*Surface Damage*

After aging at low temperature, the surface of the specimen significantly changed. The surface of the specimens without aging was relatively flat, and the micro-pits visible to the naked eye appeared on the surface of the specimens after 36 days of low-temperature treatment, and the number increased with time. At 90 days, pits and tiny holes appeared on the surface of the specimen in the water. At low temperature, the surface of the specimen became rough while the specimen became hard. The apparent morphology of the rubber is shown in Figure 6.

(**d**) After aging in low temperture water environment for 36 days

(**a**) At room temperature (**b**) After aging in low temperture air environment for 36 days

(**e**) After aging in low temperture water environment for 72 days

(**c**) After aging in low temperture air environment for 90 days

(**f**) After aging in low temperture water environment for 90 days

**Figure 6.** Apparent morphology of the specimen after aging at low temperature.

The surface morphology of the rubber waterstop before and after aging is further examined by SEM and is shown in Figure 7.

(**a**) At room temperture (**b**) After aging in low temperture air environment for 36 days

(**c**) After aging in low temperture air environment for 90 days

(**d**) After aging in low temperture water environment for 18 days

(**e**) After aging in low temperture water environment for 54 days

(**f**) After aging in low temperture

water environment for 90 days

**Figure 7.** Surface micromorphology.

As shown in Figure 7a, the virgin surface of the rubber waterstop was flat, with white and black additive particles uniformly distributed. As shown in Figure 7b, after 36 days aging under low-temperature air environment, the additive particles on the surface completely disappeared, but many protrusions appeared, and the surface of the specimen became abnormally uneven. With the increase in aging time, the protrusions increased. After 90 days, tiny holes appeared on the surface of the specimen, as shown in Figure 7c. As shown in Figure 7d–f, in the low-temperature water environment, the surface morphology of the specimens protruded, and after 54 days, the rubber surface appeared stepped stratification. After 90 days, the surface became rougher as the protrusion on the surface increased, and the stepped stratification phenomenon became more obvious.
