The current curtain wall design promotes the principle of energy efficiency, which puts higher demands on the sealing effect of the wall. The sealing effect is mainly related to the correct application of the sealant on the curtain wall.
1 Several options for silicone rubber weathering applications
In the weathering application of sealant, it is necessary to pay attention to the choice of suitable sealant, the aspect ratio of sealant, the choice of gasket and so on.
1.1 Selection of appropriate sealant
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.
1.2 Sealant width to depth ratio selection
The width-to-depth ratio of the sealant is generally recommended to be 2:1, the minimum width and depth of the glue is 6 mm, and the depth of the glue is not more than 12 mm. In some cases, 1:1 is acceptable, but the aspect ratio cannot be less than one. This is because when the depth is greater than the width, the displacement ability of the sealant will be reduced, and the displacement capacity estimated by the original design cannot be achieved. When a large displacement phenomenon occurs, the adhesion stress may even become large. Fall off.
1.3 Selection of gaskets
The function of the gasket material, in addition to effectively controlling the depth of application of the sealant, increasing the contact surface with the substrate (for the use of a circular gasket only), it is also possible to prevent the occurrence of three-sided adhesion, thereby Avoid possible cohesive failures. For the choice of gasket, it must be noted that the sealant used is compatible and non-adhesive. Commonly used compatible gaskets are closed cell polyethylene liners or open cell polyurethane liners. The size of the gasket is greater than about 10% to 25% of the gap width so that the seam can be held without dents when the glue is scraped. When installing the gasket, try to avoid scratching the surface of the gasket to avoid so-called deflation.