From Flame-Retardant Films to Luminescent Mortars: Multifunctional Geopolymer Systems Across Scales

Geopolymers, composed of cross-linked Si–O–Al frameworks, represent a sustainable alternative to Portland cement, combining low environmental impact with tunable functional properties[1]. In this study, geopolymerization strategies were applied to two systems, inorganic mortars and composite films, evaluated through calorimetric and mechanical techniques. Fully inorganic luminescent geopolymer mortars were synthesized by incorporating Egyptian blue into a halloysite-based geopolymeric matrix. These mortars combine structural integrity with photoluminescent properties, opening potential applications in multifunctional coatings or smart construction materials. TGA was employed to monitor the degree of geopolymerization and assess thermal stability. The presence of Egyptian blue was confirmed through excitation and emission spectroscopy, validating its retention and optical activity within the geopolymer network. In parallel, Hydroxypropyl cellulose/halloysite nanotube (HPC/HNTs) composite films were developed for flame-retardant applications[2]. After geopolymerization, these materials exhibited outstanding flame-retardant behavior, rapidly self-extinguishing (≤0.5 s after ignition removal). The activation energy of the HPC degradation process was estimated using model-free isoconversional methods, allowing for an in-depth understanding of how the inorganic network influences thermal degradation mechanisms. DMA analysis confirmed enhanced mechanical performance, revealing increased stiffness and reduced damping, indicative of stronger interfacial interactions between the organic and inorganic phases. This dual-system approach demonstrates the versatility of geopolymers in the development of advanced functional materials, ranging from organic-inorganic flame-retardant composites to luminescent inorganic mortars. Calorimetric techniques, particularly TGA and isoconversional analysis, proved essential for elucidating the thermal behavior and evolution of the geopolymeric structure in both hybrid and fully inorganic systems.