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Gelierungs- und Intumeszenzmechanismen von Aluminiumphosphat-Hydrogelen
Fire-resistant glazing consists of a pane composite with hydrogel fillings. These hydrogel layers place particularly high demands on the manufacturing process and the formation of a heat-blocking foam after intumescence in the event of fire. The hydrogels used today are mostly based on polymers or water glass systems and have limited temperature resistance, which is why new hydrogel fillings are being sought. Systems based on aluminium phosphate (Al(H2PO4)3 + monoethanolamine (MEA) + boric acid) are promising candidates. However, these systems lack fundamental understanding of the mechanism involved in the preparation process (gelation) and in the intumescence of the hydrogel. In this work, various characterization methods are used to elucidate the structural composition and temperature-induced changes during the foaming of aluminium phosphate fire retardant gels with and without boric acid addition. Solid-state NMR spectroscopy in particular provides decisive results in this context, along with X-ray diffraction, infrared spectroscopy, elemental analysis and simultaneous thermal analysis. The combination of these methods provides information about the reaction mechanisms. It was shown that the gelation mechanism is due to the formation of an AlPO4 framework and that this formation is independent of the boric acid addition. In the case of intumescence, however, the boric acid addition is decisive, since it prevents melting of the hydrogel and intumescence already occurs at 130 °C (not before 270 °C without boric acid addition). Both intumescence mechanisms were elucidated and the role of boric acid was determined. With the addition of boric acid, covalently linked phosphates form via borate linkage already at a temperature of 130 °C, which increase the viscosity of the system and, together with the water vapor acting as a blowing agent, lead to foaming. Without boric acid addition, linked phosphates (polyphosphates) are formed only at temperatures above 250 °C, which are decisive for the viscosity increase and ...
Gelierungs- und Intumeszenzmechanismen von Aluminiumphosphat-Hydrogelen
Fire-resistant glazing consists of a pane composite with hydrogel fillings. These hydrogel layers place particularly high demands on the manufacturing process and the formation of a heat-blocking foam after intumescence in the event of fire. The hydrogels used today are mostly based on polymers or water glass systems and have limited temperature resistance, which is why new hydrogel fillings are being sought. Systems based on aluminium phosphate (Al(H2PO4)3 + monoethanolamine (MEA) + boric acid) are promising candidates. However, these systems lack fundamental understanding of the mechanism involved in the preparation process (gelation) and in the intumescence of the hydrogel. In this work, various characterization methods are used to elucidate the structural composition and temperature-induced changes during the foaming of aluminium phosphate fire retardant gels with and without boric acid addition. Solid-state NMR spectroscopy in particular provides decisive results in this context, along with X-ray diffraction, infrared spectroscopy, elemental analysis and simultaneous thermal analysis. The combination of these methods provides information about the reaction mechanisms. It was shown that the gelation mechanism is due to the formation of an AlPO4 framework and that this formation is independent of the boric acid addition. In the case of intumescence, however, the boric acid addition is decisive, since it prevents melting of the hydrogel and intumescence already occurs at 130 °C (not before 270 °C without boric acid addition). Both intumescence mechanisms were elucidated and the role of boric acid was determined. With the addition of boric acid, covalently linked phosphates form via borate linkage already at a temperature of 130 °C, which increase the viscosity of the system and, together with the water vapor acting as a blowing agent, lead to foaming. Without boric acid addition, linked phosphates (polyphosphates) are formed only at temperatures above 250 °C, which are decisive for the viscosity increase and ...
Gelierungs- und Intumeszenzmechanismen von Aluminiumphosphat-Hydrogelen
Göbgen, Kai Cedrik (Autor:in) / Roos, Christian Hans-Georg / Rädlein, Edda
01.01.2023
Aachen : RWTH Aachen University 1 Online-Ressource : Illustrationen (2023). doi:10.18154/RWTH-2023-12015 = Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2023
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