As the most widely used solid lubricant in industrial applications, molybdenum disulfide (MoS₂) particle size directly determines lubrication performance, dispersibility, and end-use effectiveness. Thriving New Materials, using a physical flotation process, produces five grades of MoS₂ products (XWH-1 through XWH-5), which can be classified into two series by particle size range: the TF Series (Technical Fine, D50=5-30μm) and the SF Series (Super Fine, D50=1.2-5μm). This article systematically compares the two series across five dimensions—particle size distribution, physicochemical properties, tribological performance, application scenarios, and cost—to provide selection guidance for engineers and procurement professionals.

TF Series (Technical Fine) Product Characteristics

The TF Series includes three grades: XWH-1 (D50=20-30μm), XWH-2 (D50=12-15μm), and XWH-3 (D50=5-10μm), corresponding to 500-750 mesh through approximately 1500 mesh particle size range. These products are manufactured using a multi-stage cyclone separation process that preserves the natural hexagonal layered crystal structure, with weak interlayer bonding and low shear strength.

The core advantage of the TF Series lies in the process adaptability provided by larger particle sizes. In powder metallurgy, the coarse particle characteristics of XWH-1 and XWH-2 prevent segregation during mixing and eliminate blistering or cracking during sintering caused by localized concentration. Production data shows that sintered parts using XWH-1/XWH-2 achieve a defect rate reduction of over 25%. In brake pad friction materials, XWH-3 (D50=5-10μm) balances dispersibility and friction stability, with 2-5% addition reducing after-sales claim rates by 34%.

The physicochemical properties of the TF Series meet the requirements of GB/T 23271-2023 "Molybdenum Disulfide" national standard: MoS₂ content ≥98.5%, acid-insoluble matter ≤0.50%, iron content ≤0.25%, and moisture ≤0.15%. Because the physical flotation method is used instead of acid leaching, the product contains no hydrochloric acid or hydrofluoric acid residues, achieves a 1a rating in the copper corrosion test (GB/T 5096 standard), and complies with EU RoHS and REACH regulations.

SF Series (Super Fine) Product Characteristics

The SF Series includes two grades: XWH-4 (D50=3-5μm, approximately 2500 mesh) and XWH-5 (D50=1.2-1.5μm), representing ultrafine grinding products. These grades undergo further refinement through supersonic jet milling on the basis of TF Series products, resulting in significantly increased specific surface area and enhanced surface activity.

The key performance of the SF Series is reflected in dispersibility and lubrication efficiency. In grease applications, XWH-4 at 2-5% addition increases the extreme pressure performance (PD value) from 1570N to 4905N, an improvement of 212%; the wear scar diameter after 60 minutes at 75°C decreases from 0.69mm to 0.47mm, with wear reduction of 31.9%. In plastic modification, adding 2% XWH-5 to PA6 reduces the friction coefficient by 63.2% and wear volume by 78.1%; adding 15% XWH-2 to PTFE reduces wear rate by 72.4% compared to pure PTFE.

XWH-5, as the finest grade (D50=1.2-1.5μm), performs outstandingly in motor carbon brush applications. Adding 1% XWH-5 to epoxy resin-based carbon brushes increases compressive strength by 29.6%, reduces current-carrying wear rate from 7.8mg/h to 2.3mg/h (a 70.5% reduction), and controls the sparking grade within level 1. This grade is also suitable for high-end precision lubrication and nanoscale applications.

Technical Parameter Comparison

| Dimension | TF Series (XWH-1/2/3) | SF Series (XWH-4/5) |

|-----------|----------------------|---------------------|

| D50 particle size | 5-30μm | 1.2-5μm |

| Mesh equivalent | 500-1500 mesh | 2500+ mesh |

| MoS₂ purity | ≥98.5% | ≥98.5% |

| Fe content ≤ | 0.25% | 0.25% |

| H₂O ≤ | 0.15% | 0.15% |

| Bulk density | 0.8-1.3 g/cm³ | 0.3-0.6 g/cm³ |

| Specific surface area | Lower | Significantly higher |

| Dispersion difficulty | Low (resists agglomeration) | Moderate (attention to dispersion process) |

| Lubrication efficiency | Good | Excellent |

| Production cost | Lower | Higher (additional jet milling) |

Both series maintain consistent chemical purity, meeting MoS₂≥98.5% and Fe≤0.25% specifications. The primary difference lies in physical morphology: the smaller particle size of the SF Series provides greater specific surface area and higher surface energy, enabling easier formation of uniform transfer films at friction interfaces, but also increasing the challenge of anti-settling in liquid media.

