M.Sc Thesis

M.Sc StudentBuk Ahuva
SubjectSynthesis of Intumescent Layers for Fire Resistant
DepartmentDepartment of Energy
Supervisors PROF. Gideon Grader
DR. Gennady Shter


Fire resistant glass (FRG) windows serve as ordinary outdoor windows or as indoor partition walls but become a lifesaving thermal insulation barrier under fire condition. The transition between a normal transparent glass to an opaque insulating barrier is based on a foaming reaction that takes place in a transparent gel (called an intumescent layer) that is placed between two glass sheets. Foaming is initiated upon heating the intumescent layer above a certain temperature limit. The layer turns into a stable ceramic foam that reduces the fire heat flux, isolating the area that is under fire and smoke for at least 30 minutes. This provides sufficient time for safe evacuation of the building.

The goal of this work was to prepare intumescent layers that satisfy the requirements of transparency and strength for long time, and finally provide thermal isolation and safety barrier for more than 30 minutes at fire conditions. The product had to remain stable at any environment (cold or hot) and had to be assembled by the "Cast in place" (CIP) method. The CIP method involves pouring a solution between two glass panes and curing the solution to form a gel interlayer. The research is focused on understanding the process and on finding the appropriate materials, additives and its concentrations for achieving the desirable properties. In addition, we studied the effect of processing conditions and variable parameters on the final FRG properties.  During the research we encountered different problems such as: bubbles appearance, discoloration, low transparency, high haze, soft gels and un-pourable precursor. The intumescent interlayer comprised of potassium water glass, various additives and special submicron powder that was synthesized by hydrolysis and condensation in emulsion of TEOS, water and ethanol. 

 Morphology characterization of the synthesized powder included high resolution scanning electron microscopy imaging and specific surface area measurements (B.E.T). The thermal behavior of the powder was characterized by thermal gravimetric analysis coupled with online mass spectroscopy and FTIR spectroscopy. Characterization of the FRG interlayer included optical analysis of transparency/haze, in-situ gel rigidity and fire resistant testing.

Finally, fire resistant glass based on intumescent interlayer was successfully produced by the "cast in place" method. The produced FRG meets the requirements of modern uses and standards accepted worldwide to day.