POLY ETHER ETHER KETONE (PEEK):
Typical Applications
Characteristics:
1. Crystalline thermoplastic
2. Chemically resistant
3. Operates in a wide pH range (from 60% sulphuric acid to 40% sodium hydroxide) & at high temperatures
4. Additional chemical resistance includes the organic solvents, aqueous reagent, and long term performance in superheated water at 260oC.
5. Heat distortion temperature of glass filled grade 315oC. Retains mechanical properties close to its melting temperature of 343°C. Continuous service possible at 240oC
6. High mechanical properties
7. Very low smoke emission. Low flammability value of UL 94 V-0 at 1.45 mm. Limiting oxygen index of 35% at 3.2 mm. Self extinguishing characteristics
8. Unparalleled wear and friction resistance in special tribological grades
Available Grades:
1. Regular,
2. Glass-fibre filled
3. Carbon-fibre filled grades,
In critical in-engine parts, the polymer withstands high temperatures and the tribological interaction of dry and lubricated material contacts.
In aircraft exterior parts, the polymer provides excellent resistance to rain erosion, while for aircraft interior components, its inherent flame retardancy and low smoke and toxic gas emission reduce the hazard to passengers and crew in the event of a fire.
Additives:
1. The most important additives for PEEK are glass fiber and carbon fiber reinforcements.
2. As an example non-filled PEEK has an HDT of 140oC at 1.81 MPa, this value increases markedly for C-fiber reinforced PEEK, reaching a maximum at 315oC. PEK is superior with HDTs of 186oC and 360oC for non-filled and glass-fiber filled material respectively.
Thermal Properties:
1. PEEK shows a drop in properties such as modulus and strength as temperature increases.
2. PEEK is suitable for use, albeit for short periods, at temperatures in excess of 300℃.
3. Good retention of modulus is shown up to the glass-transition temperature of 143 oC. Beyond this the modulus drops sharply, but some rigidity is maintained up to the melting point of 334 oC.
4. In the case of the glass –reinforced grades, the level of rigidity is significant as evidenced as a heat-distortion temperature of 300 oC, with a fiber reinforcement level of 30%.
Electrical
1. Connectors and insulation components.
2. The combination of thermal stability and good dimensional stability at elevated temperatures, good melt process ability and good electrical properties over a wide range of temperature favor the use of PEEK in electrical and electronics engineering.
Resistance to Chemicals:
1. PEEK is resistant to most chemicals.
2. Only concentrated sulfuric acid decomposes the product.
3. Nitric acid and some halogenated hydrocarbons degrade PEEK.
4. PEEK does not hydrolyze in water even at 280°C (18 bar).
Resistance to Stress Cracking
1. Very resistant to stress cracking.
2. Hairline cracks occur only in acetone.
3. High mechanical stresses may shorten service life.
Weathering Resistance
1. PEEK is affected by the UV component in sunlight.
2. Pigmentation or lacquering of molded material is thus recommended for extreme weathering conditions. Colorants and carbon black are suitable.
Resistance to High Energy Radiation
1. PEEK shows superior radiation resistance. It withstands a g-radiation dosage of 107 J kg-1. 2. GF reinforced grades exhibit even higher resistance.
Flammability
1. Even without the addition of flame retardants, PEEK is of low flammability.
2. PEEK 450 G is classified as V-O (2 mm thick) to UL94.
3. The oxygen index is 35% and thus higher than that of polysulfone and polyimide but lower than that of polyamide-imide and PPS.
4. Smoke development is the lowest of all thermoplastics.
Processing
1. PEEK is processed by injection molding.
2. It must be pre dried at 150 °C for at least 3hours.
3. The melt temperature is 350 to 380 °C for unreinforced material and 370 to 400 °C for reinforced material. Recommended mold temperatures are 150 to 180°C.
4. Shrinkage is 1 % and 0.1 to 1.4% for the unreinforced and fiber reinforced materials, respectively.
5. Peeled film up to 20 mm can be produced from injection molded semi-finished products. These can be used in place of biaxially oriented films.
Surface Finishing
1. PEK and PEEK moldings can be lacquered and vacuum metallized.
Joining
1. Welding Molded PEK and PEEK can be joined by ultrasonic and friction welding. The high melting temperature (334°C) and high contact pressure must be taken into account.
2. Bonding The surfaces to be joined must be clean, dry and free from grease. The strength of the join can be improved by roughening, flame treatment or etching with chrome sulfuric acid. Suitable adhesives are epoxide resins, cyanoacrylate, anaerobic and silicone adhesives. EP resins result in the greatest strength.
PROPERTIES
1. Inert polymer, having very high heat stability
2. Very high melting temperature (335 ºC)
3. Excellent chemical resistance
4. Excellent tribiological properties
5. Very strong and rigid
6. Excellent fatigue resistance
7. Exhibits good load bearing properties
8. Excellent creep resistance
9. Excellent flammability rating and low emission of smoke and toxic gases during combustion
10. Very good electrical properties over a wide range of temperature
APPLICATIONS
Typical Applications
Automotive, aircraft and electrical industry in the form of injection moldings, cable sheathing, monofilaments and film.
Metal parts are coated electrostatically or by fluidized bed. Trials are being undertaken in hip joint replacement.
Aerospace
Glass/carbon fibre reinforced composites for aerospace components, missile connectors and radors.
Automotive
Cages, gear support bearings, clutch seals, transmission parts, rollers, gears, guides.
APC (aromatic polymer composite) from ICI, a combination of PEEK as matrix and C-fibers as reinforcement is supplied as tape (3mm to 500mm wide) and sheet which can be used in high performance applications. The excellent mechanical properties are achieved by special pretreatment of the C-fibers.
Claimed advantages are:
- 30% lighter than aluminum,
- more easily processed than EP resins,
higher impact strength than unreinforced PEEK and no propagation of cracks,
high shear & fatigue strength,
- low water absorption and high resistance to solvents,
- scrap can be recycled,
- can be thermoformed, cold rolled and wound.
No comments:
Post a Comment