In addition to the good adhesion of the selected silicone sealant to the material being contacted, sufficient displacement capability is required to meet the design requirements. Taking a piece of 2000 mm × 1000 mm aluminum plate as an example, the coefficient of thermal expansion is about 23.2 × 10 - 6 ° C - 1 . When the temperature difference of the material surface is 70 ° C, the displacement of the aluminum plate due to the temperature difference can be calculated according to the formula. Displacement due to thermal expansion and contraction = length of aluminum plate × thermal expansion coefficient of aluminum material × temperature difference (1)
= 2000 × 23.2 × 10 - 6 × 70
= 3.25 (mm)
If the width of the expansion joint and the displacement caused by thermal expansion and contraction are known, the displacement capacity of the required sealant can be calculated according to formula (2).
Minimum gap width = thermal displacement × (100 / sealant displacement capacity) (2) Assuming that the width of the expansion joint designed in this example is 6.5 mm, then: 6.5 mm = 3.25 mm × 100 / The displacement capacity of the sealant is calculated. The displacement capacity of the silica gel is required to be ±50%. Therefore, a silicone sealant having at least ±50% displacement capability must be selected for this design. In practice, the influence of the construction error of the glue joint should also be considered, which is decided by the designer.