Lanxess : Polyamide 6 and 66 grades withstand temperatures of up to 200 °C

Cologne - Specialty chemicals company LANXESS has developed a further high-tech heat stabilizing system for Durethan polyamides - XTS3 (Xtreme Temperature Stabilization). It is aimed primarily at applications in the electrical and electronics sectors and under the hood, particularly in the oil circulation system.

As with the XTS1 system already launched on the market by LANXESS, it raises the continuous service temperatures that polyamides 6 and 66 can withstand by around 60 °C to approximately 200 °C. Yet its heat stabilization properties are based not on an inorganic but on an organic additive system that is metal- and halide-free. 'The material grades of Durethan incorporating this stabilizer system are ideal for manufacturing plastic parts that are subjected to high thermal loads and come into direct contact with metal components. The metal- and salt-free stabilization ensures there is no contact corrosion,' explains Thomas Linder, expert in Durethan product and applications development at LANXESS High Performance Materials business unit.

Alternative to specialty thermoplastics

The first materials with the new stabilization are two polyamide 6 and 66 grades reinforced with 30 percent short glass fibers that will be marketed in the future under the names Durethan BKV 30 XTS3 and AKV 30 XTS3. Potential applications in the engine compartment include oil filter housings, oil pans, housings of transmission control systems and sensors that come into contact with oil, while those in the electrical/electronics sectors include plug connectors, plug strips and housing parts. 'As well as their long-term thermal stability, both compounds offer an excellent price-performance ratio and high processing stability. In many applications, they could be an alternative to costly heat-stabilized specialty thermoplastics such as polyphenylene sulfide, semi-aromatic polyamides and polyamide 46,' explains Linder.

Tensile stress at break still high after hot-air storage

The long-term stability and low tendency to become brittle under high thermal stresses can be seen for both polyamides in hot-air aging tests, for example. Even after 2,000 hours of storage at 200 °C, the reduction in tensile stress at break is not measurable for the polyamide 6 grade and is only 15 percent for the polyamide 66 grade. Under these conditions, strain at break is still above 2 percent (polyamide 6) and 1.8 percent (polyamide 66). By way of comparison, the tensile stress at break of comparable polyamide 6 grades with copper-free heat stabilization that is typical of the market drops to around 50 percent under the same conditions. In the case of corresponding polyamide 66 grades, a decline in tensile stress at break to 50 percent of the initial value is observed after just 1,000 hours.

Easy flowing, stable process

The two new polyamides are easy to process in a single robust production process. The processing range is comparatively wide, with hardly any susceptibility to moisture, and is similar to that of established standard Durethan grades. The high flowability of the two polyamides deserves special notice. 'It opens up greater processing flexibility for injection molders. For example, production can be carried out at lower temperatures and thus cycle times and energy costs can be cut. Alternatively, with the same injection pressures, molders can achieve longer flow paths compared to similar standard polyamides, which enables the use of simpler molds, for instance,' explains Linder. The mechanical properties of the two polyamides remain largely unaffected by heat stabilization. They are at the high level that is characteristic of H3.0 grades of Durethan with 'classic' organic temperature stabilization.