Although both PTFE and PEEK are well established within their respective fields, there are frequently questions around which would better suit a given application. OEMs typically have to make a choice based on technical suitability and hence need to be better informed as to how these materials match up against each other. The PEEK vs PTFE decision usually comes down to balancing mechanical strength against chemical and electrical performance.
Below is a short comparison of properties between these two polymers and can be used as a guide to aid new product development.
Parameter | PTFE | PEEK | Preferred material |
Price | Moderately expensive | Very expensive | PTFE |
Tensile Strength | 25-35 MPa | 90-100 MPa | PEEK |
Elongation | 350-400% | 30-40% | PTFE |
Compressive Strength | 30-40 MPa | 140 MPa | PEEK |
Flexural Modulus | 495 MPa | 3900 MPa | PEEK |
Coefficient of Friction | 0.03-0.05 | 0.35-0.45 | PTFE |
Temperature resistance | Up to 250°C | Up to 250°C | NA |
Dielectric strength | 50-150 kV/mm | 50 kV/mm | PTFE |
Chemical resistance | Virtually inert | Affected by Sulphuric acid | PTFE |
Coefficient of linear thermal expansion | 14 x 10⁻⁵/K | 5 x 10⁻⁵/K | PEEK |
Machine-ability | Good | Very good | PEEK |
A few of these figures deserve a closer look. The PEEK coefficient of thermal expansion is roughly a third that of PTFE, which is why PEEK holds tighter dimensional tolerances over a temperature swing. The PEEK friction coefficient of 0.35–0.45 is considerably higher than PTFE's, so where low friction is the priority, PTFE has the clear edge.
It is also worth noting the thermal limits beyond the shared 250°C working figure. The PTFE temperature rating reflects continuous-use service up to around 250–260°C, while PEEK's headroom is defined by its thermal transitions: the PEEK glass transition temperature sits at approximately 143°C, and the PEEK melting point is around 343°C, which allows it to retain mechanical strength at elevated temperatures where PTFE has already softened.
On corrosion, the PEEK vs PTFE chemical resistance comparison favours PTFE, which is virtually inert, whereas PEEK can be attacked by concentrated sulphuric acid.
In a nutshell, applications requiring strength and low levels of deformation would usually employ PEEK, whereas those requiring resistance to voltage or chemicals utilise PTFE. PTFE also rates highly in that it is self-lubricating. This makes it a preferred choice in high-wear applications.
The biggest disadvantage of PEEK remains the price. It is roughly 10 times the price of PTFE and, as a result, has remained a niche polymer, used only in applications where it is absolutely necessary.
