S1 refers to a flexible category of cement-based adhesives with special deformation properties. Ceramic Tile Adhesives (JC/T 547-2017) stipulates that S1 means flexible and S2 means high flexibility. The lateral deformation index of S1 adhesive is 2.5-5mm, showing excellent flexibility, while S2 is ≥5mm, showing excellent flexibility.
  Flexible adhesives, as a "soft sandwich" layer, can effectively buffer the deformation difference between the substrate and the tile to avoid system damage. They are suitable for the paving of large-sized tiles, providing buffering during vibration or deformation, and enhancing the stability and durability of the paving system. Tests show that rigid adhesives are prone to breakage after bearing loads, while S2 adhesives show excellent deformation performance and can withstand large loads.
  The test of the JC/T 547 standard helps understand the flexible characteristics of adhesives and guides consumers to choose products that meet their needs. The flexibility of flexible adhesives is comparable to that of resin materials, ensuring the stability of the paving system in extreme environments.

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