Polyketone High-Performance Thermoplastic Polymer
Aliphatic Polyketone (PK) is a high-performance thermoplastic polymer with a melting point of 220°C. This is the result of polar ketone groups in the polymer backbone creating a strong attraction between polymer chains. Polyketone (PK) meets the demands of a wide range of applications and has been enjoying somewhat of a renaissance thanks to its environmental credentials relative to other polymers. This is due to comonomer CO (carbon monoxide) in the structure of the polyketone. An industrial “waste” gas which can contribute to global warming, it bonds with a polymer to form a highly favourable monomer.
Polyketone has several properties which no other polymer has in this combination. Freshly injection-moulded polyketone has the greatest yield strain (over 20 %) compared to all other semi-crystalline polymers, virtually independently of moisture. This tremendous elasticity gives many components made of PK a high degree of safety in the design phase.
The outstanding characteristics of PK:
• excellent resilience
• reduced moisture absorbtion
• good tribological properties
• good resistance to chemicals
• good hydrolysis resistance
• shorter cycle times
Freshly injection-moulded polyketone has the greatest yield strain (over 20 %) compared with all other semi-crystalline polymers, virtually independently of moisture. This tremendous elasticity gives many components made of AKROTEK® PK a high degree of safety in the design phase.
AKROTEK® PK is particularly well suited for designs which must exhibit constant mechanics even under changing climatic conditions.
Polyketone has an inherently low moisture absorption. Tests according to ISO 1110 show that all tested AKROTEK® PK compounds reach their equilibrium moisture after just 2 to 3 days, compared with polyamide 6.6 compounds, which require over 20 days.
Moisture absorption vs. Exposure time 500 h at 70 °C and 62 % rel. humidity following ISO 1110.
The measured dynamic friction coefficient and specific wear rate show outstanding values with even the standard AKROTEK® PK grades. Our TM (tribologically modified) grades can significantly reduce both wear and the dynamic glide coefficient.
Universal Tribometer Set-Up
Pin-Plate Principle: We have tested the tribological properties of various AKROTEK® PK grades using a universal tribometer according to the “pin-plate principle”. With this method, a sample taken from a tension test bar is pressed against an oscillating steel plate (100Cr6).
The Least Wear
It may not be possible for design reasons to avoid pairings of similar friction surfaces, AKROTEK® PK shows the least wear of all polymers tested. When different materials are used, a combination with PA is good, and a combination with POM is the best pairing by far.
Laser welding is also a contact-free welding system that is used for very narrow tolerances of the components to be joined. The shear forces measured on components overlapping with diode-laser-welded components exhibit the same level for both AKROTEK® PK-HM and AKROTEK® PK-VM GF 30, but less than AKROMID® B3 GF 30.
Infrared welding is a contact-free welding method in which the components are warmed with an infrared radiator and then welded under joining pressure. In the infrared welding method, AKROTEK® PK-HM demonstrates welding seam resistances of over 90 % of the initial stability. This extremely high figure enables welded designs with virtually no mechanical weakness in the seam area. The strength of AKROTEK® PK-HM GF 30 is almost at the same level as dry AKROMID® B3 GF 30. Thus nearly 90% of the polymer strength is achieved with glass fibre reinforced polyketone.
Typical Infrared Welding parameters are:
- Cooling-time: 40 seconds
- Warm-up distance: 18,5 mm
- Warm-up time: 20-30 seconds
- Power: 700W – short wave
- Joining pressure: 2-5 N/mm²
Resistance to Media
Further information on the media resistance of AKROTEK® PK can be found on the right link.
The minimal loss of tensile strength in the samples exposed to ethanol, methanol or mixtures of the two materials results from the plasticising effect of alcohol. The tensile strength can be restored by drying the samples before testing.
Resistance to Media
The chemical resistance of AKROTEK® PK is one of the materials’ biggest strengths. It resists corrosion due to weak acids, which typically corrode longchain polyamides such as PA 12 and PA 6.6. Only light surface discolorations can be observed after 30-day conditioning in 10 % hydrochloric acid, 30 % sulphuric acid or battery acid. The elongation at break remains virtually at the starting level, however.
Resistance to Media
Due to the excellent hydrolysis resistance of AKROTEK® PK, only a brown discoloration on the polymer appears after ageing as per the VW standard (TL 52682) for over 1,000 h/135 °C, compared to a polyamide 6.6 GF 30 HR, as used today as the standard for water tank applications.
An aged component from this standard generally exhibits fullblown glass fibres. This is not the case with AKROTEK® PK-VM GF 30, since the polymer is not dissolved by the glycol (G13)/water mixture.
AKROTEK® PK is an absolutely versatile material. The most important markets for AKROTEK® PK are the automotive, furniture and food industry and mechanical engineering. Have a look at the polyketone with universal qualifications and its applications.
The replacement of metals by engineering plastics in the drinking water and food sectors has risen steadily. A wide variety of applications are already made of plastics, such as fittings, water meter housings, filter housings and seals. Reade more here.
Disclaimer: All specifications and information given on this website are based on our current knowledge and experience. A legally binding promise of certain characteristics or suitability for a concrete individual case cannot be derived from this information. The information supplied here is not intended to release processors and users from the responsibility of carrying out their own tests and inspections in each concrete individual case. AKROMID®, AKROLEN®, AKROLOY®, AKROTEK®, ICX®, PRECITE® and DIA(hr)LOG® are registered trademarks of AKRO-PLASTIC GmbH.