Friction and wear are two significant factors affecting the lifespan and performance of plastic components in dynamic applications. This article explores the fundamental properties of polymers and highlights key material types that are commonly used for applications where low friction and high wear resistance are critical. Keep an eye out for our follow-up article, where we’ll take a dive into how specific additives and fillers can dramatically boost the wear resistance and friction reduction of these polymers.
Wear and Friction in Plastics
Friction is the force that opposes motion between two surfaces in contact. In plastics, friction can generate heat, leading to dimensional changes or even melting. Wear, on the other hand, is the gradual removal of material from a solid surface due to mechanical action. Both are critical factors that directly impact a plastic component’s lifespan and overall performance.
Wear and Friction Considerations in Material Selection
Wear and Friction Considerations in Material SelectionChoosing the ideal plastic material is crucial for an application’s success. An unsuitable choice can cause a part to fail prematurely, leading to lost energy from friction and higher costs due to frequent replacement and maintenance. The right material selection is essential for maximizing a component’s durability and cost-effectiveness.
The tribological performance of a polymer is fundamentally dictated by its intrinsic properties. Hardness provides resistance to abrasive wear by preventing sharp, harder particles from cutting or plowing into the polymer’s surface. The thermal conductivity of a plastic is an important consideration as a material with higher thermal conductivity allows it to efficiently dissipate the heat generated by friction, preventing a localized temperature increase that can soften or degrade the polymer. In addition, chemical resistance is vital for ensuring the polymer maintains its integrity when exposed to different operating fluids or environments. A polymer’s thermal resistance — its melting and glass-transition temperatures — determines its ability to withstand frictional heat without undergoing a phase change. Lastly, the surface roughness of both the polymer and its mating surface directly impacts friction and wear; a smoother surface generally leads to lower friction and less wear; however, some roughness may be needed to hold a lubricant film in place if applicable.
While a plastic’s intrinsic properties are important, its performance in a real-world application is also heavily influenced by the operating conditions. A critical design consideration is the pressure-velocity (PV) limit, which represents the maximum combination of contact pressure (P) and sliding velocity (V) that a polymer can withstand without generating excessive heat and failing prematurely. Factors like temperature, the mating surface’s characteristics (e.g., roughness, material type), and lubrication each play a significant role. Therefore, a successful design requires a comprehensive approach that considers both the material’s properties and the specific demands of the application.
Common Resins Used in Wear and Friction Applications
When selecting materials for your application, you don’t need to reinvent the wheel. There are multiple thermoplastic resins that have been historically used in wear applications with success.
Nylon/polyamide (PA)
PA resins are typically regarded as the most common general-purpose, wear-resistant plastic with PA 66 and PA 6 being the most used polymers from this family. PA resins have high stiffness, strength and hardness. In dry applications, they typically outwear polyoxyethylene (POM) or acetal resins 4:1. They are considered abrasion resistant and possess a relatively low coefficient of friction. The downfall of PA resins is their high moisture sensitivity. They readily absorb moisture, which acts as a plasticizer for the material, decreasing its hardness and stiffness. One option within this family for high-moisture and high-temperature environments is the use of semi-aromatic polyamides, such as polyphthalamide (PPA). These offer much lower moisture absorption and show excellent property retention at high temperatures.
Polyoxymethylene/acetal (POM)
POM is another commonly used wear-resistant thermoplastic resin. Unfilled grades feature a low coefficient of friction as well as a minimal difference between static and dynamic coefficients of friction, making them ideal for applications requiring low startup torque or moments. POM also demonstrates high stiffness and hardness as well as good chemical and thermal resistance. In wear applications, POM is well suited for sliding applications with medium to high loads such as bearings and gears. However, it offers less resistance to abrasive wear than other common thermoplastics used in wear applications.
Ultra-high molecular weight polyethylene (UHMW-PE)
UHMW-PE is an extremely tough material coupled with a very low coefficient of friction that is similar to polytetrafluoroethylene (PTFE). It is softer than other polymers in the application but offers much higher impact strength than other materials. It has excellent abrasion resistance — the highest of any unfilled resin mentioned in this article. Furthermore, it has good chemical resistance and a very low glass-transition temperature (Tg) below -100°C (-148°F). This makes it well suited for subambient wear applications in the coldest environments.
