Sealed ball bearings, as shown in Figure 9, refer to ball bearings equipped with sealing rings. They are divided into two types: non-contact sealing rings and contact sealing rings. Rubber sealing ring material, nitrile rubber is used for normal use. In addition, according to different temperature requirements, materials such as polypropylene rubber, silicone rubber, and fluorine rubber are used. These rubbers have their own specific properties and should be selected according to the purpose when used. Table 6 lists the main characteristics and suitable temperature ranges of various rubber materials. The applicable temperature range in Table 6 is a reference index for continuous use. The thermal aging of rubber is related to temperature and time. Suitable time and frequency of use may reach a larger temperature range. The frictional heating of the non-contact sealing ring lip can be ignored. The heating factor that causes rubber aging is only the physical change caused by the ambient temperature and the bearing temperature. Therefore, even if it is hardened by heat aging or loses its elasticity, the impact on the sealing performance can be greater than that of the contact type sealing ring. It is also minimal. On the contrary, the wear caused by the friction of the lip of the contact seal ring, thermoplastic deformation, hardening, etc. are all major problems. In the event of wear and plastic deformation, the contact pressure with the sliding surface of the lip will be reduced, and then a gap will be generated. However, even if there is a gap, its value is within the minimum limit, so the sealing performance such as dust and grease leakage will not be significantly reduced. Therefore, even a little plastic deformation or sealing performance such as grease occurs. Therefore, even if there is a little plastic deformation or increased hardness, it will often be used without hindrance. However, when there is a lot of garbage or water in the external environment, the bearing sealing ring is only used as an auxiliary sealing ring, and the main sealing ring must be designed separately. As mentioned above, although the applicable temperature range of rubber materials is a reference when selecting models, because heat-resistant rubber is expensive, the key to selecting models is more economical and reasonable, and the key is to fully grasp the temperature requirements. Moreover, it is not only limited to heat resistance, but also the characteristics of various rubbers should be fully compared.