tolerances in precision applications.
- Pigmented PEEK (PEEK 150G903 Black): Slightly higher tensile strength than PEEK 450G. Used for UV protection or color identification.
PEEK Injection Molding Process
PEEK plastic injection molding involves forcing molten PEEK material into a precisely designed mold, where it cools and solidifies into the desired shape. The process is highly automated and efficient, allowing for the mass production of complex parts with high consistency and accuracy.
Step 1. Material Preparation
The first step involves preparing the PEEK material, typically in the form of granules. These granules are fed into the hopper of the injection molding machine, where they are gravity-fed into a heated barrel.
Step 2. Melting and Injection
Inside the heated barrel, the PEEK granules are heated and melted by a rotating screw or plunger. As the screw advances, the molten PEEK is forced through a nozzle and injected into the mold cavity at high pressure.
Step 3. Cooling and Solidification
The mold remains cold, allowing the PEEK plastic to solidify almost immediately after filling the cavity. The cooling process is crucial as it ensures that the part retains its shape and dimensional stability.
Step 4. Ejection and Post-Processing
Once the PEEK part has fully cooled and solidified, the mold is opened, and the part is ejected. Depending on the requirements, the part may undergo further post-processing steps such as trimming, polishing, or surface treatment to enhance its appearance and functionality.
Step 5. Repeatability
The process is highly repeatable, allowing for the production of identical parts in large quantities. The mold and injection machine are designed to ensure consistent quality and precision in each cycle.
Advantages of PEEK Injection Molding
PEEK (Polyether ether ketone) plastic injection molding offers a wide range of advantages, especially for applications that demand high performance in challenging environments. Below are the key advantages of using PEEK in injection molding:
High-Temperature Resistance
PEEK can withstand continuous operating temperatures of up to 260°C (500°F) without degrading, making it an excellent choice for high-heat applications. This allows PEEK-molded components to perform reliably in industries like aerospace, automotive, and oil and gas, where exposure to extreme temperatures is common.
Chemical Resistance
PEEK has outstanding chemical resistance to a wide range of acids, bases, organic solvents, and oils. This makes it suitable for environments where parts are exposed to corrosive chemicals, such as in chemical processing equipment, pumps, and valves.
Wear and Friction Resistance
PEEK has low friction and excellent wear resistance, which is why it’s often used in components that require long-lasting, smooth operation, such as bearings, bushings, and gears. The material’s low coefficient of friction reduces the need for lubrication, contributing to longer part life and lower maintenance costs.
Biocompatibility
PEEK is biocompatible and FDA-approved, making it a popular choice for medical implants and devices. It can be sterilized using autoclaving, gamma radiation, and other methods, ensuring safety and durability in medical environments. Additionally, PEEK is radiolucent, meaning it does not interfere with imaging techniques like X-rays or MRIs.
Low Moisture Absorption
PEEK has very low moisture absorption, even in high-humidity environments. This property helps maintain dimensional stability and prevents the degradation of mechanical properties, which is essential for precision parts that must maintain tight tolerances.
Lightweight Alternative to Metals
PEEK’s strength-to-weight ratio allows it to replace metals in many applications, offering a lighter solution without sacrificing durability. This can lead to weight reductions in products, which is particularly beneficial in industries such as aerospace and automotive, where weight savings can improve fuel efficiency and performance.
Applications of PEEK Plastic Injection Molding
PEEK injection molding is used to manufacture a variety of high-performance components in several industries:
- Aerospace connectors
- Bearings
- Bushings
- Gears
- Seals
- Medical implants
- Surgical instruments
- Electrical connectors
- Insulators
- Pump components
- Valves
- Automotive transmission parts
- Fuel system components
- Semiconductor components
- Oil and gas exploration equipment
Design Guidelines for PEEK Plastic Injection Molding
Part designers who follow PEEK plastic injection molding design guidelines can improve manufacturability, reduce costs, and minimize defects. Key considerations include:
- Wall Thickness: Recommended wall thickness is between 1.0 and 3 mm. Uniform thickness is ideal, but gradual transitions between different thicknesses are acceptable.
- Radii: Avoid sharp edges and corners. A minimum radius of 25% of the wall thickness helps prevent stress concentrations.
- Draft Angle: Apply draft angles between 0.5° and 2° for easy part ejection. Textured parts require more draft, while smoother parts require less.
- Gate Location: Proper gate placement ensures even material flow and reduces stress on parts.
- Part Tolerance: PEEK tolerances can be as tight as 0.05%. Unfilled PEEK shrinks 1-1.8%, while filled PEEK shrinks up to 0.9%.
- Cooling Time: Adequate cooling time is critical to avoid warping and ensure dimensional stability.
How Much Does PEEK Injection Molding Cost?
PEEK injection molding costs vary based on factors like material grade, tooling, and production volume. Material costs range from $60 to $120 per kg. Tooling can cost $5,000 to $100,000. Per-part costs are typically $20 to $100 for low-volume and $5 to $30 for high-volume production.
PEEK Plastic Injection Molding With BOYI
BOYI specializes in high-performance PEEK plastic injection molding, offering precision and reliability for demanding applications. Our advanced machinery and expert team ensure that every part meets tight tolerances and intricate designs.
Our rapid prototyping services facilitate quick turnaround times for prototypes and production runs. We prioritize quality with rigorous testing and quality checks, ensuring that every part performs reliably and meets the highest standards. Please contact one of our knowledgeable applications engineers at [email protected]
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FAQ
Compared to PTFE, PEEK has higher mechanical strength and thermal stability. When compared to PPS, PEEK has better chemical resistance and can withstand higher temperatures, making it more suitable for extreme environments.
Barrel temperatures typically range from 350°C to 400°C (662°F to 752°F), and mold temperatures are usually set between 200°C and 250°C (392°F to 482°F).
PEEK pellets should be thoroughly dried before processing to remove any moisture, which can cause defects. Drying typically involves heating the pellets at around 150°C (302°F) for several hours.
High-temperature steel molds or specially coated molds are used to withstand the high processing temperatures required for PEEK. The molds must be capable of maintaining precise temperature control.
Yes, PEEK can be used for prototyping, but due to its high cost, it is typically used in prototyping only when the final application demands its high-performance properties. For preliminary testing, other materials may be used to reduce costs.
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