Polytetrafluoroethylene (PTFE)
PTFE offers the lowest coefficient of friction for any plastic listed in this article. It also has great chemical resistance and a very high melting point at about 325°C (617°F) making it suitable for use in high-temperature applications. In straight wear applications, it has a very high wear factor (K) and wear rate, thus making it a poor choice for traditional wear applications. PTFE shines as an additive within other plastic materials to lower their coefficient of friction. In some applications, the wear factor can be lowered by almost four times with the addition of 20% PTFE.
Aliphatic polyketone (POK/PK/APK)
POK is a terpolymer of ethylene, carbon monoxide and a small amount of propylene. It has similar tensile strength to POM but has reduced stiffness — the tensile modulus of POK is half of POM. This is made up for by an increased elongation at break and better impact strength. POK exhibits a hard surface and typically shows less wear and surface degradation over time as compared to POM. In some studies, wear rates for pin-on-disc abrasion wear testing showed that POK had a wear rate over four times lower than POM. POK could work well in similar POM applications that need increased wear resistance and toughness. One other benefit of POK is very low moisture absorption. This makes it better suited for some high-moisture environments where nylon resins may struggle with property changes, and it is more hydrolysis resistant than polyester resins like polybutylene terephthalate (PBT), polyethylene terephthalate (PET), etc.
Polyphenylene sulfide (PPS)
PPS is a semi-crystalline resin that is typically compounded with glass-fiber reinforcement, as well as mineral filler content. PPS itself has good thermal properties, good chemical resistance and inherent flame resistance. With the addition of glass fibers, PPS gains high strength and stiffness, good dimensional stability, improved impact resistance and good electrical insulative properties. For these reasons, PPS is a good replacement material for metal and thermoset parts, and it can provide a similar look and feel to metal components. In straight wear applications, it can show similar wear rates to PA resins and is an excellent choice for wear in high-temperature and chemically aggressive environments.
Polyether ether ketone (PEEK)
PEEK is a material that contains nearly the highest Tg (145°C) and melting point (335°C) — 293°F and 635°F, respectively — for semi-crystalline thermoplastic. It also boasts high mechanical properties, including good impact strength and chemical resistance. It has a similar coefficient of friction to PA 66, and in straight wear applications, it performs better than neat PTFE and acetal but worse than the other materials in this article. Due to these factors as well as cost, PEEK typically finds use in wear applications in extremely high temperatures where PPS cannot be used.
To aid in material selection, Table 1 provides a comparison of wear- and friction-related properties for the materials discussed in this analysis. Crucially, these values represent unfilled grades — except for 30% glass-reinforced PPS. For properties of specific grades, consulting the technical datasheet and conducting physical wear testing under application conditions are always recommended.
Table 1. A comparison of wear- and friction-related properties for materials discussed in this analysis. Source: The Madison Group. 1 Friction and Wear of Polymers – Zeus Industrial Products Inc., pages 5-8. 2 Ünal, Hüseyin & Sen, Ugur & Mimaroglu, A. (2005). Abrasive wear behavior of polymeric materials. Materials & Design. 26. 705-710. 10.1016/j.matdes.2004.09.004.
Wear and Friction – A Holistic View
In conclusion, material selection for wear and friction applications should take a holistic view of all critical requirements for the applications, including mechanical properties, temperature, chemical resistance, environmental resistance, etc. Material comparisons and datasheets are good starting points for the selection process. However, wear and friction are highly dependent on the specific conditions present: the two materials contacting each other, lubrication, temperature, contact pressure, sliding velocity, etc. To ensure material performance, it’s essential to validate potential candidates by running physical wear tests that replicate the application conditions. This will confirm what material is best suited for your wear and friction application over the entire lifetime of the part.
Only neat polymers, except for glass-reinforced PPS, were discussed in this article. Many commercially available wear-resistant resin grades also incorporate additives and fillers. We will dedicate a subsequent article to discussing these, explaining how they dramatically enhance the wear and friction characteristics of base polymers.
This article was originally published in the January 2026 edition of Plastics Technology.
