hBN (Hexagonal Boron Nitride): The White Graphite Solid Lubricant
When a lubricant formulator says "I need a solid lubricant that won't stain my product black" — the answer is always hexagonal Boron Nitride (hBN). Nicknamed "White Graphite," hBN is the only major solid lubricant that is naturally white, making it indispensable for food-grade greases, clean-room lubricants, electrical contact applications, and high-temperature formulations where both black discoloration and conventional PTFE are unacceptable. This guide explains what hBN is, why its unique combination of properties matters, and how to choose the right grade for your formulation.
What Is Hexagonal Boron Nitride (hBN)?
Hexagonal Boron Nitride (hBN, CAS 10043-11-5) is a synthetic inorganic compound with the chemical formula BN. It has a layered hexagonal crystal structure — each layer consists of boron and nitrogen atoms in alternating positions within a flat, hexagonal lattice, identical in geometry to graphene. Weak van der Waals forces between layers allow them to slide easily under shear stress, creating the lubricating effect. hBN is produced by high-temperature synthesis (typically 1,500–2,000°C) from boric acid and nitrogen-containing compounds.
Powderful Solutions supplies hBN in grades from D90 0.4 µm (sub-micron) to D90 2.5 µm (micron), as dry powders (Solidex B004, B025, B004M) and as pre-dispersed concentrates in PAO and vegetable ester carriers (Lubricore B230, B250, B260).
Why Is It Called "White Graphite"?
The "White Graphite" name refers to three parallel characteristics between hBN and graphite: (1) identical hexagonal platelet crystal structure, (2) similar lubrication mechanism through interlayer shear, and (3) similar thermal conductivity along the basal plane. The "white" distinguishes the most critical difference — graphite is black (dark grey), MoS2 is black, WS2 is dark grey. hBN is white, giving formulators a solid lubricant that doesn't darken their product.
Beyond the visual analogy, hBN dramatically outperforms graphite in temperature stability (900°C vs 500°C in air), chemical inertness, and electrical properties. Graphite is electrically conductive; hBN is electrically insulating — a critical distinction for applications in electrical systems.
Key Properties of hBN
| Property | Value |
|---|---|
| CAS Number | 10043-11-5 |
| Color | White |
| Crystal structure | Hexagonal (2H-BN) |
| COF (dry) | 0.15–0.70 |
| COF (lubricated) | 0.10–0.30 |
| Max temp (air) | 900°C |
| Max temp (vacuum) | 1,800°C |
| Thermal conductivity | 30–300 W/m·K (anisotropic) |
| Electrical resistivity | >10¹⁴ Ω·cm (insulating) |
| Density | 2.1 g/cm³ |
| Chemical stability | Excellent — resistant to most acids, alkalis, organic solvents |
| Humidity stability | Excellent (unlike MoS2) |
hBN vs Graphite as a Solid Lubricant
Graphite and hBN share structural geometry but differ in nearly every performance metric that matters to a lubricant formulator:
- Temperature: hBN stable to 900°C (air); graphite oxidizes above 500°C
- Electrical: hBN is insulating; graphite is conductive (causes galvanic corrosion risk)
- Color: hBN is white; graphite is black — critical for light-colored formulations
- Chemical inertness: hBN resists most chemicals; graphite is reactive with strong oxidizers
- Friction: Graphite performs similarly in humid air; hBN is less sensitive to atmosphere
For food-grade, electrical, and high-temperature applications, hBN is unambiguously superior to graphite.
hBN vs MoS2 in Lubrication
MoS2 and hBN are often compared because both are common solid lubricants. The key differences: MoS2 provides lower friction (COF 0.05–0.10 vs hBN's 0.15–0.70), but hBN withstands 900°C vs MoS2's 400°C and remains white vs MoS2's black. For applications running above 400°C in air, hBN is the only viable choice. For light-colored formulations at any temperature, hBN is mandatory.
Primary Application Areas
- Food-grade greases (NSF HX1): White color + chemical inertness + no toxicity → Lubricore B250 (vegetable ester) is specifically designed for food-contact applications
- High-temperature bearings: Industrial oven conveyors, furnace components, glass manufacturing equipment operating at 400–900°C
- Electrical connector lubricants: hBN is insulating, preventing short circuits and galvanic corrosion in electrical contact grease
- Clean-room and semiconductor: White, non-contaminating, no outgassing
- Release agents and mold lubricants: High-temperature metal forming, glass fiber production, die casting
- Cosmetic and personal care: White powder with lubrication properties used as a cosmetic-grade additive
Particle Size Guide for hBN
D90 0.4 µm (Solidex B004, Lubricore B230/B250/B260): Oil and grease additive applications, electrical contact lubricants, food-grade greases. Maximum surface area and stability in suspension.
D90 2.5 µm (Solidex B025): Release agents, high-temperature coatings, open gear applications where larger particle size provides better surface coverage on rough substrates.
Modified hBN (Solidex B004M): Surface-treated for improved compatibility with specific base oil chemistries or polymer matrices.
Powderful Solutions hBN Products
- Solidex B004: hBN powder, D90 0.4 µm — dry powder for formulation
- Solidex B025: hBN powder, D90 2.5 µm — coarser grade for coatings
- Solidex B004M: Modified hBN powder — surface-treated
- Lubricore B230: 30% hBN in PAO-6 — ready-to-blend concentrate
- Lubricore B250: 25% hBN in vegetable ester — biodegradable, food-safe
- Lubricore B260: 25% hBN in vegetable ester, D90 2.5 µm — heavy-duty
FAQ
Q: Is hBN safe for food-contact applications?
A: Yes. hBN is chemically inert, non-toxic, and approved for use in NSF HX1 lubricants. Lubricore B250 is specifically formulated in food-grade vegetable ester for direct food-contact applications. See: Lubricore B250 product page.
Q: Can hBN replace PTFE in grease?
A: hBN is a viable PTFE alternative in white-grease formulations where PFAS-free compliance is required. Its COF is slightly higher than PTFE (0.15–0.30 vs 0.05 for PTFE) but it has superior temperature stability (900°C vs 260°C) and no per- or polyfluoroalkyl chemistry.
Q: Does hBN conduct electricity?
A: No — hBN has electrical resistivity exceeding 10¹⁴ Ω·cm, making it one of the strongest electrical insulators among solid lubricants. This is the opposite of graphite and a key advantage over MoS2 (which is a semiconductor) in electrical contact applications.
Q: What is the difference between hBN and cubic boron nitride (cBN)?
A: Hexagonal BN (hBN) and cubic BN (cBN) are different crystal forms of boron nitride. hBN is the soft, lubricating form (like graphite). cBN is the hard, abrasive form (like diamond) — one of the hardest materials known. They are not interchangeable.
Powderful Solutions provides hBN samples in all grades — dry powders and pre-dispersed concentrates. TDS and SDS available immediately. Request samples →