DuPont Vespel Polyimide Shapes
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Vespel is the trademark of a durable high-performance polyimide-based polymer (or plastic) manufactured by DuPont.
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[edit] Characteristics and Applications
The extremely expensive polymer is mostyl used in aerospace, semiconductor and transportation technology. Vespel combines heat resistance, lubricity, dimensional stability, chemical resistance, creep resistance to become a useful plastic for use in hostile conditions,
Unlike most plastics, it does not outgas or melt , which makes it useful for lightweight heat shields and crucible support. It also performs well in vacuum applications and even in extremely low cryogenic temperatures.
Although there are polymers superseding vespel in these properties the combination is the main advantage of vespel.
[edit] Types
Vespel is produced in five standard formulations:
- SP-1
- provides operating temperatures from cryogenic to 300°C (570°F), great plasma resistance, plus a UL rating for minimal electrical and thermal conductivity. Vespel SP-1 is the unfilled base resin grade. SP-1 provides maximum physical strength, elongation, and toughness as well as the best electrical and thermal insulation values.
- SP-21
- has 15% graphite by weight added to the base resin for increased wear resistance and reduced friction in applications such as bearings, thrust washers, bushings, seal rings, slide blocks and other wear applications. Vespel SP-21 has the highest mechanical properties of the graphite filled grades.
- SP-22
- has 40% graphite by weight for enhanced wear resistance, lower friction, improved dimensional stability (low coefficient of thermal expansion), and stability against oxidation.
- SP-211
- has 10% PTFE and 15% graphite by weight added to the base resin for the lowest coefficient of friction over a wide range of operating conditions. It also has excellent wear resistance up to 149°C (300°F). Typical applications include sliding or linear bearings as well as many wear and friction uses listed above.
- SP-3
- is 15% moly-filled (molybdenum disulfide solid lubricant) for wear and friction resistance in vacuum and other moisture-free environments where graphite actually becomes abrasive. Typical applications include seals, bushings, bearings, gears, and other wear surfaces in outer space, ultra-high vacuum or dry gas applications.
Vespel is processed by both Direct-Forming (DF parts) and Isostatic Molding (basic shapes - plates, rods & tubes). For prototype quantities, basic shapes are typically used for cost efficiency since tooling is quite expensive for DF parts. For large scale cnc production, DF parts are often used to reduce per part costs, but done so at the sacrifice of material properties which are much higher on isostatically produced basic shapes. Vespel is a polyimide material & for many years was the only option for high-end polyimide parts. Vespel is a proven material in critical applications. It is also quite expensive and out of the reach of many applications due to its high cost. Recently, other polyimide materials such as Meldin, and Plavis have brought additional options in the polyimide shapes market and may help reduce the overall market cost of polyimide shapes.
