PA (Polyamide/Nylon): The Complete Guide to a Versatile Engineering Plastic | Polypac

PA (Polyamide/Nylon): The Durable and Versatile Engineering Plastic for Demanding Applications

In the spectrum of high-performance polymers, PA (Polyamide), universally known as Nylon, stands as one of the most versatile and widely used engineering thermoplastics. Renowned for its exceptional toughness, wear resistance, and good mechanical properties, PA has evolved far beyond its textile origins to become a cornerstone material for precision mechanical components. From silent-running gears to durable wear strips in heavy machinery, PA components provide the strength, longevity, and reliability that modern industry demands.

At Polypac, with our ISO 9001 & IATF 16949 certified expertise in engineered polymer solutions, we understand and utilize the full potential of PA to create robust components for sealing systems and mechanical assemblies. This guide explores the different types of PA, their key properties, and why they are often the ideal choice for challenging applications.

What is PA (Polyamide)?

PA is a family of synthetic thermoplastics characterized by repeating amide groups in their molecular chain. This structure gives them high strength and durability. The most common types are PA6 and PA66, with numbers indicating the number of carbon atoms in the monomer units.

In industrial applications, PA is valued for its role in creating:

1. High-Strength Structural Parts: Housings, brackets, and fasteners.

2. Wear-Resistant Moving Components: Gears, bushings, rollers, and slides.

3. Critical Support Elements in Fluid Systems: Wear rings, guide strips, and bearing pads in cylinders and machinery.

Key Properties and Advantages of PA (Nylon)

PA's balanced property profile makes it a default choice for countless engineering challenges:

1. High Strength, Toughness, and Stiffness

PA offers an excellent strength-to-weight ratio with good impact resistance, even at low temperatures. It can withstand significant mechanical stress without failure.

2. Outstanding Wear and Abrasion Resistance

This is one of PA's standout features. It has excellent resistance to wearing, making it ideal for components in frictional contact with metals or other surfaces, often outperforming many other plastics.

3. Good Chemical Resistance

Resistant to many oils, greases, fuels, and solvents. This makes it suitable for use in automotive, hydraulic, and industrial environments. It is not recommended for strong acids or oxidizing agents.

4. Low Coefficient of Friction

PA has good inherent lubricity, allowing for smooth operation in bearings and sliding applications, often with minimal need for external lubrication.

5. Temperature Resistance

Continuous service temperature typically ranges from -40°C to +120°C, depending on the grade and load. Glass-filled grades can withstand higher temperatures.

6. Electrical Insulation

PA is an excellent electrical insulator, adding to its versatility in electromechanical applications.

Common Types and Enhanced Grades of PA

• PA6 (Nylon 6): Known for its toughness, impact resistance, and slightly better surface finish. It is generally more flexible than PA66.

• PA66 (Nylon 66): Offers higher strength, stiffness, and thermal resistance compared to PA6, but can be slightly more brittle.

• Glass-Filled PA (e.g., PA6-GF30): The addition of glass fibers dramatically increases tensile strength, stiffness, and heat deflection temperature, while reducing creep and moisture absorption effects. This is a common choice for high-stress structural parts.

• MoS2 (Molybdenum Disulfide) Filled PA: Adds solid lubrication, further reducing friction and wear, ideal for high-load, low-speed bearing applications.

• Oil-Filled Nylon: Impregnated with oil to provide permanent internal lubrication, significantly reducing friction and wear from the start.

The Critical Role of PA in Sealing and Fluid Power Systems

While not a sealing elastomer itself, PA is indispensable in sealing system reliability:

1. Wear Rings / Guide Strips: PA wear rings, especially glass-filled grades, are extensively used in hydraulic and pneumatic cylinders. They are installed on pistons and rods to:

   • Absorb radial loads and prevent metal-to-metal contact.

   • Guide and align the piston and rod, ensuring the primary seals (U-cups, rod seals) work under ideal conditions, free from misalignment that causes premature failure.

   • Provide a low-friction, wear-resistant sliding surface.

2. Piston Rings and Bearing Pads: In certain cylinder designs, PA components act as the primary bearing surface for the piston.

3. Gears and Bushings in Pump/Motor Drives: Used in the mechanical drives of hydraulic pumps and motors, where resistance to wear and compatibility with lubricating oils is critical.

Important Considerations: Understanding Moisture Absorption

The most significant factor to consider with PA is its hygroscopic nature—it absorbs moisture from the air. This affects it in two ways:

• Dimensional Change: As PA absorbs water, it swells. A part machined from dry stock will grow in size when placed in a humid environment. This must be accounted for in precision applications, often by conditioning the material to the service environment before final machining or using stabilized grades.

• Property Change: Moisture absorption plasticizes PA, increasing its toughness and impact resistance while slightly reducing its strength and stiffness.

The Polypac Advantage: Engineering with Knowledge

We don't just supply PA parts; we provide solutions based on a deep understanding of the material's behavior.

• Informed Material Selection: We help you choose the right PA grade (PA6 vs. PA66, filled vs. unfilled) based on your application's need for strength, wear, temperature, and dimensional stability.

• Precision Machining with Foresight: Our machining expertise accounts for PA's characteristics. For critical components like wear rings, we understand tolerancing relative to moisture content to ensure a perfect fit in the final operating environment.

• Quality Components for Demanding Systems: We supply high-quality PA wear strips, guide rings, and custom machined parts that meet the rigorous demands of hydraulic, pneumatic, and general mechanical systems.