Topic: Cast Nylon Grade Selection
Material Family: Mitsubishi Chemical Nylatron® (Cast PA6)
Grades Covered: Nylatron GSM, GSM Blue, NSM, 703XL
Common Applications: Wear Pads, Bushings, Sheaves, Bearings, Slide Components
Cast Nylon Grades: One Polymer, Different Performance Windows
Cast nylon (PA6) is a versatile engineering plastic widely used in industrial wear components such as sheaves, bushings, wear pads, and bearings. Although each material is based on the same PA6 chemistry, the grade-specific additives and molecular structure significantly change the way the material performs in load-bearing, sliding, and wear environments.
The Mitsubishi Chemical Nylatron® family represents several graduated performance levels, each engineered to achieve a balance of wear life, load capacity (PV limit), friction behavior, and durability for different application environments. We will be reviewing four different grades of the Nylatron® family of products:
- Nylatron® GSM
- Nylatron® GSM Blue
- Nylatron® NSM
- Nylatron® 703XL
Understanding Application Requirements
Before choosing a grade, component designers typically look at three primary criteria.
1. Wear Life (K-Factor)
The K-factor is a lab measurement that reflects how much material wears away per unit of pressure and velocity (PV).
Lower K-Factor = Longer Wear Life. This metric becomes critical for high-cycle applications, especially bushings on pivot points or bearings running continuously under load.
| Grade | Relative Wear Life |
|---|---|
| GSM | Standard bearing-grade baseline |
| GSM Blue | Reduced friction → improved wear |
| NSM | Premium wear resistance + lowest CoF |
| 703XL | Prioritizes friction control over wear maximization |
2. Load Capacity / PV Limits
PV (Pressure × Velocity) defines the operating window where a bearing surface can survive without overheating or deforming.
Higher PV = the ability to handle more load at speed without failure.
| Grade | Limiting PV |
|---|---|
| GSM | ~3,000 |
| GSM Blue | ~5,500 |
| NSM | ~15,000 |
| 703XL | ~17,000 |
This metric is why you see:
- Standard GSM used in moderate-load sliding parts
- GSM Blue used for higher-duty bearings and wear components
- NSM/703XL chosen when loads are high, lubrication is inconsistent, or uptime is critical
3. Coefficient of Friction (CoF)
Coefficient of Friction (CoF) defines how easily two surfaces slide against each other. In bearing and sliding applications, a lower CoF means reduced frictional resistance, which directly translates into:
- Lower heat generation
- Less surface scoring on shafts or wire rope
- Longer wear life of the nylon component
- Reduced energy loss during movement
- Improved performance under limited lubrication
In cast nylon, CoF is controlled through the type and volume of internal lubricant additives blended into the material. While all grades start with the same PA6 base chemistry, the addition of solid lubricants such as molybdenum disulfide (MoS₂) and proprietary internal lubricants creates a measurable improvement in performance.
- Nylatron® GSM reduces friction versus unfilled nylon through MoS₂ reinforcement, making it a reliable general-purpose bearing material.
- Nylatron® GSM Blue incorporates a proprietary internal lubricant system that significantly lowers CoF and keeps the friction film stable, delivering longer wear life in rotating applications versus conventional moly-filled nylon.
- Nylatron® NSM offers low CoF and high load-handling capabilities, maintaining a stable lubrication layer even under dry-running conditions. This is critical in heavy-duty components, high-load bushings, winch rollers, and marine environments where re-greasing intervals are lengthy.
- Nylatron® 703XL is engineered not only to lower CoF, but to control the friction curve during slow-speed startup, preventing stick-slip, vibration, and chatter — making it the optimal grade for precision linear motion and controlled-movement systems.
Grade-by-Grade Application Summary
Nylatron® GSM — Base Moly-Filled Cast Nylon
Use Case: General purpose wear parts
Why Use It: Balance of cost and performance
Applications: Industrial bushings, sheaves, wear strips, guide blocks
GSM is reinforced with molybdenum disulfide (MoS₂), which improves the wear resistance and load-carrying capability of standard cast Nylon 6. This additive reduces surface friction, promotes cleaner running at the contact interface, and increases the material’s ability to handle higher bearing pressures without excessive wear or softening.
