Ever wondered what makes PEEK injection molding so special? This high-performance process is vital in industries like aerospace and medical. PEEK’s exceptional strength and heat resistance set it apart.
In this blog, you’ll learn about PEEK injection molding, its benefits, and its importance across various sectors.
What is PEEK Plastic?
PEEK, short for Polyether Ether Ketone, is a high-performance thermoplastic that has taken the manufacturing world by storm. But what exactly is this material, and what sets it apart from other plastics? Let's dive in and explore the fascinating world of PEEK.
Chemical Structure and Composition
At its core, PEEK boasts a unique chemical structure that gives it its remarkable properties. It belongs to the PAEK (Polyaryletherketone) family, which is known for its exceptional strength and stability. The backbone of PEEK consists of repeating units of ether and ketone groups, as shown in the image below:
This distinctive arrangement of molecules allows PEEK to maintain its integrity even under extreme conditions. It can withstand high temperatures, resist chemicals, and endure mechanical stress like no other.
Comparison with Other High-Performance Thermoplastics
When stacked up against other high-performance thermoplastics, PEEK truly shines. Take a look at this comparison table:
| Property | PEEK | PEI | PPSU | PPS |
| Tensile Strength (MPa) | 90-100 | 85-105 | 75-85 | 65-75 |
| Continuous Use Temperature (°C) | 250 | 170 | 180 | 220 |
| Chemical Resistance | Excellent | Good | Good | Excellent |
| Wear Resistance | Excellent | Good | Good | Good |
Types of PEEK
Not all PEEK is created equal. Manufacturers have developed various grades and formulations to cater to specific needs. Here's a quick rundown of the main types:
Unfilled PEEK: This is the purest form of PEEK, without any additives or reinforcements. It offers the highest level of chemical resistance and is ideal for applications where purity is crucial.
Glass-filled PEEK (GF30 PEEK): As the name suggests, this type incorporates 30% glass fibers, enhancing its mechanical properties. It provides increased stiffness and dimensional stability, making it suitable for structural components.
Carbon-filled PEEK (CF30 PEEK): With 30% carbon fiber reinforcement, CF30 PEEK takes strength and rigidity to the next level. It's the go-to choice for applications that demand the highest performance.
PVX Black PEEK: This specialized grade combines the benefits of PEEK with the added advantage of low friction and improved wear resistance. It's perfect for moving parts and dynamic applications.
Beyond these standard types, manufacturers can also customize PEEK to meet specific requirements. From static dissipative properties to metal and x-ray detectability, the possibilities are endless.
Properties of PEEK
When it comes to high-performance plastics, PEEK stands out from the crowd. Its unique combination of properties makes it a true engineering marvel. Let's take a closer look at what makes PEEK so special.
Mechanical Properties
PEEK is known for its exceptional mechanical strength. It can handle the toughest loads without breaking a sweat.
Tensile Strength: PEEK boasts an impressive tensile strength of up to 100 MPa. That's stronger than many metals!
Flexural Modulus: With a flexural modulus ranging from 3.8 to 4.3 GPa, PEEK offers outstanding stiffness. It maintains its shape even under extreme stress.
Hardness: PEEK's hardness is rated at 85-95 on the Rockwell M scale. It resists wear and tear like a champ.
Thermal Properties
One of PEEK's most remarkable features is its ability to withstand extreme temperatures. Here's a quick overview of its thermal properties:
Melting Point: PEEK has a melting point of 343°C (649°F). That's hot enough to handle most industrial applications.
