Injection-moulded parts High surface quality, low warpage: Transmission oil pans made from polyamide 6

Editor: Alexander Stark

Germany — Polyamide 66 has been widely used for transmission oil pans in cars. But polyamide 6 offers some advantages over its brother. It fulfills the key requirements regarding thermal and oil resistance, toughness and surface quality and is much cheaper than any comparable polyamide 66.

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Lanxess experts inspect the high surface quality of the transmission oil pan.
Lanxess experts inspect the high surface quality of the transmission oil pan.
(Source: Lanxess)

In the manufacture of transmission oil pans, polyamides offer numerous advantages over sheet steel or die-cast aluminum in terms of lightweight construction, cost-cutting functional integration and design flexibility. Polyamide 66 in particular has therefore found widespread use in series production of these large injection-moulded parts in recent years. However, polyamide 6 is also very well suited to the purpose, as is evident from an increasing number of applications. One recent example of this trend comes in the form of a transmission oil pan made by IBS Filtran and consisting of Durethan BKV35H2.0 from Lanxess. It is part of latest-generation automatic transmissions for vehicles from various carmakers. The company has extensively investigated the oil and thermal resistance of the polyamide 6 reinforced with 35 % by weight of short glass fibers.

Endurance tests at 150 °C in various transmission oils have shown that in terms of aging, there is no difference from a comparable polyamide 66. In fact, polyamide 6 has somewhat better impact resistance and elongation at break, which means that the oil pan is generally better able to cope with stone chippings. The excellent surface quality that can be achieved with the compound is another benefit. These surface characteristics in the area around the oil pan gasket, for example, help the gasket to work well. Polyamide 6 also exhibits less shrinkage, which has a similar effect because it results in less warpage. The material's good weldability is another of its strengths. The inner shell of the oil filter is joined to the main body of the pan by means of vibration welding.

Structural supply problem for polyamide 66

Over the last three years, polyamide 66 has at times become much more expensive mainly due to shortages of adiponitrile, a primary product for the manufacture of the material, and is in some cases not available in sufficient quantities. This has also prompted manufacturers of plastic components for oil circuits to seek more affordable and reliably available alternatives to polyamide 66. Polyamide 6 is a viable candidate thanks to its similar profile of properties. “For instance, in addition to car transmission oil pans, we are increasingly seeing truck oil pans and cylinder head covers made from polyamide 6 being used in series production and development,” explains Babak Talebloo, key account manager for IBS Filtran at Lanxess.

The company is expanding its range of polyamides for vehicle oil circuits continuously. Among the new additions are Durethan ECOBKV30H2.0, ECOBKV35H2.0 and ECOBKV60XF. Recycled fibers manufactured from waste glass make up 30 %, 35 % and 60 % by weight respectively of these three polyamide 6 compounds. ecocycle, an independent inspection company, has examined the amount of recycled material in each compound using the mass balance method and awarded an ecoloop certificate in accordance with ISO 14021:2016.”Another example of new applications in the oil circuit comes in the form of the polyamides of the XTS series. XTS stands for Xtreme Temperature Stabilization and underlines the compounds' extraordinarily high long-term thermal resistance of up to 230 °C. They can be used for oil pans on vehicles that have the catalytic converter mounted near the transmission, which results in the oil pans being subjected to increased thermal loads during exhaust treatment intervals. According to the company, the use of these compounds can avert the need to install deflector plates to protect the oil pans from intense heat.

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