What is PEEK?

PEEK (Polyetheretherketone) is a high-performance engineering thermoplastic that belongs to the family of polyaryletherketones. PEEK material is known for its exceptional mechanical, thermal, and chemical properties, which make it suitable for a wide range of applications in various industries. This guide is designed to give you a deeper understanding of the material PEEK. We’ll look at the properties of PEEK plastic, covering:
 
Advantages and disadvantages of PEEK plastic
PEEK plastic applications in different industries
How PEEK plastic is manufactured
Considerations when designing for PEEK plastic
Future developments and trends in PEEK plastic technology

Advantages and disadvantages of PEEK plastic

Peek characteristics derive from polyetheretherketone properties. Its durability and broad temperature range – especially its resistance to high temperatures – make it an effective solution for manufacturers. Demand for this material is increasing among manufacturers as the need increases for higher mechanical properties at lighter weight. PEEK polymer can actually be used as an alternative to metal in many instances. Here’s a look at the PEEK properties that make it a versatile material across a range of applications. We’ll also look at the material’s disadvantages.

Advantages

●      Excellent high-temperature resistance:
PEEK products can generally withstand temperatures up to 180°C continuous use, ensuring a long life and reliability in harsh environments. PEEK temperature range varies, depending on the grade. Some grades can be used continuously at temperatures up to 250°C. Note, PEEK material temperature range starts at -70°C. PEEK material melting temperature is generally 343°C.
 
●      Mechanical strength and high dimensional stability:
PEEK plastic material exhibits excellent properties in terms of strength, stiffness, creep and fatigue, enabling the manufacture of lightweight parts, and better performance over time. Wear resistance in abrasive or humid environments, a low coefficient of friction and excellent wear resistance can help prolong the life and maintain the integrity of the parts.
 
●      Lightweight:
PEEK material properties translate to light weight. It has a low density, typically about 1/5 to 1/6 of the weight of metal, which is why it’s often the preferred material.
 
●      Chemical resistance:
A PEEK component has outstanding chemical resistance, even at high temperatures, thanks to the material’s ability to withstand many acids, bases, hydrocarbons and organic solvents.
 
●      Electrical performance:
Is PEEK electrically conductive? No. PEEK electrical properties are excellent over a wide range of temperatures and frequencies. With exceptional insulation characteristics, PEEK is outstanding for  electrical engineering and electronics – especially when you factor in PEEK heat resistance.
 
●      Thermal insulation:
The thermal properties of PEEK give it a low coefficient of thermal conductivity. Hence, PEEK offers excellent insulation. PEEK mechanical properties and high-temperature resistance make it an ideal choice for thermal stability.
 
●      Hydrolysis resistance:
PEEK products have been used successfully to improve the reliability of components. With low moisture absorption, PEEK does not hydrolyse in the presence of water (freshwater, salt water or steam), even at high temperatures.
 
●      Recyclable:
The properties of Peek make it completely recyclable and halogen-free. The polymer PEEK also complies with the European RoHS directive and REACH.

Disadvantages

●      Cost:
PEEK material price is relatively expensive compared to many other thermoplastics. The cost of PEEK can be a limiting factor, especially for applications that require large volumes or where cost-effectiveness is a primary consideration.
 
●      Processing Challenges:
PEEK plastic melting point is typically around 343°C, which can make it challenging to process. Specialised equipment and processing techniques, such as injection moulding machines capable of high-temperature operation, are often required. PEEK plastic in injection moulding is common, but this can add complexity and cost to manufacturing processes.
 
●      Limited Availability:
Compared to more common thermoplastics like polypropylene or polyethylene, PEEK may have limited availability in certain regions or markets. This can result in longer lead times or higher costs for sourcing PEEK components or materials – always check availability early with your PEEK material supplier.
 
●      Low resistance to UV:
Plastic PEEK is generally susceptible to degradation when exposed to prolonged UV radiation, particularly in outdoor or high-exposure environments. However, additives such as UV stabilisers can mitigate degradation for PEEK polymer uses.
 
●      Limited Color Options:
PEEK is typically available in natural (light brown) or black colour variations. Compared to some other polymers, it offers a limited range of colour options. This may be a consideration for applications where colour coding or aesthetics are important.
 

PEEK plastic applications in different industries

PEEK polymer applications are found in various components suited for a range of industries. The components shown here withstand higher temperatures and forces than their standard Nylon counterpart, making them better suited for heavy-duty environment applications. All are rated UL94 V-0.
 

PEEK polymer properties and their advantages make these and other components useful to the following industries. PEEK plastic uses include:
 
1.    Aerospace:
Structural parts, brackets, electrical connectors, cable insulation, and fuel system
components.
 
2.    Automotive:
Engine components, electrical connectors, fuel system parts, piston parts, and bearings.
 
3.    Oil and Gas:
Downhole equipment, pump components, valves, seals, and electrical connectors.
 
4.    Electrical and Electronics:
Insulation materials, connectors, sockets, circuit boards, cable insulation, and high-temperature wire coatings.
 
