Highly filled silicone for sealing headlights

Endurance testing proves resistance to wear of ViscoTec stators
Abb. 3: Statorgeometrie (PresseBox) (Töging a. Inn, ) A variety of dosing processes can be used in the manufacture of LEDs in the automotive sector. Alongside conventional potting of the LED chip, typical areas of application include the application of heat transfer paste for selective heat dissipation and the use of adhesives to join components.

Modern LEDs are high-performance products which, as a consequence of the energy density of the light, ask a great deal of the materials used. Organic plastics quickly reach breaking point in this field and material manufacturers are focussing their attention on new types of plastic. The aim is to combine as many different properties as possible in a single medium. In the case of LED production, for example, light stability, temperature resistance, UV stability, resistance to ageing and high adhesion are of crucial importance.

Manufacturers tend to use what is known as “additivation” – adding fillers with specific characteristics – to achieve this versatility of material properties. In the medium itself, these fillers often increase density and result in high material aggressiveness towards the dosing components. The eccentric worm pump by ViscoTec has already proved its compatibility for use with abrasive media in numerous applications and is now doing it again: endurance testing carried out in our in-house laboratory tested the resistance to wear of the stator first in 180,000 cycles of quantity dosing and then in continuous operation. The test medium – an RTV silicone filled with aluminium oxide – was taken from a drum and fed into the 4RD6-H EC dispenser from the ViscoTec RD series. In keeping with the requirement from the automotive industry, a dot-dosing application with 0.027 ml per dose was simulated for sealing headlights. Three times a day, temperature and pressure values were recorded at the pump outlet and doses were evaluated. The parameters recorded were highly consistent and there was no indication of wear.

Computer tomography was applied in quality assurance to measure and evaluate the stator geometry before and after endurance testing. There was no visual or dimensional evidence to suggest defects. The ViscoTec dispenser was thus deemed suitable for this application.

Fluids enhanced with additives have been in use in dosing applications in automated settings for many years, and the trend is on the increase. The abrasiveness of the media used, which is often a consequence of additivation, is forcing the manufacturers of dosing technology and equipment to confront the subject of wear and the factors that influence it. ViscoTec is determined to face up to this challenge, turning its many years of experience to its advantage in doing so. The long product life of ViscoTec stators is the result of continuous optimisation of the elastomer compounds. For customers this means fewer failures, minimum maintenance overheads and more effective automated production lines.

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ViscoTec Pumpen- u. Dosiertechnik GmbH
Amperstraße 13
D-84513 Töging a. Inn
Elisabeth Lenz
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