Einfluss der Verfahrensparameter auf Gaseinschlüsse in kalandrierten Kautschukbahnen (English shop)

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Calenders are frequently used in the rubber and plastics industry for forming polymer melts into sheets, films and continuous webs. The plastic or rubber products produced in this way exhibit very narrow thickness and width tolerances as well as a very high surface quality. Despite the high precision of calender lines, material defects in the form of gas inclusions within the calendered webs cannot be avoided.

In the present work, the relationship between the velocity field in the calender nip and the occurrence of gas inclusions in the calendered webs, as well as the movement of gas bubbles in the rolling bank of the feed zone of the calender nip, are visualised. For this purpose, the flow properties of the rubber compound, the pressure field in the calender nip as a function of the feeding method, and the process parameters roll circumferential speed, roll temperature, nip height, friction and positioning of the wedge, taking into account the height of the rolling bank, are varied. The rheological properties of the rubber compounds are influenced by the addition of recycled rubber particles. The number, the size of the cross-sectional area, the position and the shape of the gas inclusions in the calendered rubber webs are measured by means of digital radiography. This makes it possible to visualise the gas enclosed in the material along the entire calender line. The velocity fields in the calender nip are visualised using a two-coloured compound. Conclusions about the movement of gas inclusions in the rolling bank are drawn from the movement of polystyrene spheres and glass spheres. The measurement is carried out by means of X-ray tomography.