Processors of multilayer blown film know it is critical to keep precise control of the thickness of the various layers of a film's structure, especially the costly barrier-material layers. A new measuring system is claimed to enable processors to measure these layers during processing, at output rates up to 450 m/min. 

The new system was developed by researchers at two German institutes, the IKV (Institute for Plastics Processing) and the Fraunhofer Institute for Laser Technology, both based in Aachen. Measuring the layers in multilayered film, during blown-film extrusion, has not been possible—or at least not with any great degree of accuracy—with barrier layers in these structures often as thin as 1-20 µm. The barrier needs to be guaranteed over the entire web surface, which means processors often are pushed to use more of the barrier material—EVOH, for instance—than may actually be necessary. With this new thickness gauge, it could be that processors can save significant amounts of material.  

The system developed is said to be able to measure each of the layers in a film, and document this in real time during blown-film extrusion. The measurement system relies on an interferometric sensor and infrared light to detect changes in the refraction index of the film. These variations can be tracked on the film's surface as well as where two layers meet.

Working with the two institutes are four German SMEs (small-to-mid-sized enterprises) including processor A+C-Plastic Kunststoff GmbH in Eschweiler, which has been running the system on one of its production lines for some months. Other companies involved in the development were Octagon GmbH and Elovis GmbH, which both manufacture measuring equipment, and extrusion line manufacturer Kuhne, which tested the system in near-production conditions before A+C put it to the real-world test.

Processors interested in learning more should make plans to attend the K 2010 tradeshow this fall in Düsseldorf, Germany, where the IKV will present the film inspection system at its stand (14/C16).