line of polybutylene terephthalates (PBT) and polyamides (PA)
Custom-tailored mechanical properties, easy to coat
LANXESS sees great potential for the use of PBT and
polyamide compounds in production of vehicle exterior body parts -
for example bumpers, sills, front grilles, door handles, fuel tank flaps,
spoilers and mirror housings. "That is why we are building up a wide
range of Durethan and Pocan materials for this use segment. The
development work is focusing on application-specific, optimized
mechanical properties, as well as good surface qualities and good
paintability," says Frank Krause, design expert at LANXESS.
New PBT for fuel tank flaps — suitable for CDC and
An innovative material for fuel tank flaps, for example, is
Pocan B 5220 XF reinforced with a glass bead content of 20 percent.
The product is an alternative to blends of polyphenylene ethers and
polyamide (PPE+PA), which are often used in series-produced fuel
tank flaps because they can be painted online. A disadvantage of
such blends, however, is their high degree of moisture absorption,
which has an undesirable effect on the required dimensional
accuracy. PBT, by contrast, stands out by virtue of its high degree of
dimensional stability. "Our Pocan B 5220 XF also withstands the
usual temperatures required for cathodic dip coating (CDC). That
means the part can be mounted to the vehicle body and go through
online coating and the CDC process along with it, which yields
savings on logistics and coating costs," adds Krause. Mineral-filled
PBT and PA compounds, on the other hand, which fuel tank flaps are
also made of, are not suitable for CDC.
LANXESS has intensively studied the new material's thermal
expansion behavior, using fuel tank flaps that were produced on a series-production tool. "Even after one hour at 200 °C the expansion of
the freely suspended parts was negligible," says Krause. Another
strength of the new PBT is the good surface quality and paintability,
which is due to the absence of glass fibers in the material. Compared
to similar glass bead-reinforced standard materials, its much
improved melt flow properties and the approximately 50 percent
greater toughness are especially noteworthy.
New (PC+PBT) blend for radiator grilles
LANXESS specially developed Pocan TP 406-001 for radiator grilles.
"The non-reinforced polycarbonate+PBT blend material was
conceived primarily for parts with Class A surfaces, which are given a
high-gloss coating," Krause says. The material displays very low and
uniform shrinkage and hardly any tendency to distortion at all. Thanks
to the blend's extreme toughness even in cold temperatures, the
radiator grille does not shatter into shards in the event of a collision,
which helps protect nearby pedestrians. The high heat deflection
temperature ensures that long, horizontal grille fins do not sag as a
result of exposure to the radiator heat.