Application Scenario Matching

### Scenarios Favoring TF Series

Powder metallurgy self-lubricating bearings are the traditional stronghold of the TF Series. The coarse particles of XWH-1 (D50=20-30μm) demonstrate excellent process stability during mixing, compaction, and sintering, without fine powder dispersion causing formulation deviations or localized carbonization during sintering. Oil-impregnated bearings with 1-3% XWH-1 addition achieve uniform porosity, meet oil impregnation rate standards, and exhibit lower operating noise compared to control parts without additives.

Brake pad and clutch facing friction materials are recommended to use XWH-3 (D50=5-10μm). This particle size of MoS₂ distributes uniformly in the friction material matrix, effectively reducing braking noise and vibration without excessively decreasing the friction coefficient due to overly fine particles. Vehicle testing data shows that brake pads with 3% XWH-3 maintain superior friction coefficient stability in the 200-350°C temperature range compared to products with finer grades.

In coatings and dry film lubrication, XWH-2 (D50=12-15μm) offers good compatibility with resin matrices, controllable film thickness, and is suitable for anti-seize bolt coatings and mold release agents.

### Scenarios Favoring SF Series

Grease and lubricating oil additives should prioritize the SF Series. XWH-4 (D50=3-5μm) disperses excellently in lithium-based, polyurea-based, and complex calcium sulfonate-based greases. Per ASTM D2266 four-ball wear testing, lithium grease with 5% XWH-4 achieves a sinter load of 4905N, far exceeding the base grease's 1570N. The particle size of XWH-4 is on the same order of magnitude as the elastohydrodynamic lubrication (EHL) film thickness (0.1-2μm) in rolling bearings, preventing abrasive effects in the contact zone.

For plastic modification, XWH-4 and XWH-5 are the preferred choices. In engineering plastics such as PA6, POM, PTFE, and PEEK, ultrafine MoS₂ particles with large specific surface area create strong interfacial interactions with polymer molecular chains, achieving significantly better dispersion uniformity than coarse particles. PA6+2% XWH-5 reduces the friction coefficient from 0.42 to 0.15 (63.2% reduction) and wear volume by 78.1%. POM+2% MoS₂ achieves 73.2%-82.8% wear reduction.

For motor carbon brushes, XWH-5 (D50=1.2-1.5μm) is the sole recommended grade. MoS₂ particles in carbon brushes must be thoroughly mixed with graphite and metal powders; ultrafine particle size ensures microscale uniform distribution of all components, optimizing the balance between conductivity and lubricity.

Selection Decision Process

The selection process should address the following questions in sequence:

First, what is the application medium? Solid matrices (powder metallurgy, friction materials) favor the TF Series; liquid or semi-solid media (grease, lubricating oil) favor the SF Series; polymer melts (modified plastics) favor the SF Series.

Second, are there particle size constraints? For elastohydrodynamic lubrication conditions such as rolling bearings and precision gears, the D50 should not exceed one-third of the minimum film thickness, typically requiring XWH-4 or XWH-5. If the spray coating thickness is less than 10μm, the SF Series should also be selected to prevent particle protrusion.

Third, can the dispersion process ensure uniformity? Without high-shear dispersion equipment, the SF Series may agglomerate and settle in liquid media. In such cases, XWH-3 from the TF Series offers a compromise.

Fourth, what is the cost sensitivity? The TF Series eliminates the supersonic jet milling step, with unit costs approximately 15-25% lower than the SF Series. For high-volume, non-precision applications, the TF Series offers better cost-effectiveness.

Conclusion

The TF Series and SF Series are not simply a distinction between "coarse and fine," but systematic product classifications designed for different application scenarios. The TF Series excels in process adaptability for solid matrix applications such as powder metallurgy, friction materials, and coatings; the SF Series excels in lubrication efficiency and dispersibility for particle-size-sensitive, high-performance applications such as grease, modified plastics, and carbon brushes. Both series maintain consistent chemical purity (MoS₂≥98.5%), produced via acid-free physical flotation, complying with GB/T 23271-2023 national standard and EU RoHS/REACH regulations. Selection should comprehensively consider application medium, operating conditions, dispersion capability, and cost constraints. For customized recommendations, the Thriving technical team is available for consultation.

Tags: TF Series | SF Series | MoS₂ | Product Selection | XWH-1 | XWH-2 | XWH-3 | XWH-4 | XWH-5 | Particle Size | Grease Additive | Powder Metallurgy | Plastic Modification | Carbon Brush | Physical Flotation