Sealant is mainly used for the joint sealing of window frame and glass, and the joint sealing of window frame and inner and outer walls, which plays a key role in the water tightness, air tightness, heat preservation and sound insulation of doors and windows. Problems in the application of sealant for doors and windows will lead to the sealing failure of doors and windows, water leakage, air leakage and other problems, which will seriously affect the overall quality of doors and windows. In this issue, Baiyun online introduces some common problems in the application of sealant for doors and windows. By analyzing the causes, it provides solutions to help users use the sealant well. First of all, I will introduce three common problems to you: incompatibility, poor adhesion and storage.
① incompatibility
Some accessory materials used in door and window assembly, such as rubber materials (rubber pad, rubber strip, etc.), usually have close contact with sealant. However, some rubber products may be added with rubber oil or other small molecular substances incompatible with sealant system in order to reduce cost or other considerations. When this kind of rubber products contact with silicone sealant, rubber oil or other small molecular substances will migrate to the sealant, or even to the surface of the sealant. In the process of use, under the effect of ultraviolet radiation in the sun, the sealant may turn yellow, which is more obvious on the door and window glue with lighter color.
The sealant on a door and window turns yellow. It is found that the door and window sealant is incompatible with the rubber strip of the joint after cutting the adhesive joint (as shown in the figure below).
Figure 1: discoloration of sealant (left) and contact with incompatible rubber (right) after cutting
Therefore, we suggest that before the construction of sealant, the compatibility test of sealant and its contact materials should be carried out according to the compatibility test method in Appendix A of GB 16776 to determine the compatibility of sealant and base material, and the construction should be carried out according to the requirements of the compatibility test results. As shown in the figure below.
Figure 2 compatibility test
In the above figure, the left sample block is a rubber strip compatible with silicone rubber, without discoloration; the middle sample block is a rubber strip incompatible with silicone rubber, with discoloration; the right sample is a reference white silicone rubber, without discoloration. It can be seen that the compatibility test before construction can effectively avoid the incompatibility between sealant and accessory materials.
② poor adhesion
In the application of door and window glue, the base materials that may contact are glass, aluminum, cement mortar, ceramic tile, wall paint, etc. The surface of these materials is likely to have oil stain, dust or other residual substances. If the adhesiveness is not confirmed before construction, it may cause poor adhesion of door and window adhesives. As shown in Figure 3, the sealant on a door and window does not adhere to the aluminum material. The main reason is that there may be some oily substances on the surface of the aluminum material. If it is not cleaned, the sealant will be applied directly, which affects the bonding effect between the sealant and the aluminum material.
Fig. 3 no bonding between door and window glue and aluminum material of window frame
If the door and window glue is used at the joint between the door and window and the cement mortar outer wall, and the dust and sand on the cement mortar surface of the outer wall are not cleaned, it is likely that the sealant will not stick to the cement mortar outer wall after curing (see Figure 4).
Figure 4: the door and window glue is not bonded to the cement mortar of the outer wall (left) and there are many dust and sand grains on the bonding surface (right)
Therefore, in the actual process of using adhesive, it is necessary to pay attention to the pretreatment of the surface of the substrate to be adhered, and use appropriate methods to remove the oil, dust, sand, loose layer, etc. on the surface of the substrate to be adhered, so as to achieve the ideal bonding effect between the sealant and the substrate.
③ sealant storage
Sealant products belong to chemical products, which have a certain storage period and are required to be used within the storage period. If the sealant has exceeded the storage period, it is likely that the curing speed will be significantly slower, poor curing or even non curing.
According to the requirements of storage conditions in relevant standards of sealant, the nominal storage period of sealant is under 27 ℃ and under cool, dry and ventilated conditions. If the storage environment in actual use cannot meet the conditions specified in the standard, for example, if the ambient temperature is too high, the storage period of sealant may be shortened. Even if the storage period of sealant does not exceed the nominal, the phenomenon of slow curing will occur.
Affected by the epidemic situation, some enterprises, construction units and users may store some door and window glue products. We hereby remind you to confirm the storage period and storage environment of sealant after resumption of work. Before large-scale construction, the basic performance of sealant can be tested. In the previous articles, we have introduced the surface dry time test, debonding time test and elastic test of sealant. (see Figure 5, 6 and 7)
Figure 5 table dry test
Fig. 6 debonding test
Figure 7 elasticity test
Through the above three tests, we can test the surface drying, anti adhesion, elasticity and other properties of sealant. After confirming that the sealant performance is normal, carry out the construction to ensure the construction quality and the overall performance of doors and windows.
The first part of Baiyun online about the common problems of sealant for doors and windows will be introduced here temporarily, and the other related problems will be introduced in the next part.
By online
Source: Guangzhou Baiyun Chemical Industry Co., Ltd
Based on Association Service Industry
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