Spring Energized PTFE Seal
by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Unlocking Performance with PPS: High-Strength Polymer Solutions for Extreme Environments

PPS (polyphenylene sulfide) is a high-performance, semi-crystalline engineering polymer widely used in industries such as aerospace, automotive, electronics, and industry. It combines mechanical strength with chemical resistance and excellent thermal and dimensional stability. It has found extensive applications in replacing metals and other polymers when the performance requirements are particularly severe.

This blog post examines the molecular and structural foundations of PPS performance, its key engineering benefits, and its role in advanced applications that require reliability in harsh conditions.

PPS Fundamentals: Structure, Chemistry, and Material Properties

PPS consists of repeating para-phenylene groups linked by sulfide bridges. The backbone of this polymer is composed of benzene rings (rigid, strong) and sulfur atoms (flexible connectors, chemically resistant) that form it. The repeating pattern leads to high crystallinity (~65%), which increases strength, reduces creep, and improves wear resistance. This molecular structure is also where i gets its strength and excellent chemical resistance to problematic media such as solvents, fuels, and acids.

PPS also has a high melting point of ~285°C and can withstand continuous use temperatures of up to 220–240°C. Its glass transition temperature is typically around 90°C, and it is inherently flame-resistant, with UL 94 V-0 ratings achievable without additives.

In addition, PPS has a high modulus of elasticity, good tensile strength, excellent wear resistance, and a low moisture absorption rate of less than 0.05%. It is also electrically insulating with very stable dielectric properties.

Engineering Advantages of PPS in Harsh Environments

PPS also offers excellent advantages when used in harsh environments. As alluded to earlier, it possesses excellent chemical resistance to liquids such as strong acids, strong bases, alkalis, solvents, fuels, and hydraulic fluids. It is also resistant to automotive fluids, aerospace lubricants, steam and hot water, and most cleaning chemicals. It has proven to be an excellent choice for pump components, seals, and housings that are exposed to aggressive media.

Because of its high crystallinity and low creep, PPS is able to maintain tight tolerances, and its low coefficient of thermal expansion means it retains stability across a wide range of operating temperatures. Finally, it has been shown to outperform many other engineering plastics when it comes to precision components, including gears, valves, and compressor parts.

PPS blends with lubricants (e.g., PTFE, graphite, carbon fiber) to reduce friction and enhance wear resistance. This makes it quite effective in dry-running environments where lubricants may be impractical or impossible. Filled PPS is commonly used for automotive and industrial bearing surfaces.

PPS also exhibits consistent dielectric strength, which can be crucial for electronics and high-voltage systems. It also retains its insulating properties even after prolonged exposure to heat and chemicals. PPS is commonly used in connectors, sensors, and encapsulated electronic systems.

Applications of PPS in Advanced Systems

PPS is commonly used in many industries. For example, in the automotive and transportation industry, PPS is used in fuel system components (pumps, filters, connectors) due to hydrocarbon resistance. PPS is also found in EV and hybrid powertrain parts that demand thermal/electrical stability, and brake and clutch components where dimensional stability under load is critical.

In the aerospace and defense industries, PPS can be found in structural components, housings, and fasteners where metal replacement is advantageous. In addition, PPS composites (carbon fiber reinforced) offer high strength-to-weight ratios for aircraft interiors and UAVs. Also, flame resistance and low smoke/toxicity make PPS suitable for cabin environments.

In electronics, PPS is used in high-frequency connectors, coil bobbins, switch housings, and encapsulation materials, while PPS films and coatings provide insulation and chemical resistance in demanding circuit environments.

In industrial equipment, it is used in compressor rings, pump parts, seals, and valve seats, where PPS resists wear and chemical attack. PPS reinforced with carbon fiber or PTFE provides long-lasting service in bearings and sliding elements.

There are also some specialized applications of PPS, such as off-road and racing bikes using carbon-fiber-reinforced PPS for lightweight durability and chemical processing equipment resistant to acids, caustics, and solvents.

