Formulation Design and Evaluation for Performance Balancing of Fire-Resistant Polysulfide Sealants: Analysis of Mechanisms for Enhancing the Physical Properties of Fire-Resistant Compositions Using Cotton Fibers and Adhesion Promoter

This study investigated composite formulation design strategies to address the decline in mechanical properties that occurs during the process of ensuring the fire-resistance performance of two-component polysulfide sealants. To overcome the reduction in matrix cohesion and adhesion caused by the high loading of inorganic flame retardants, amino-silane-based adhesion promoters and high-aspect-ratio cotton fiber powder were introduced, and the resulting thermal and mechanical reinforcement mechanisms were evaluated. The experimental results confirmed that, owing to the formation of chemical interfacial cross-linking and three-dimensional stress transfer pathways, the tensile strength significantly increased to 37 kgf/㎠ (3.63 MPa) (23.3% improvement, p<0.05) compared with that of the control group (30 kgf/㎠ (2.94 MPa)), and the adhesive strength improved to a maximum of 31 kgf/㎠ (3.04 MPa) (p<0.05). Furthermore, through the combined action of metal hydroxides, expanded graphite, and zinc stannate, a 60-min fire resistance and heat-insulation performance were achieved in accordance with the KS F 2845 standard. In high-temperature environments, this performance was further enhanced by the physical support provided by the cotton fibers, resulting in the maintenance of dimensional stability without sealant sagging. In conclusion, this study derived empirical formulation conditions for sealants used in fire-resistant glass assemblies that could simultaneously satisfy both extreme fire safety and structural reliability requirements.