Tuesday, November 19, 2013

PTFE vs PEEK – A Comparison of Properties

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.
Below is a short comparison on properties between these two polymers and can be used a guide to aid new product development.
ParameterPTFEPEEKPreferred material
PriceModerately expensiveVery expensivePTFE
Tensile Strength25-35 Mpa90-100 MpaPEEK
Compressive Strength30-40 Mpa140 MpaPEEK
Flexural Modulus495 Mpa3900 MpaPEEK
Coefficient of Friction0.03-0.050.35-0.45PTFE
Temperature resistanceUp to 250°CUp to 250°CNA
Dielectric strength50-150 Kv/mm50 Kv/mmPTFE
Chemical resistanceVirtually inertAffected by Sulphuric acidPTFE
Coefficient of linear thermal expansion14 x 10-5/K5 x 10-5/KPEEK
Machine-abilityGoodVery goodPEEK
In a nutshell, applications requiring strength and low levels of deformation would usually employ PEEK, whereas those requiring resistance to voltage or chemicals utilize 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.