Conclusion

PPS is a go-to high-performance material that delivers where metals and conventional plastics fail. Its combination of thermal stability, chemical resistance, dimensional stability, and tribological performance has cemented its place in aerospace, automotive, electronics, and industrial sectors. And with continued advances in reinforcement technologies (e/g/, carbon fiber, lubricated fillers), PPS will expand into even more demanding applications, offering engineers a versatile material platform for the future.

If you are interested in PPS as a material for one of your designs, contact the experts at Advanced EMC.

by Sara McCaslin, PhD Sara McCaslin, PhD No Comments

Polymer Labyrinth Seals for Wind Turbine Gearboxes: Reducing Contamination and Extending Service Life

Wind turbine gearboxes operate in some of the harshest environments, from salty offshore platforms to dust-laden plains, and must run continuously for years with limited access to maintenance. At the heart of these systems lie high-speed rotating components, including the gearbox output shaft, the generator interface, and, in some direct-drive designs, high-speed rotor hubs.

This blog post examines polymer labyrinth seals as a solution for sealing the gearbox in powerful wind turbines.

Wind Turbine Gearboxes 

The gearbox is one of the most critical components in a wind turbine. It converts the relatively slow rotation of the blades into the high-speed rotational motion required by the generator. If the gearbox fails, the entire turbine is offline, leading invariably to lost power production and costly repairs. The fact that turbines are often installed in remote or offshore locations means that repair logistics can be difficult, expensive, and dangerous. 

The Challenge of Gearbox Contamination in Wind Turbines

Wind turbine gearboxes are highly susceptible to contamination and loss of lubricant through seal leaks. Sources of contamination are many, including dust, moisture, salt spray, and environmental particulate matter, all of which depend on the location of the turbine. Such contamination leads to several problematic issues, including accelerated bearing and gear wear, significant efficiency losses, and lubrication degradation. 

Spring Energized Teflon Seals

Traditional sealing solutions, such as lip seals and metal labyrinth seals, often fail short in long-term wind turbine use. 

Polymer Labyrinth Seals for Wind Turbine Gearboxes

Labyrinth seals address sealing challenges with a non-contact design that forms a tortuous path to block ingress and retain lubrication without generating friction, heat, or wear. Most contaminants and lubrication will lose their kinetic energy before they are able to traverse the entire labyrinth. This design makes it extremely difficult for dust, moisture, or lubricant to move in or out. The fact that it is non-contact means that it does not add any friction and eliminates the heat generated and energy loss associated with it.

When PTFE, PEEK, and Torlon labyrinth seals are used in place of metal, the final result is a lightweight, corrosion-resistant seal that can stand up to harsh conditions while keeping friction and wear to a minimum. In addition, these polymers support more design freedom when it comes to geometries as well as excellent tribological performance even under the harsh environments associated with wind turbine gearboxes. 

These non-contact seals prevent contamination and lubrication by making it almost impossible to pass through the labyrinth without losing energy, extend the service of the wind turbines, and support less frequent (and often dangerous) maintenance. 

Performance Benefits in Wind Turbine Gearboxes

Polymer labyrinth seals are ideal solutions for wind turbine gearboxes. They are non-contact solutions, which eliminate the friction and wear experienced by traditional lip seals. This also means that the gearboxes will not suffer a loss of efficiency related to seal wear, as well as the accelerated wear associated with the ingress of problematic contamination and the problematic loss of lubrication. Because they are polymers and have excellent chemical compatibility, corrosion issues are eliminated. Polymer labyrinth seals are also resistant to ozone aging, depending on the type of material selected.

The effectiveness and long life of these polymeric seals extend the service life of wind turbine gearboxes. This also reduces the costly downtime and logistics associated with repair and regular maintenance.

Conclusion

Polymer labyrinth seals are a critical reliability upgrade for wind turbine gearboxes, with benefits that include extended service life, reduced downtime, and lower maintenance costs. The combination of a non-contact seal with engineering polymers leads to an excellent solution for the numerous sources of contamination that could otherwise destroy a wind turbine gearbox.

If you are working on a new wind turbine or seeking to upgrade existing wind turbines, it is hard to go wrong with high-quality polymer labyrinth seals. And that happens to be one of our specialities at Advanced EMC.