Finding openings for polyketone compounds

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With Akrotek PK semi-crystalline aliphatic polyketone compounds, Niederzissen, Germany-based compounder Akro-Plastic now fills a gap left by Shell Chemicals when it discontinued its Carilon polyketone engineering plastic in 2000, a product first launched in the US in 1996. Shell Chemicals gave its polyketone patent rights in 2000 to US company SRI International in Menlo Park, California.

Akro-Plastic has teamed up with South Korean company Hyosung, whose R&D department developed a “Karilon” polyketone polymer in 2003 as a SRI International sub-licensee. Hyosung commenced production in 2012 with 1,000 tpa “semiĆ¢€'continuous” polymerisation capacity in Ulsan, it said when announcing commercialisation in November 2013.

Hyosung’s polyketone production capacity is planned to rise to 50,000 tpa of continuous polymerisation capacity in the second quarter of 2015 and to be expanded to 200,000 tpa by 2020, Akro-Plastic innovation manager Thilo Stier told EPN at the VDI plastics in automotive engineering conference in Mannheim, Germany in March.

Stier revealed Akro-Plastic had received its first 5 tonnes order for compound produced in Niederzissen, from one of three processors known to have bought enough Carilon while it was still available to keep producing until today.

In contrast with Shell’s strategy, “Hyosung says it only wants to sell polyketone polymer to compounders such as AkroĆ¢€'Plastic. This is now a better situation than earlier for end customers – it means more competition”, Stier suggested. As an example, Schulman introduced Schulaketon polyketone compounds at K 2013.

The Akrotek PK range consists of three PK-HM, PK-TM and PV-VM unreinforced grades; 15%, 30% (3 types), 50% and 60% glass fibre reinforced grades; and a 12% carbon fibre reinforced PK-HM CF12 grade. Stier said Akro-Plastic is working on blends, as well as grades for defined friction and wear properties. This includes Akrotek PK-HM TM (tribologically modified), with almost half the specific wear rate of a typical POM copolymer. Öchsler already uses polyketone to mould gears.

Polyketone polymer is easily synthesized, as a copolymer for spun fibres from ethylene and carbon monoxide in the presence of a palladium catalyst, and as a terpolymer for extrusion and injection moulding with addition of propylene.

Using low-cost monomer and CO enables polyketone grades with PA12 type properties at PA66 price levels. Polymerisation cost will be much lower when continuous compounding starts.

Stier says polyketone has good green credentials, due to more than 50% carbon monoxide content.

In extrusion, R"chling Sustaplast announced in June new Sustakon ram extruded polyketone semiĆ¢€'finished items with resistance to permanent high dynamic load. A 150µm Akrotek PK-HM film made on a cast film extrusion line by Lite in Gaflenz, Austria provides a low friction film with barrier properties similar to, or the same as, EVOH barrier layers, along with high chemical resistance.

Akro-Plastic highlighted another application: a single-layer 8mm outer diameter, 1mm wall thickness, polyketone fuel line, which has higher fuel barrier than a multilayer PA12/PVDF line. A fuel line quick connector in 30% glass fibre reinforced polyketone is claimed as “achieving significantly better barrier” than a PA12 GF30 equivalent and to be at least 40% less expensive.

Akrotek PK has shown high chemical resistance with 30 days exposure to 10% HCl, 30% H2S04 or “battery acid” (38% H2S04) with just surface discoloration and elongation at break hardly changed. In the same test, long-chain PA12 was severely attacked and short-chain PA66 destroyed after 48 hours. High hydrolysis resistance ensures Akrotek PK compliance with Volkswagen’s TL 52682, 1000h, 135°C, 50% glycol/water (G13) coolant test.

Akro-Plastic points out, however, that radiator tanks in VW-approved PA66 GF30HR tend to show washing out of glass fibres with time, and it claims this cannot happen with Akrotek PK, as “it is not dissolved by the G13 glycol/water mixture”. 

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