Nylatron® GSM Blue — Premium Internal Lubricant System
Use Case: Long wear life under continuous duty
Why Use It: Lower friction, cooler running, and longer wear life than standard moly-filled nylon in high-cycle applications
Applications: Sheaves, wire rope rollers, high-cycle bushings, sliding pads
GSM Blue incorporates a proprietary internal lubricant system that significantly lowers friction and improves load-carrying efficiency compared to conventional moly-filled nylon. This additive package forms a uniform, low-friction transfer film at the wear interface, reducing surface temperature and dramatically extending wear life.
Nylatron® NSM — Extreme-Duty, Self-Lubricating Formulation
Use Case: High load + low lubrication + long uptime
Why Use It: High limiting PV rating, minimal wear at contact points, 8× better than conventional moly-filled nylon
Applications: Steel mill bearings exposed to heat, load, debris, and inconsistent lubrication; continuous-rotation bushings on critical motion points; marine equipment exposed to saltwater, contamination, and long maintenance intervals; press bearings operating under shock load and repetitive cycling
NSM is often selected as the true metal-replacement grade for demanding bearing environments. It delivers bronze-like durability in dry-running conditions while adding benefits that metals cannot provide.
Nylatron® 703XL — Controlled Friction, Smooth Startup Stability
Use Case: Applications sensitive to stick-slip and precision motion
Why Use It: The formulation controls friction during low-speed startup and eliminates chatter, stick-slip, or vibration
Applications: Linear bearing surfaces, motion controls, precision wear pads, and tension wheels
703XL distinguishes itself not by raw PV rating alone, but by its motion quality. The material is selected when the accuracy, smoothness, and repeatability of movement have greater impact on system performance. This formulation closes the gap between dynamic and static coefficients of friction.
Need help choosing the right Nylatron grade for your application? Send us a print or connect with our engineering team for a material recommendation.
Frequently Asked Questions
What is cast nylon (PA6)?
Cast nylon is a thermoplastic engineering polymer (polyamide 6) produced by polymerizing caprolactam directly in a mold rather than melt-extruding a finished pellet. The casting process produces larger, denser stock shapes with higher molecular weight than extruded nylon, giving it superior wear resistance, dimensional stability, and load-carrying capability for industrial bearings, bushings, sheaves, and wear components.
What is the difference between Nylatron GSM and Nylatron GSM Blue?
Nylatron GSM is reinforced with molybdenum disulfide (MoS₂) for general-purpose wear performance. Nylatron GSM Blue uses a proprietary internal lubricant system that produces a lower coefficient of friction, cooler running temperatures, and significantly longer wear life. GSM Blue typically outperforms standard moly-filled nylon in high-cycle bearing and sheave applications.
What does PV limit mean for a plastic bearing material?
PV limit is the maximum combination of pressure and surface velocity a bearing material can sustain without overheating, melting, or excessive wear. It is calculated by multiplying the load on the bearing face (P) by the sliding speed (V). A higher PV limit means the material can carry more load at higher speeds before failure occurs.
Which Nylatron grade is best for high-load, dry-running bearings?
Nylatron NSM is the preferred choice for high-load, dry-running, or poorly lubricated bearings. With a limiting PV of approximately 15,000 and roughly 8× the wear life of conventional moly-filled nylon, it maintains a stable lubrication film even without re-greasing — making it a common bronze replacement in steel mill, marine, and press equipment applications.
Why does Nylatron 703XL prevent stick-slip in precision motion systems?
Nylatron 703XL is formulated to narrow the gap between static and dynamic coefficients of friction. In most plastics, the static CoF is meaningfully higher than the dynamic CoF, which causes a jolt at startup known as stick-slip. By balancing the two values, 703XL produces smooth, controlled motion at low speeds, eliminating chatter and vibration in linear bearings and motion control systems.
Can Nylatron cast nylon replace bronze bearings?
Yes — particularly Nylatron NSM and 703XL. Both grades deliver bronze-comparable load capacity in dry-running conditions while adding benefits metals cannot provide: lower weight, no corrosion, no shaft scoring, no need for grease, and significantly quieter operation. Cast nylon also absorbs shock load and vibration better than bronze, extending the life of mating components.
How is the K-factor used to compare wear plastics?
The K-factor measures volumetric material loss per unit of pressure and velocity over time, expressed in standardized lab conditions. A lower K-factor indicates a longer-lasting wear surface. Engineers use K-factor alongside PV limit and CoF to compare bearing-grade plastics, since no single metric fully captures real-world performance under varying load and speed.