Material
PEEK PEEK
The structural metal-replacement polymer. Machines like plastic, carries load like a light alloy, survives chemicals and steam that destroy other polymers, and costs a great deal per pound.
Overview
Polyetheretherketone is the highest volume of the true high-performance thermoplastics and the one most often specified to take weight out of a metal bracket. It is semi-crystalline, which gives it real chemical and solvent resistance rather than the stress cracking that limits amorphous polymers, and it holds useful strength to around 250 degrees Celsius. Glass and carbon filled grades roughly double stiffness and are the ones usually used structurally. In defense it appears wherever a metal part can lose weight without losing function: clips, brackets, bushings, connector bodies, and increasingly as the matrix in thermoplastic composite structure. It is also the base polymer behind a large share of implantable medical hardware, which sustains a supply base the defense sector benefits from.
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Defense applications
Metal replacement brackets and clips
Structural clips, brackets and standoffs where a light alloy part can be replaced at lower weight, with electrical isolation and no corrosion as bonus properties.
Cable clips and standoffs, Structural brackets, Insulating spacers, Wear pads
Bearings, bushings and seals
Unlubricated bearing surfaces where PEEK runs against metal without galling, and where a metal bushing would need lubrication that cannot be maintained.
Bushings and wear rings, Back-up rings, Seal components, Thrust washers
Connector bodies and electrical hardware
Housings and insulators needing dimensional stability, flame resistance and electrical isolation at temperature.
Connector housings, Terminal blocks, Insulating hardware
Thermoplastic composite matrix
As the matrix in carbon fiber thermoplastic tape, where it enables welded rather than bonded assembly and removes prepreg out-time entirely.
Welded aerostructure, Clips and brackets from composite tape, Ducting
Alloys and grades
| Designation | Grade | Class | Notes | Typical forms |
|---|---|---|---|---|
| Unfilled PEEK | Natural or virgin polyetheretherketone | The base grade, used where chemical resistance, electrical isolation or purity matter more than stiffness. | Polymer Resin, Stock Shape, Molded Component | |
| 30% Glass Filled PEEK | Glass fiber reinforced PEEK | Roughly doubles stiffness and improves dimensional stability at temperature, while remaining electrically insulating. | Polymer Resin, Stock Shape, Molded Component | |
| 30% Carbon Filled PEEK | Carbon fiber reinforced PEEK | Highest stiffness and strength of the common grades, with improved thermal conductivity and wear. Electrically conductive, which rules it out of insulating applications. | Polymer Resin, Stock Shape, Molded Component | |
| Bearing Grade PEEK | PEEK with PTFE, graphite and carbon fiber | Compounded specifically for unlubricated sliding, trading strength for a much lower friction coefficient. | Stock Shape, Molded Component |
Properties
| Property | Value | Unit | Note |
|---|---|---|---|
| Density | 1.30 to 1.32 | g/cm3 | Unfilled; roughly half aluminium and a sixth of steel |
| Tensile strength, unfilled | 90 to 100 | MPa | Around 14 ksi |
| Tensile strength, 30% carbon filled | approximately 200 to 240 | MPa | Filled grades are the structural ones |
| Glass transition temperature | 143 | degrees C | |
| Melting point | 343 | degrees C | Semi-crystalline, which is why it resists solvents |
| Continuous service temperature | approximately 250 | degrees C | Far above most engineering polymers |
| Water absorption | Very low | Around 0.5 percent, so dimensions stay stable | |
| Flammability | Inherently flame retardant | Low smoke and toxicity, which matters in enclosed spaces |
Advantages
- Highest strength and temperature capability of the readily machinable thermoplastics
- Excellent chemical and solvent resistance because it is semi-crystalline
- Inherently flame retardant with low smoke and toxicity
- Runs unlubricated against metal without galling
- Electrically insulating, non-magnetic and corrosion immune
- Available as resin for moulding and as stock shape for machining, so both volumes are served
- Sterilisable and biocompatible, sustaining a large adjacent medical supply base
Limitations
- Expensive per pound, often 50 to 100 times commodity engineering plastics
- Resin production is concentrated in very few global producers
- High processing temperature demands specialised moulding and extrusion equipment
- Stock shape machining releases internal stress, so annealing and careful fixturing are required
- Loses stiffness sharply above the glass transition temperature
- Ultraviolet resistance is poor without additives
Governing specifications
| Designation | Body | Scope |
|---|---|---|
| ASTM D6262 | ASTM International | Polyetheretherketone resins and moulding compounds |
| SAE AMS 3660 | SAE International | Related aerospace polymer material specifications |
| UL 94 V-0 | Underwriters Laboratories | Flammability classification, which PEEK meets without additives |