Glass Transition Temperature: The glass transition temperature of PEEK is around 143°C (289°F). It maintains its mechanical properties even at elevated temperatures.
| PEEK 450 G Unfilled | PEEK 90GL30 GF30% | PEEK 450CA30**CF30%** | PEEK 150G903**Black** |
|
| Physical | Density (g/cm3) | 1.30 | 1.52 | 1.40 | 1.30 |
| Shrinkage Rate (%) | 1 to 1.3 | 0.3 to 0.9 | 0.1 to 0.5 | 1 to 1.3 |
|
| Shore Hardness (D) | 84.5 | 87 | 87.5 | 84.5 |
|
| Mechanical | 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 |
|
| Injection Molding | 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 |
|
Chemical Resistance
PEEK is a tough cookie when it comes to chemical resistance. It can handle exposure to a wide range of harsh substances:
Resistance to Acids, Bases, and Solvents: PEEK is resistant to most acids, bases, and organic solvents. It can withstand prolonged exposure without degrading.
Limitations in Chemical Resistance: However, PEEK does have some limitations. It can be affected by concentrated sulfuric acid and some halogenated hydrocarbons.
Other Notable Properties
PEEK has a few more tricks up its sleeve. Here are some other properties that make it stand out:
Biocompatibility: PEEK is biocompatible, making it suitable for medical implants and devices. It won't harm living tissue.
Wear Resistance: With its high hardness and low friction, PEEK offers excellent wear resistance. It's perfect for moving parts and dynamic applications.
Low Flammability: PEEK has a low flammability rating (UL94 V-0). It won't easily catch fire or contribute to the spread of flames.
Electrical Insulation: PEEK is an excellent electrical insulator. It maintains its insulating properties even at high temperatures.
How is PEEK Manufactured?
Have you ever wondered how PEEK, the superstar of high-performance plastics, is made? The process is as fascinating as the material itself. Let's dive into the world of PEEK manufacturing and discover how this incredible polymer is born.
Step-Growth Polymerization Process
PEEK is created through a process called step-growth polymerization. This is a chemical reaction where monomers, the building blocks of polymers, are joined together one step at a time.
In the case of PEEK, two main monomers are used:
These monomers are mixed together in the presence of a catalyst, usually sodium carbonate (Na2CO3). The reaction takes place at high temperatures, typically around 300°C (572°F).
Reaction of Monomers to Form PEEK Polymer
The magic happens when the monomers start to react with each other. The fluorine atoms on the DFB monomer are displaced by the hydroxyl groups on the HQ monomer. This creates a new carbon-oxygen bond, forming the backbone of the PEEK polymer chain.
As the reaction progresses, more and more monomers are joined together, growing the polymer chain step by step. This process continues until most of the monomers have been consumed, resulting in a long, repeating chain of PEEK polymer.
Isolation of PEEK Polymer
Once the polymerization reaction is complete, the newly formed PEEK polymer needs to be isolated from the reaction mixture. This is typically done through a series of washing and filtration steps.
First, the reaction mixture is cooled down to room temperature. It is then washed with water to remove any unreacted monomers and the sodium carbonate catalyst.
Next, the PEEK polymer is filtered to remove any remaining impurities. It is then dried to remove any residual moisture.
Finally, the PEEK polymer is ready to be processed into the various forms needed for injection molding, such as pellets or granules.
The beauty of this process is its simplicity. By carefully controlling the reaction conditions and the purity of the monomers, manufacturers can produce PEEK with incredibly consistent properties, making it a reliable choice for high-performance applications.
Advantages and Disadvantages of PEEK Plastic
Advantages
High Chemical Resistance: PEEK can withstand exposure to a wide range of chemicals, even at elevated temperatures. This makes it ideal for use in harsh environments where other materials would quickly degrade.
Excellent Strength, Hardness, and Stiffness: PEEK boasts impressive mechanical properties. It has a high strength-to-weight ratio, making it a lightweight yet sturdy choice for structural components. Its hardness and stiffness allow it to maintain its shape under heavy loads.
Resistance to High-Pressure Water and Steam: PEEK's resistance to hydrolysis is remarkable. It can withstand exposure to high-pressure water and steam without losing its properties. This makes it a top choice for applications in the oil and gas industry.
Suitability for Medical and Dental Applications: PEEK's biocompatibility and resistance to sterilization processes make it an excellent choice for medical and dental applications. From surgical instruments to implants, PEEK is helping to improve patient outcomes.
