The reason why silicone weatherproof sealant foams during construction is multi-faceted and complicated. It is difficult to judge the cause of foaming by one method and one result.
(1) Construction reasons
1 wrapped in air when glued
Silicone sealants generally perform glue injection work at the construction site, and the working conditions are poor. Workers stand on the scaffolding and glue the glue. The uniformity of the glue is difficult to grasp, and the glue is easy to wrap in the air.
Measures: When filling the glue, pay more attention to the uniformity of the injection. Generally, the vertical glue sewing glue can be applied from the bottom to the top to overcome some foaming phenomenon. More important is the skill and responsibility of the work operator.
2 workers glue injection habits
In the injection molding construction, it is often found that many people like to use soapy water, detergent water, washing powder water, etc. to spray on the joint of the glue when the glue is injected, and then wipe it with the hand to ensure that the glue is not sticky, but no It is thought that the flowing water is absorbed by the foam strip, that is, the water is dried. As long as there is soap, detergent, washing powder on the foam strip, the glue will foam when it is smeared in the sun.
(2) Reasons for external construction conditions
1 wet condition
In outdoor work, rainfall is often encountered, especially in the summer in the south. It rains almost every day. If it rains, the interface is wet and dry, and the glue is injected directly. When the sun shines on the bonding substrate and the glue joint, the interface is inside. The temperature rises, the moisture inside the glue seam evaporates, and the uncured, softer glue seams are foamed. Sometimes the moisture of the polyethylene foam pad will cause the glue joint to foam.
Measures: During the construction, you should not be willing to make progress. After the interface is dry, re-injection can avoid the above situation.
2 sun exposure conditions
Silicone sealant can't be exposed to the sun before it is cured. Especially when the glue is just finished, the sun will be exposed to the sun, which will cause honeycomb bubbles inside the glue joint, which will cause the external seam of the glue joint. Silicone sealants are more noticeable when used. In the hot summer construction, this situation is not easy to overcome.
Measures: Avoiding sun exposure when injecting glue will overcome some foaming. In the morning, glue on the west or north side of the building, and in the afternoon on the east or south side of the building. After the glue is injected, the glue is solidified for a period of time, the surface layer has been crusted, and when the sun is sun-dried, with some resistance, some foaming can be overcome.
3 substrate surface temperature is too high
When the silicone sealant is cured, the temperature of the bonded material should not exceed 50 ° C. This conclusion has been approved by most silicone sealant manufacturers. When the surface temperature of the substrate exceeds 50 ° C, the glue is injected, which will cause the foam to be foamed. This will be the case when the metal panel curtain wall is weather-resistant. In the hot summer, when the sun is exposed to the metal plate, especially the surface temperature of the aluminum plate will reach 80 ° C, at this time, the injection can easily cause the foam to foam.
Measures: Select glue in the second half or cloudy days to improve the above situation.