Hydrolysis‑Resistant, Laser‑Transparent PBT Delivers Superior Performance in Automotive Engine Actuators

Not all polybutylene terephthalate (PBT) grades perform equally in demanding automotive applications. In particular, actuators that control combustion‑process swirl and air‑turbulence in diesel engines demand exceptional dimensional stability and resistance to hydrolysis in hot, humid engine compartments.

Lanxess’s specialty PBT, selected by a German automotive manufacturer for a new diesel‑engine line, meets these criteria. The compound’s hydrolysis‑stabilized formulation ensures long‑term reliability, while its laser‑transparent properties enable laser‑transmission welding—an increasingly popular, clean, and high‑strength joining method for plastic housings.

Achieving both hydrolysis resistance and laser transparency is a material‑design challenge. "Pocan B3233HRLT is a unique solution that satisfies this dual requirement," notes Jean‑Marie Olivé, application‑development expert at Lanxess High‑Performance Materials. The actuators are engineered and manufactured by Sogefi Air & Cooling SAS in Orbey, France, part of the Sogefi S.p.A. group—a global leader in vehicle filter systems and engine‑cooling solutions.

Alternative materials—such as 30 % glass‑reinforced nylon 6 or non‑laser‑transmissive (LT) 30 % glass‑reinforced PBT—were considered. However, nylon’s moisture absorption reduces dimensional stability, and LT PBT would require older joining techniques (e.g., screwing or ultrasonic welding) that produce weaker seams and lint.

Laser‑transmission welding excels for small, complex components, especially as automotive electronics miniaturize. The process directs a laser beam through a transparent part, where it is absorbed by a second, black‑pigmented component, generating heat that melts and bonds the two parts. In the actuator, the transparent half is fabricated from Pocan B3233HRLT with a laser‑transparent black finish, while the housing half uses Pocan B3233HR.

The compound’s durability under extreme conditions is validated by the SAE/USCAR‑2 Rev. 6 long‑term test—a rigorous evaluation of hydrolysis stability involving repeated temperature cycles at up to 100 % relative humidity. Specimen testing confirms Class 3 performance, withstanding temperatures up to 125 °C (257 °F).

These attributes make Pocan B3233HRLT an ideal material for next‑generation automotive actuators that demand both resilience in harsh engine environments and the precision of laser‑based manufacturing.