Möhle-Saul, Sunna (2024)
Thermal Switching of the Opacity of Polymer Films for the Use in Thermo-Responsive Papers.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00027752
Dissertation, Erstveröffentlichung, Verlagsversion

Kurzbeschreibung (Abstract)

Thermal papers have become an integral part of everyday life: they are used in cash register receipts, parcel labels and admission tickets. Wherever information needs to be recorded quickly, cheaply and for a limited period of time. However, traditional thermal papers are subject to criticism because their color developer systems can contain substances that are potentially harmful to health and the environment.Therefore, there are already alternative papers based not on the chemical development of color, but on the physical effect of switching a highly light-scattering structure from opaque to transparent. The goal of this work is to find another alternative for an opaque-transparent film applied to paper that can be thermally switched. For this purpose, systems of crystalline low molecular weight substances in polymer matrices are investigated. The components are formulated in different configurations and coated onto substrates. The thermal switchability in the opacity of the resulting films is determined by measuring the optical density before and after thermal switching. Natural waxes such as fatty acids and tristearin and synthetic waxes as well as binary organic eutectic mixtures are investigated as low molecular weight crystalline substances. By measuring the scattering parameters, it is determined whether mixtures in a eutectic composition have a higher scattering effect than their non-eutectic compositions. In the course of the work, promising systems are identified that can serve as basis for possible thermally switchable coatings.

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