High Creep Resistance: PEEK has excellent creep resistance, meaning it can maintain its shape under constant load over long periods. This is crucial for applications where dimensional stability is critical, such as in aerospace components.
Low Smoke and Toxic Gas Emission: In the event of a fire, PEEK emits minimal smoke and toxic gases. This is a crucial safety consideration for applications in the transportation and building industries.
Inherent Flame Retardancy: PEEK has a natural resistance to flames, making it a safer choice than many other plastics. It can withstand temperatures up to 300°C (572°F) without igniting.
Durability and Wear Resistance: PEEK's high strength and hardness make it resistant to wear and tear. This durability makes it a cost-effective choice for applications where parts need to last for a long time.
Disadvantages
High Cost Compared to Other Resins: PEEK is a premium material, and its price reflects that. It is more expensive than many other engineering plastics, which can be a barrier to its adoption in some applications.
Low Resistance to UV Light: PEEK has poor resistance to ultraviolet (UV) light. Prolonged exposure to sunlight can cause it to degrade and lose its properties. This can be a problem for outdoor applications.
High Processing Temperatures: PEEK's high melting point means that it requires high processing temperatures. This can be a challenge for some injection molding machines and can increase energy costs.
Rudimentary Cell Adhesion for Medical Applications: While PEEK is biocompatible, its surface doesn't naturally promote cell adhesion. This can be a problem for some medical applications where tissue integration is desired. However, surface treatments can be applied to improve cell adhesion.
Despite these drawbacks, the advantages of PEEK often outweigh the disadvantages for many applications. Its unique combination of properties makes it a material that is hard to beat.
PEEK Injection Molding Process
Injecting molding PEEK is a delicate dance that requires precision and expertise. From pre-molding preparations to design considerations, every step plays a crucial role in the final product. Let's dive into the nitty-gritty of the PEEK injection molding process.
Pre-Molding Preparations
Before we even think about injecting molding PEEK, we need to get our ducks in a row. Proper preparation is key to success.
Drying Temperature and Time: PEEK is a hygroscopic material, which means it absorbs moisture from the air. To avoid defects, it needs to be dried before molding. The recommended drying temperature is 150°C (302°F) for 3-4 hours.
Material Preparation and Handling: PEEK pellets should be stored in a cool, dry place. They should be kept in sealed containers to prevent moisture absorption. When handling PEEK, it's important to wear gloves to avoid contamination.
Molding Parameters
Once we've got our material ready, it's time to dial in the molding parameters. These settings can make or break the final product.
Injection Pressure and Speed: PEEK requires high injection pressures, typically between 70-140 MPa (10,000-20,000 psi). The injection speed should be fast enough to fill the mold quickly, but not so fast that it causes defects.
Temperature Control: The melt temperature for PEEK is typically between 360-400°C (680-752°F). The mold temperature should be kept between 170-200°C (338-392°F) to ensure proper crystallization and minimize warping.
Shrinkage Rates and Control: PEEK has a shrinkage rate of 1-2%, depending on the grade and fillers. To control shrinkage, it's important to maintain consistent mold temperatures and packing pressures.
Check out this table for a quick reference on PEEK molding parameters:
| Parameter | Value |
| Drying Temperature | 150°C (302°F) |
| Drying Time | 3-4 hours |
| Melt Temperature | 360-400°C (680-752°F) |
| Mold Temperature | 170-200°C (338-392°F) |
| Injection Pressure | 70-140 MPa (10,000-20,000 psi) |
| Shrinkage Rate | 1-2% |
Design Considerations
Designing parts for PEEK injection molding requires a bit of know-how. Here are some key considerations to keep in mind:
Wall Thickness: PEEK can be molded into thin-walled parts, but it's important to maintain a consistent wall thickness. The recommended range is 1.5-4 mm (0.06-0.16 in).
