Specialty chemicals company LANXESS has developed a new heat stabilization system called XTS2 (Xtreme Temperature Stabilization) for polyamide 66 variants of Durethan. This system increases the heat aging durability of the polyamides so much that they reach into the heat deflection temperature range. “Thanks to the new iron-free thermostabilization, our polyamide 66 variants can withstand temperatures of up 230 °C in the long-term. They therefore provide an alternative to costly heat stabilized specialty thermoplastics, such as fully or semi-aromatic polyamides and polyphenylene sulfide,” explains Dr. Thomas Linder, a Durethan material development expert in the High Performance Materials business unit at LANXESS. The first product from the XTS2 product range is a polyamide 66 reinforced with 35 percent glass fibers (by weight), which will be marketed as Durethan AKV35XTS2. There are also plans to offer XTS2 product variants with higher and lower glass fiber contents. A blow-moldable polyamide 66 for turbo charger components of cars that is stabilized with the XTS2 system is also in development.

Good flow characteristics and high surface quality

Compared to Durethan-brand polyamide 66 variants with the same glass fiber content containing H2.0 thermostabilization, Durethan AKV35XTS2 exhibits better flow characteristics. As Linder points out: “This makes it easier to realize delicate component geometries and thin walls.” Another advantage is the high surface quality, which is even better than similar material grades with XTS1 heat stabilization.

LANXESS extensively tested the high long-term temperature resistance of the new polyamide 66 by conducting hot air aging tests. “Even after 3,000 hours of storage at 230 °C, the reduction in tensile stress at break and elastic modulus is barely measurable, meaning the material maintains its initial strength and stiffness despite the high thermal load,” says Linder. The material was mainly designed for high-tech engine applications that are exposed to unusually high temperatures – such as air intake manifolds with integrated charge air coolers or air pipes located in the vicinity of the turbocharger.

Precisely tailored thermostabilizations

For thermostabilization of Durethan compounds LANXESS already uses miscellaneous additive systems that are tailored to various heat resistance levels, e.g. to those of components under the hood. For example, the established XTS1 and XTS3 systems enable continuous use of Durethan at around 200 °C. Just as H3.0 thermostabilization, XTS3 benefits from a very low metal and halide content. “They are especially suitable for plastic components that come into direct contact with metal components. This is because the metal- and salt-free stabilization helps to prevent contact corrosion,” explains Linder. Typical applications include housing parts, plug connectors and connector strips. By contrast, the XTS1 and, for example, the H2.0 system are intended for black components where contact corrosion is not an issue.