5.    Medical and Dental:
PEEK is biocompatible. For this reason, PEEK implant material and PEEK dental material are common. It’s also used in surgical instruments and orthopaedic devices.
 
6.    Chemical Processing:
Pumps, valves, seals, gaskets, and connectors.
 
7.    Food Processing:
Conveyor belts, gears, bearings, and seals. Also suitable for repeated food contact.

How PEEK plastic is manufactured

PEEK manufacturers use a process called polymerisation. The production of PEEK involves several steps:
1.    Monomer Synthesis: The first step involves the synthesis of the monomers used to produce PEEK. The monomers used are para-difluorobenzene (p-DFB) and 4,4'-difluorobenzophenone (DFBP). These monomers are synthesised through various chemical reactions and purification processes.
2.    Polymerisation: The monomers are subjected to high-temperature polymerisation. This is typically carried out using a process called step-growth polymerisation or condensation polymerisation. In this process, the monomers are reacted together under controlled conditions, such as high temperature and vacuum, to form polymer chains.
3.    Post-Processing: After polymerisation, the PEEK resin is usually in the form of granules or pellets. These resin pellets can undergo further processing steps to enhance their properties or transform them into different forms as required for specific applications. The post-processing steps can include:
●      PEEK plastic extrusion: The pellets are melted and forced through a die to form continuous profiles, rods, sheets, or films.
●      PEEK plastic injection moulding: The molten PEEK resin is injected into a mould cavity under high pressure, where it cools and solidifies, taking the shape of the mould. Learn more in  The Definitive Guide to Plastic Injection Moulding.
●      PEEK plastic machining: Machining PEEK plastic can be done using conventional methods such as cutting, drilling, or milling to achieve the desired shape and dimensions.
4.    Additional Treatments: Additional treatments may include annealing (heat treatment to relieve internal stresses), surface coatings, or other post-processing steps to enhance specific properties, such as UV resistance.

Considerations when designing for PEEK plastic

You’ll need to consider several factors to ensure optimal performance and functionality of the final product. Understand the specific PEEK physical properties and how those properties align with your application’s requirements.
 
Take into account the mechanical loads and stresses the PEEK component will experience during use. Consider factors such as part geometry, wall thickness, ribbing, fillets, and other design features to optimise strength, stiffness, and load-bearing capabilities. Avoid sharp corners or abrupt changes in sections to minimise stress concentration.
 
PEEK has exceptional thermal stability, but it can still be affected by excessively high temperatures. PEEK plastic temperature range is wide. But you’ll still need to consider the operating temperature range of your application and design the component to withstand the anticipated thermal conditions. Allow for thermal expansion and contraction, and consider the need for additional cooling or insulation measures if required.
 
Keep in mind, too, that PEEK exhibits broad chemical resistance, including harsh solvents, acids, and bases. However, certain chemicals – specifically, nitric acid and sulphuric acids – can still impact PEEK over extended exposure or at elevated temperatures. You should consider PEEK material compatibility. Evaluate the chemical environment the component will be exposed to and ensure it’s compatible with PEEK's chemical resistance.
 
Finally, while it’s a tough and wear-resistant material, machining peek plastic material has its challenges. Consider the appropriate tooling, cutting speeds, and feeds to achieve the desired precision and surface finish for your PEEK polymer applications. Work closely with experienced manufacturers or machinists familiar with PEEK to optimise the manufacturing process.

Future developments and trends in PEEK plastic technology

While advancements in PEEK engineering plastic have already positioned it as a high-performance material, ongoing research and development are expected to bring further improvements. Some potential future developments and trends in PEEK plastic technology include
improving processing techniques. This will include additive manufacturing methods specifically designed for PEEK to make fabrication more efficient and accessible.
 
Enhanced Reinforcement is another area ripe for development: PEEK composites with reinforced materials such as carbon fibres or nanoparticles will improve mechanical properties such as strength, stiffness, and fatigue resistance. These advancements will expand the range of applications for PEEK in industries where exceptional performance is required.
 
Research is also focused on developing surface modifications for PEEK physical properties to enhance its functionality. This includes creating bioactive surfaces to improve osseointegration in medical implants or introducing coatings that provide antimicrobial properties for applications in healthcare settings.
 
Advanced testing and simulation is another area of interest. As computational tools and simulation techniques advance, researchers will have better capabilities to model and predict PEEK's behaviour under different conditions. This will aid in optimising designs, reducing the need for extensive prototyping, and accelerating the development process.
 

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