Radii and Sharp Edges: Sharp edges and corners should be avoided in PEEK parts. They can cause stress concentrations and make the part more difficult to mold. A minimum radius of 0.5 mm (0.02 in) is recommended.
Draft Angles: Draft angles are necessary for easy ejection of the part from the mold. A minimum draft angle of 1° is recommended for PEEK parts.
Part Tolerances: PEEK can be molded to tight tolerances, but it's important to consider the shrinkage rate and the limitations of the molding process. A tolerance of ±0.1 mm (±0.004 in) is typically achievable.
Applications of PEEK Injection Molded Parts
Automotive Industry
The automotive industry is always looking for ways to improve fuel efficiency and reduce emissions. PEEK injection molding offers a solution.
Replacement of Metal Parts with PEEK Components: PEEK's high strength-to-weight ratio allows it to replace heavy metal parts, reducing overall vehicle weight and improving fuel economy. Its ability to withstand high temperatures and chemicals makes it ideal for under-the-hood applications.
Examples of PEEK Automotive Parts: PEEK is used in a variety of automotive components, such as gears, bearings, and valve seats. It's also found in fuel system parts, where its chemical resistance and high-temperature stability are crucial.
Medical and Dental Applications
PEEK's biocompatibility and chemical resistance make it a top choice for medical and dental applications.
PEEK's Inertness and Resistance to Chemicals: PEEK is inert and resistant to most chemicals, making it safe for use in the human body. It can withstand the harsh sterilization processes required for medical devices.
Biomedical and Dental Use Cases: PEEK is used in a range of biomedical applications, from spinal implants to dental prostheses. Its bone-like mechanical properties and ability to integrate with human tissue make it an ideal choice for these applications.
Electrical Applications
PEEK's unique electrical properties make it a valuable material for the electrical industry.
PEEK as an Electrical Insulator: PEEK has excellent electrical insulation properties, making it suitable for use in high-voltage applications. Its ability to maintain these properties at high temperatures sets it apart from other plastics.
High-Temperature Electrical Components: PEEK's high-temperature stability allows it to be used in electrical components that are exposed to extreme heat, such as connectors and switches in aerospace and automotive applications.
Food Industry Applications
PEEK's purity and chemical resistance make it safe for use in the food industry.
FDA Approval for Food Contact: PEEK meets FDA requirements for food contact, making it suitable for use in food processing equipment and packaging.
PEEK in Food Packaging and Oven Parts: PEEK's high-temperature stability and chemical resistance make it ideal for use in food packaging and oven components, where it can withstand the harsh conditions of cooking and sterilization.
Aerospace Industry
PEEK's lightweight nature and high-performance properties make it a valuable material for the aerospace industry.
PEEK as a Lightweight Alternative to Aluminum: PEEK's high strength-to-weight ratio allows it to replace aluminum in aircraft components, reducing overall weight and improving fuel efficiency.
PEEK Components in Aircraft: PEEK is used in a variety of aircraft components, from structural parts to electrical connectors. Its ability to withstand extreme temperatures and chemicals makes it ideal for the harsh conditions of aerospace applications.
Check out this table comparing the properties of PEEK and aluminum:
| Property | PEEK | Aluminum |
| Density (g/cm³) | 1.32 | 2.70 |
| Tensile Strength (MPa) | 90-100 | 70-700 |
| Continuous Use Temperature (°C) | 260 | 150-250 |
| Chemical Resistance | Excellent | Good |
Final Thought
PEEK injection molding offers many advantages, including exceptional strength, heat resistance, and chemical inertness. It is widely used in medical, aerospace, and automotive industries. Choosing the right PEEK grade is crucial for achieving optimal performance in specific applications. With ongoing advancements, the future of PEEK looks promising across various sectors. Its versatility and durability will continue to drive innovation and adoption.
Team Mfg: Your Trusted Partner for PEEK Injection Molding
With decades of experience and a commitment to quality, Team Mfg delivers PEEK injection molding solutions for your most demanding applications. Contact us today to discuss your project requirements and learn how we can help you succeed.
