Fire engineers have long struggled with a stubborn weak point in high-rise buildings: the sealant lines that close joints and service penetrations in fire compartments. A new study reports a modified silicone sealant loaded with silica aerogel and nanographene flakes that, in standardized fire resistance testing, satisfied both integrity and insulation criteria for more than 60 minutes, while a conventional control formulation failed after roughly 40 minutes of heating.
The research, published in the journal Architectural Research, was carried out by Do Su Yoon, Kee Sun Park and Sumin Kim. The team set out to solve a familiar trade-off in firestop materials. Conventional fire-resistant sealants rely on large quantities of inorganic fillers such as aluminum hydroxide and iron oxide, which improve fire performance but degrade the elasticity and adhesion that sealants need to survive daily building movement and long-term aging.
The material logic behind the new formulation rests on two complementary nanomaterials. Silica aerogel is a nanoporous solid with porosity exceeding 90 percent and an ultralow thermal conductivity of approximately 0.013 W/(m·K) at room temperature, among the lowest values reported for any solid material. Inside a sealant, its nanoporous structure interrupts heat-transfer pathways and suppresses temperature rise on the unexposed side of a joint during fire exposure. Nanographene flakes, two-dimensional platelets roughly 1 nanometer thick with a high aspect ratio, act as physical barriers that impede the migration of gases and heat and promote the formation of a dense char layer that blocks oxygen ingress and flammable decomposition gases.
Both nanomaterials, however, tend to agglomerate in polymer matrices because of their high surface energy, weakening interfacial bonding and creating defect sites. To counter this, the researchers applied surface modification strategies: atmospheric-pressure plasma treatment to generate chemically reactive functional groups on particle surfaces, followed by immersion of the silica aerogel in an aqueous ammonium phosphate solution and of the nanographene flakes in a silane emulsion, inducing chemical crosslinking between the resin and the nanomaterials.
The experimental design compared five formulations built on 100 parts by weight of modified silicone resin, with plasticizer, reinforcing silicon dioxide, curing agent and calcium carbonate held constant, and aluminum hydroxide and iron oxide uniformly included in all groups. The control group contained no nanomaterials. Experimental Groups 1 through 3 added untreated silica aerogel and nanographene flakes in stages, along with boron-treated titanium, which forms a vitreous protective layer at high temperatures, and Pigment Yellow 181, a benzimidazolone compound whose N–H groups act as radical scavengers that interrupt thermo-oxidative degradation chains. Experimental Group 4 matched Group 3 but used the surface-modified nanomaterials.
Mechanical testing showed clear gains from interfacial control. All experimental groups outperformed the control tensile strength of 28 kgf/cm², with Group 1 improving by 28.57 percent and Groups 2 and 3 by 35.71 percent each. Group 4 reached 41 kgf/cm², a 46.43 percent improvement over the control, which the authors attribute to better nanoparticle dispersion and more efficient stress transfer at the matrix–filler interface. Adhesion strength, which changed little in Groups 1 through 3, rose to 30 kgf/cm² in Group 4, an increase of approximately 15.38 percent, reflecting mechanical interlocking and stronger chemical bonding at the substrate interface.
Thermal and flame-retardant results reinforced the pattern. In thermogravimetric analysis, the control group lost an additional 15.15 percent of its mass in the high-temperature decomposition stage following primary degradation above 200 °C, whereas the experimental groups recorded additional losses of only 0.1121, 0.1042, 0.1021 and 0.1089 percent, with Group 3 showing the lowest value. All experimental groups achieved the highest UL-94 vertical burning classification of V-0 with no cotton ignition from dripping, and Group 4 showed the shortest after-flame time, about 5 seconds, along with the most uniform char layer. After accelerated thermal aging at 200 °C for four weeks, Group 4 retained more than 85 percent of its initial tensile strength.
The decisive test followed KS F 2845, in which 7-millimeter sealant layers on tempered glass assemblies were exposed to the standard fire temperature curve for 60 minutes. The control group reached the critical temperature rise on its unexposed surface at about 37 minutes and showed flame penetration at 40 minutes, failing the criteria. Experimental Groups 1 through 4 maintained stable performance throughout the required duration without flame penetration, satisfying integrity and insulation requirements. The authors attribute this to the aerogel suppressing early heat transfer while the graphene-reinforced char layer blocked oxygen ingress and heat diffusion at elevated temperatures.
The study frames the performance as a sequential composite defense mechanism: the aerogel shields the matrix and keeps internal temperatures below roughly 200 °C in the initial phase, aluminum hydroxide decomposes endothermically above about 220 °C to release cooling water vapor, and the nanographene flakes restrict gas migration and build a char skeleton between roughly 300 and 600 °C that also protects the porous aerogel framework from collapse above 600 °C. Experimental Group 4 was identified as the optimized formulation, balancing tensile properties, thermal durability and fire resistance.
The findings are laboratory-scale results on formulated specimens rather than field-verified installations, and the fire resistance evaluation covered a 60-minute test duration. Even so, the authors argue the hybrid system demonstrates substantial potential for improving the reliability of firestop systems in building envelopes and compartmentation, addressing the vulnerability of organic sealants that soften, shrink and lose adhesion under high temperatures and thereby open pathways for flame and toxic gas spread in high-rise and large-scale buildings.
Subject of Research: Development and fire performance testing of a hybrid modified silicone sealant incorporating silica aerogel and nanographene flakes for firestop linear joints in buildings
Article Title: A Hybrid Modified Silicone Sealant for Firestop Linear Joints: Toward Fire-Resistant Sealing Integrated with Architectural Finishes
Article References: Yoon, D. S., Park, K. S., & Kim, S. (2026). A Hybrid Modified Silicone Sealant for Firestop Linear Joints: Toward Fire-Resistant Sealing Integrated with Architectural Finishes. Architectural Research, 28(1), Article 13. https://doi.org/10.1007/s44515-026-00015-z
Image Credits: AI Generated
DOI: 10.1007/s44515-026-00015-z
Keywords: firestop sealant, modified silicone, silica aerogel, nanographene flakes, fire resistance, KS F 2845, UL-94 V-0, interfacial modification, plasma treatment, thermal aging, building compartmentation, char layer
News Source: Denise Maddox. (October 29, 2026). Hybrid Silicone Sealant Withstands Fire for Over an Hour in Building Joints. Scienmag.
