PTFE vs. PEEKJohn Moot
High-performance plastics are characterized primarily by their temperature resistance, but also by their mechanical properties.
They are often chosen for applications that require good chemical resistance, performance at high temperatures, low coefficient of friction and high strength.
They are found in many demanding applications in a variety of industries including oil and gas, aerospace, nuclear and chemical, but how do you decide which material has the properties needed for your specific application?
Although both PTFE and PEEK are well established in their respective fields, the question often arises as to which material is better suited for a particular application. OEMs typically need to make a selection based on technical suitability and therefore need to be better informed on how these materials compare.
What’s in PTFE’s favor?
PTFE is a versatile and cost-effective material with medium tensile strength. It has very good thermal properties and excellent chemical inertness, especially to strong acids. The coefficient of friction is unusually low and is said to be lower than any other solid material. PTFE is an excellent electrical insulator over a wide range of temperatures and frequencies.
PTFE is a thermoplastic. However, due to its high viscosity, PTFE cannot be processed using conventional polymer processing techniques. Therefore, PTFE is processed by cold forming followed by heat treatment (sintering), which fuses the polymer particles into a solid molded part.
PTFE films are peeled from such blocks.
Applications of PTFE:
- Pharmaceutical and medical technology
- Chemical industry
Delivery forms of PTFE:
Sheets, tubes, rods, films, finished parts.
Properties of PTFE:
- High chemical resistance
- Minimal surface tension
- Difficult to bond or weld
What are the advantages of PEEK?
PEEK is a semi-crystalline thermoplastic with excellent mechanical and chemical resistance properties that are maintained even at high temperatures. It is highly resistant to thermal degradation and to attack by organic and aqueous environments.
PEEK is attacked by halogens and strong acids, as well as by some halogenated compounds and aliphatic hydrocarbons at high temperatures. It dissolves completely in concentrated sulfuric acid at room temperature.
PEEK can be processed by conventional methods such as injection molding, extrusion and compression molding. PEEK is a much more expensive polymer, but adds value by allowing parts to be made with properties such as light weight, strength or toughness, and the ability to survive longer in harsh environments.
Applications for PEEK:
- Food industry
- Medical technology
Delivery forms of PEEK:
Sheets, tubes, rods, foils, finished parts
Properties of PEEK:
- High chemical resistance
- Excellent sliding function
- Very high temperature resistance
PEEK vs. PTFE
PEEK and PTFE are compared in 4 areas:
- Tensile strength
- Temperature resistance
- Wear resistance
- chemical resistance
PEEK vs. PTFE: High tensile strength
In the polymer field, it’s hard to find anything tougher than PEEK. In fact, it’s so strong that PEEK is subject to the same machining guidelines as metals.
This strength allows PEEK to be used in applications such as seals and automotive components – especially where metals cannot be used but metal-like resistance is required.
PEEK vs. PTFE: High temperature resistance
PEEK melts at about 400 degrees Fahrenheit and is capable of operating in environments of 300-325 degrees without deforming. While PTFE can withstand up to 250 degrees, any pressure/stress on PTFE at this temperature will inevitably cause deformation. In the case of PEEK, its hardness allows it to be used in a high-stress, high-temperature environment without losing its molding properties.
PEEK vs. PTFE: High wear resistance
Again, while both PTFE and UHMWPE can withstand significant wear, PEEK has a high PV value and can withstand wear in harsh physical and chemical conditions.
PEEK vs. PTFE: Chemical Resistance.
While PEEK is not on the same level as PTFE in terms of pure chemical inertness, it does exhibit resistance to many aggressive chemicals, allowing it to be used in corrosive environments and under heavy loads.
In short, PEEK’s ability to remain dimensionally stable under harsh conditions makes it a highly sought-after polymer. OEMs that use PEEK do so knowing full well that PEEK is unique for the properties it offers and therefore expensive.
In summary, PEEK has remained a niche polymer primarily because of its high price. If it were cheaper – at about the price of PTFE – it could capture a significant portion of the PTFE market. PTFE is still much better than PEEK in properties such as coefficient of friction and dielectric strength, but when it comes to pure strength, PEEK is unsurpassed among polymers.