Huahao Sealing · Carbon Graphite Components
Antimony-impregnated graphite withstands 500°C; resin-impregnated graphite is limited to 220°C. This article compares temperature, strength, thermal conductivity, corrosion resistance, and cost to guide high-temperature pump seal and bearing selection.
Carbon graphite substrates are impregnated to fill porosity and boost density and strength. Antimony and resin impregnation are the two mainstream routes, with a more than twofold difference in temperature ceiling that defines the operating envelope. Choosing the wrong grade causes impregnant carbonization and seal-face pressure loss at high temperature. This comparison quantifies 8 key parameters and gives a selection conclusion.
| Property | Antimony-Impregnated (M106H-Sb) | Resin-Impregnated (M106H) |
|---|---|---|
| Max service temperature | 500°C | 220°C |
| Compressive strength | 120 MPa | 92 MPa |
| Flexural strength | 45 MPa | 38 MPa |
| Thermal conductivity | 70 W/(m·K) | 45 W/(m·K) |
| Shore hardness | 82 HS | 78 HS |
| Steam / thermal oil resistance | ✓ | ◐ (≤220°C) |
| Strong acid / alkali resistance | ◐ | ✓ |
| Relative cost | ×1.8 | ×1.0 |
When operating temperature exceeds 220°C (thermal oil pumps, molten salt pumps, high-temp oven shafts, steam valves), antimony-impregnated graphite (M106H-Sb) is mandatory — its 500°C ceiling and higher thermal conductivity prevent impregnant carbonization. For ambient strong acid/alkali media below 220°C, resin-impregnated graphite (M106H) offers better corrosion resistance at lower cost. Both are self-lubricating, grease-free, and protect the shaft.
Antimony melts at 630.6°C, far above the carbonization point of resin (~250–300°C). The antimony metal fills graphite pores to form a high-temperature skeleton that does not decompose or volatilize during continuous 500°C operation, so its temperature ceiling is more than double that of resin impregnation.
Only in low-pressure saturated steam below 220°C. In superheated steam or above 220°C the resin gradually carbonizes, becomes brittle, and the seal face loses pressure and leaks. Switch to antimony-impregnated graphite in such cases.
Resin-impregnated graphite is more corrosion-resistant in ambient strong acids and alkalis. Antimony-impregnated graphite, containing metallic antimony, is slightly less resistant in strong oxidizing acids (e.g. concentrated nitric acid) but more stable in medium-to-high temperature water/oil service.
No. Antimony is a heavy metal and must not be used in food or pharmaceutical hygienic service. For food-grade applications choose the M106K (FDA-certified resin-impregnated) grade.
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