Controlling the Curing and the Post-Curing State of Polysiloxane Coatings for Release Liners Application

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Title: Controlling the Curing and the Post-Curing State of Polysiloxane Coatings for Release Liners Application
Authors: Casallas Cruz, Xihomara Lizzet
Thesis advisor: Prof. Dr. Uwe Beginn
Thesis referee: Prof. Dr. Markus Haase
Abstract: Silicone release liners are silicone coatings on top of papers or films that are used in the adhesives industry to prevent adhesion before the final use of the adhesive e.g. labels. The process of production of release liners involves the casting of molten polysiloxanes on top of the substrates that crosslink by hydrosilylation reaction forming silicone networks. The quality of the release liner can be assessed by diverse methods usually performed when the coating process has been finished. Rarely an online control of the reaction is possible. Fluorescence spectroscopy was found to be a non-invasive useful method to control the reaction during the whole process by introducing very small concentration of fluorescent molecules in the polymer formulations; those fluorophores are sensitive to environmental changes as the silicone polymer molecules crosslink. In response to that stimulus, the fluorescence intensity varies along the time upon reaction allowing the identification of the gel point and further modifications or molecules rearrangements in a post-curing stage within weeks that are non-observable with conventional quality control methods. It was found that the fluorescent molecules do not require to be attached covalently to the polysiloxanes, thus fluorescence spectroscopy is a simple method to implement for controlling the production of silicone coatings. Moreover, the characterization of several silicone formulations was performed to find the optimal conditions for the production of release liners and to understand the effect of every component in the formulation on the performance of the silicones. The kinetics of the reaction was also studied and even a mechanism for the hydrosilylation reaction was proposed.
Subject Keywords: release coatings; Polydimethylsiloxane; Hydrosilylation; Fluorescence; Crosslinking; Gelation; Covalent-Labelling; Silicone; Release-liners; non-covalent-labelling
Issue Date: 19-Nov-2019
Type of publication: Dissertation oder Habilitation [doctoralThesis]
Appears in Collections:FB05 - E-Dissertationen

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