#1154
Author: Charles A. Bishop, C.A.Bishop Consulting Ltd.
Email: cabuk1@freenetname.co.uk
Subject: Different roll could be expected to give different temperature performance because of the amount of absorbed water in the film.
Different roll could be expected to give different temperature performance because of the amount of absorbed water in the film. I am assuming the tensions are also held constant as well as the deposition drum temperature. The absorbed water can outgas from the back surface of the polymer whilst in contact with the drum and can affect the heat transfer coefficient. The higher the gas load between the film and the drum the higher the heat transfer coefficient and hence the lower the expected temperature of the film. So changing polymer or supplier of the 'same' polymer can lead to differences in performance. It is possible to inject gas between the web and the drum to increase the heat transfer coefficient. Using this technique it may also standardise the heat transfer coefficient and make the temperature rise more predictable. For more details of this process see US Patent No.5076203
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