HNBR-coated rollers in the hold of transporter planes
Made with Therban®
Roller conveyors are used to push freight into position. The rollers on the containers must be able to withstand rapid fluctuations from one temperature extreme to the other. This is why the Mitex rubber factory in Erkrath has chosen Therban® as the coating for the rollers used in the holds of transporter planes.
HNBR elastomers such as the rubber
Therban® made by LANXESS are increasingly proving their worth in applications where standard rubber blends aren't up to the job. Indeed, Therban is about to take to the skies: the Mitex Gummifabrik Hans Knott GmbH, based in Erkrath, has been supplying a renowned aeronautical company with Therban-coated rollers for airplane holds since 2000. In this application it is above all the high abrasion resistance and mechanical strength of this material, as well as the constancy of its physical properties under extreme temperature and climate fluctuations, that are in demand.
To facilitate handling of bulky freight containers, the floors of airplane holds are often fitted with roller conveyors so that freight can be pushed into position. These conveyors have to function under difficult circumstances since the ambient conditions in the hold are often extreme. Soon after take-off, for example, it becomes exceedingly cold - up above the clouds the temperature can dip to an icy -40°C, which soon removes any moisture from the air in holds that frequently lack insulation. After landing, the climate can quickly switch to the other extreme - internal temperatures of up to +50°C are an everyday occurrence.
These wide temperature fluctuations from take-off to landing pose major challenges for the elastomer materials used to coat the rollers - it is not surprising that heavy-duty steel is also used for this task. As Georg Heinen, Managing Director of Mitex explains: "These rollers have to be able to withstand contact with oil, water and contaminants. Above all, however, they must be able to cope with the rapid change from extreme heat to extreme cold and the fluctuating climatic conditions in the hold, without becoming brittle, without breaking down as a result of the internal build-up of heat under maximum stress and without aging prematurely. At the same time, their property profile has to remain as constant as possible, whilst adhering to the particularly stringent quality guidelines in force in the aeronautical industry."
After all, freight stored in the hold is not up in the clouds for ever. When things have to move quickly, the process of loading and unloading transport containers, that weigh several tons, can get fast and furious. And it goes without saying that the rollers must not become "flat-footed" when subjected to permanent loads - a problem that would make the difficult maneuvers in the confines of the hold even more complicated. Additionally, the rollers must be able to withstand sharp-edged metal items and maintain their rough surface to stop the containers from slipping. A high level of hardness beyond Shore A, low compression set, high tear resistance and high abrasion resistance are further criteria with which the elastomer rollers must conform. To achieve this profile, the engineers at Mitex experimented with various different materials for the coating on the approx. 10 cm-thick and equally wide rollers, including polyurethanes, NR, EPDM and NBR. "Yet we soon hit on Therban®," recounts Heinen. "With natural rubber the build-up of heat was too great as a result of the permanent flexing work, whilst EPDM roller coatings became smooth too quickly. Using Therban®, on the other hand, we were able to meet every single one of the requirements and gain the upper hand over our rivals worldwide."
The robust rollers are just the latest application where Therban® is being used under extreme conditions. Further examples from related areas include hard HNBR rollers used in cold rolling mills in the production of sheet steel at temperatures of up to 160°C. And the material also excels in rollers for the production of chipboard and for timber lamination, as well as in paper production, thanks to its exceptional compressive strength. Meanwhile, in textile and yarn production, Therban® roller coatings have proved their worth thanks to their excellent tear resistance.
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