When applying silicone, airs enter it. Poor working conditions. It is not easy to evenly apply silicone and air may easily trapped in sealed joints.
When applying silicone, the surface of joints is moist If you apply silicone when joints are still wet after raining, you may see bubbles from soft joints. This is because the surface of joints is exposed to the sun and its temperature rises so that moisture inside them may be evaporated and bubbles appear.
Honeycomb bubbles appear inside joints because silicone is exposed to the sun when it is not cured.
The temperature of the material surface is too high: When the material surface is higher than 50℃, chances are that bubbles appear in joints.
When there is a big temperature difference between day and night, the thermal expansion may become larger at joints
This easily occurs when applying silicone to aluminum curtain wall. The aluminum plate has a larger coefficient of expansion with larger thermal expansion and joint movement. During the curing, larger and repeated joint movement can cause bubbles.
Q : Silicone turns yellow after curing
The reason why silicone turns yellow is due to materials it comes into contact with. This is a common case where silicone is applied to black rubber strips around the aluminum window frame. Because some rubber has poor quality, silicone is likely to go yellow over time after it comes into contact with it.
In addition, precipitable or volatile substances may be added to rubber strips, which contaminate silicone.
Q : Cured silicone turns white after stretched
Many types of silicone are added with solid fillers to increase their strength. After they are stretched, these solid fillers turn white so that it looks whitish.
Q : When squeezing silicone, air bubbles appear or I cannot smoothly squeeze it out
Especially for low quality silicone, many bubbles are formed because it is stored under a lower temperature and it contracts accordingly. It is recommended not to store it in a temperature below 0℃.
When air bubbles are present or it cannot be squeezed out smoothly (large bubbles), this means that it is not produced properly.
Q : Wrinkles appear when silicone is cured
This is mainly because the coating layer is too thin when applying to the surface of two materials. Different materials have different coefficient of thermal expansion so a large temperature difference will cause acid sealants to deform or have wrinkles when they are not fully cured.
Solution: Apply a thicker layer. When applying, this layer is about 1mm. It is recommended to increase the layer thickness to 1.5mm - 2mm.
Q : After apply silicone to the back of a mirror, why are there adhesive shades
There are usually three different coatings on the back of a mirror: mercury, silver, and copper.
The above problem may be due to the use of acid silicone that reacts with the coating layers so that you can see adhesive shade.
You should, therefore, select neutral silicone where there are two types: Alkoxyl Type and Oxime Type.
This will not happen if you use the Alkoxyl neutral sealant. Before application, It is recommended to perform the compatibility test to check if silicone is compatible with materials to avoid unnecessary loss.
Q : Some acid sealants cause discoloration of of aluminum materials
During the curing process, acid sealants release acetic acids that are corrosive to metal materials. As there is a oxide film on the surface of the aluminum material, they can used on it. Generally, silicone does not cause discoloration of aluminum materials.
The quality of aluminum materials are mainly based on the the coating layer of the aluminum material. For example, if the coating has poor adhesion or is too thin, it will cause discoloration after applied.
Improper application also causes discoloration. After application, if aluminum materials are placed in a place without good ventilation, acetic acids released during silicone curing may not clear away timely, which causes higher local concentration and that aluminum material, in turn, will be corroded over time.
Q : Why does the sealant not provide good adhesion to some construction materials (aluminum materials, aluminum composite panels, section steel)
There are a wide variety of construction materials in the market now. Take aluminum materials for example. There are sprayed and anodized ones.
For spray aluminum, there are several coatings used with different surface properties. You need to carry out tests to know how good is its adhesion to them. In addition, section steel is made of PVC with addition of plasticizer and fillers. Furthermore, many manufacturers use so many raw materials that it is difficult to gain insight into it.
The influential factors above are not easily observable so we recommend to perform the compatibility test before application.
Q : Why silicone contracts after curing
Silicone always contracts after curing but there is a big difference in terms of rate of contraction.
For example: High quality silicone only contracts by 5% in size while low quality may contracts by 30% or above in size. This is because low quality silicone is incorporated with fillers that will be volatile in the air over time. The more fillers it has, the bigger rate of contraction it has.
Q : A small amount of silicone oil is present on the nozzle
This is because silicone has been placed for a long period of time, which does not affect its use and performance.