In car headlight production, adhesive bonding of the polycarbonate lenses with their polypropylene housings must satisfy highest demands on sealing. Even the tiniest leaks would lead to penetration of humidity and consequently to impairment of the headlight lens with the result that the light radiation angle would in turn be negatively affected.

HELLA Australia pty Ltd, a fully owned subsidiary of HELLA GmbH & Co. KGaA Germany, was started 50 years ago as the first operating overseas HELLA plant. Here the grooves of the PP housings are cleaned and activated with Openair-Plasma^® through rotary jets before applying a 2K-silicone adhesive. During this operation, the surface energy of the PP rises from 35Jm/m² to over 72mJ/m². The thereby increased adhesion properties of the subsequent bonded joint provide for its full sealing. The rotating feature of the plasma jets of type RD1004 ensures that not only the bottom of the PP groove but also its side walls are activated at the same time. This process, which is patented worldwide by Plasmatreat, has a particularly gentle effect on the material to be treated since it distributes the plasma, in a scattering manner, in a circular path rather than providing for a high pointwise energy input. 

Apart from that, David Byrne, Chief Assembly Engineer at HELLA Australia Pty Ltd, especially appreciates the high degree of process safety and reproducibility offered by the Plasmatreat generator FG5002S: "The generator is equipped with a PLC controller with touch screen for a precise display of operating and error messages. What is of paramount importance to us is the signal linkage with the lower- and higher-level control systems." All monitoring functions and their readings such as current, voltage, frequency, number of revolutions, plasma intensity, fiber optic detection and others can be transferred via the addition of the fieldbus interface to HELLA's own higher-level cell control system.

Benefits
Openair-Plasma^® offers the user the following benefits:

• Activation of even complex geometries
• High adhesion properties when bonding PP with PC
• Gentle pretreatment through the use of rotary jets
• Extraordinarily high degree of process safety and process reproducibility
• Distinct quality increase in production

Headlights