Technical Product Dossier
Celanese Hostaform® C 9021 G POM
A specialized polyoxymethylene copolymer engineered for superior low-friction and high-wear resistance in demanding applications.
Executive Summary & Identification
Introduction to Hostaform® C 9021 G
Hostaform® C 9021 G is a specialized, medium-flow injection molding grade of polyoxymethylene (POM) copolymer, engineered for applications demanding superior tribological performance. The material is supplied in pellet form, primarily for processing via injection molding, although other extrusion methods may be applicable.
The defining characteristic of this grade is denoted by the "G" suffix in its nomenclature. This signifies a tribological modification through the incorporation of GUR®, the Celanese brand of Ultra-High Molecular Weight Polyethylene (PE-UHMW). This modification fundamentally alters the material's properties from a standard POM, creating a composite system designed to deliver a low coefficient of friction and high resistance to wear. The primary engineering purpose of Hostaform® C 9021 G is for the manufacturing of components subjected to continuous or intermittent sliding contact and abrasive stress.
The base polymer is a POM copolymer, which provides a foundation of excellent chemical resistance to a wide range of substances including solvents, fuels, and strong alkalis, coupled with good hydrolytic stability and high resistance to long-term thermal and oxidative degradation. The addition of PE-UHMW builds upon this robust chemical foundation to create a self-lubricating material optimized for moving parts.
The Hostaform® C 9021 Family: A Comparative Context
To accurately evaluate and specify Hostaform® C 9021 G, it is imperative to distinguish it from other grades within the C 9021 product family. The property profiles of these materials are distinct, and misapplication of data from one grade to another can lead to critical design failures.
- Hostaform® C 9021 (Standard Grade): High rigidity (Tensile Modulus ~2850 MPa), excellent toughness, and higher melt flow (MVR ~8 cm³/10min).
- Hostaform® C 9021 G (Tribological Grade): Lower stiffness (Tensile Modulus ~2300 MPa), significantly lower impact toughness, and lower melt flow (MVR ~5.5 cm³/10min) for enhanced wear resistance.
- Hostaform® C 9021 GV Series (Glass-Reinforced): Maximum strength and stiffness (e.g., GV1/30 Tensile Modulus ~9200 MPa) for structural applications.
Critical Point for Material Selection:
Hostaform® C 9021 G is not a universally superior version of the standard C 9021. It is a highly specialized variant. An engineer mistakenly using the datasheet for the standard grade would overestimate stiffness by over 20% and toughness by over 600%, leading to a component that is weaker, more flexible, and substantially more brittle than designed.
Comprehensive Material Properties
Physical and Rheological Properties
| Property | Value | Unit | Test Standard |
|---|---|---|---|
| Density | 1340 | kg/m³ | ISO 1183 |
| Melt Volume-Flow Rate (MVR) | 5.5 | cm³/10min | ISO 1133 |
| Molding Shrinkage, parallel | 2.3 | % | ISO 294-4, 2577 |
| Molding Shrinkage, normal | 1.8 | % | ISO 294-4, 2577 |
Mechanical Performance
| Property | Value | Unit | Test Standard |
|---|---|---|---|
| Tensile Modulus | 2300 | MPa | ISO 527-1/-2 |
| Yield Stress | 45 | MPa | ISO 527-1/-2 |
| Nominal Strain at Break | 10 | % | ISO 527-1/-2 |
| Property | Value | Unit | Test Standard |
|---|---|---|---|
| Charpy Impact Strength, unnotched (+23°C) | 30 | kJ/m² | ISO 179/1eU |
| Charpy Notched Impact Strength (+23°C) | 3.5 | kJ/m² | ISO 179/1eA |
Crucial Design Consideration:
The material's impact strength drops from 30 kJ/m² (unnotched) to just 3.5 kJ/m² (notched), indicating very high notch sensitivity. Parts must be designed with generous radii and smooth surface transitions to prevent brittle failure under load.
Thermal, Flammability & Electrical Properties
Thermal
Melting Temp: 166 °C
Heat Deflection Temp (1.8 MPa): 88 °C
Flammability
UL 94 Rating: HB (Horizontal Burn)
Automotive: Meets FMVSS 302
Electrical Insulation
Volume Resistivity: 1 x 10¹² Ω·m
Comparative Tracking Index (CTI): 600 (Excellent)
Processing & Fabrication Guidelines
Injection Molding Parameters
Pre-Drying Required:
If material is exposed to moisture, dry at 100-120°C for 3-6 hours to prevent processing defects.
| Parameter | Recommended Value |
|---|---|
| Melt Temperature | 190 – 210 °C |
| Mold Temperature | 80 – 120 °C |
| Injection Speed | Slow to Medium |
Safety, Applications & Compliance
Primary Safety Hazard:
Thermal degradation above 238°C (460°F) releases formaldehyde gas. Ensure proper ventilation and temperature control during processing and wear appropriate PPE.
Primary Application Areas
Automotive
Sliding guides, gears, seat/window mechanisms.
Precision Engineering
Printer/copier parts, camera components.
Consumer Goods
Appliance gears, furniture sliders, conveyor parts.
Conclusion
Celanese Hostaform® C 9021 G is a highly specialized engineering thermoplastic, precisely formulated for applications where tribological performance is the primary design driver. The enhancement in surface properties is achieved at the expense of bulk mechanical and thermal performance, making it unsuitable for applications where high structural integrity or impact resistance are paramount.
Successful implementation hinges on a comprehensive understanding of this balance. Designers must leverage its tribological benefits while accommodating its reduced mechanical properties and high notch sensitivity. When specified correctly and processed with diligence, Hostaform® C 9021 G offers a robust and reliable solution for manufacturing durable, self-lubricating components.