Flow properties of macromolecule-reinforced silicate hydrogels

Silicate hydrogels, due to their property of intumescence, are widely used as an inorganic inter-layer in a fire-resistant glass. However, being viscoelasic materials, these gels sag as the interlayer thickness is increased. Several possibilities to solve this issue are first discussed in this work, which then focuses on modifying the composition of these silicate hydrogels in order to improve their flow properties, i.e., to increase their relaxation time to delay or even prevent sagging, without compromising on their transparency or fire-resistant properties. Before suggesting modifications in the composition of the silicate hydrogel, it is essential to first understand the formation of a silicate network, reviewed at the beginning of this document. These networks comprise reversible bonds that can break and reform. At high temperatures, the dissociation rate of these bonds is higher than their rate of formation which results in a loss of elasticity and therefore such systems creep after a long time. Rheology is an important tool to characterize the flow behaviour of materials. A major part of this thesis highlights the link between the chemistry of silicates and their rheological properties. Therefore, we also present the basics of viscoelastic materials followed by models to explain the behavior of hydrogels comprised of reversible networks. Data from the rheological characterization of silicate hydrogels are then compared with these models in order to understand their relaxation behavior. With an objective to ensure that the reinforcing agents are effectively bonded within the silicate network, several tests are performed in order to optimize a procedure. We then discuss the impact of reinforcement addition on the rheology of the prepared silicate gels.