Introduction to Silicone Structural Adhesive

Some Silicone Structural Adhesive

As we have introduced about the products which are processed from silicone oil, many of them are in liquid or half-liquid forms. Today, we are going to introduce another solid form material which is widely applied in construction & building industry – the silicone structural adhesive.

The silicone structural adhesive is always a mixture of different components. It usually contains silicone oil, the thickener, A group adhesive and B group adhesive. These materials will be added one by one to the final black solid form adhesive. It is suitable for structural sealing of glass, stone, aluminum curtain wall and other constructive materials.

Categories and Properties of Silicone Structural Adhesive

It is to introduce the properties of silicone structural adhesive; we need to introduce them by their categories.

The first common type of silicone structural adhesive is the double component silicone structural adhesive. It has the following characteristics: it is mixed of A and B adhesive with a volume ratio of 10:1. This ratio gives grant the final mature adhesive the property of neutral solidification which makes the sealing process more straight and plain. The corresponding excellent adhesion to metal, coated glass, concrete, marble, granite and other building materials made itself to be way more suitable to be construction adhesive rather than other materials. Also, this adhesive no needs other primary coat for most materials, which means it has excellent consistency with other neutral silicone sealants. However, it does have some weaknesses. It is unsuitable to be used for all the materials that will seep oil, plasticizers and solvents which will definitely reduce the effectiveness of the adhesion; it is also not good to be used in moist, frost or damp places; People also do not use the product if the surface temperature of materials exceeds 35℃. In general, the product has a stricter requirement on temperature. Thus, the materials of the adhesive, especially the B group adhesive should be sealed strictly or it will be facing hydrolysis failure.

The second type is the double component hollow glass silicone sealant. It is mainly used as the second sealant for insulating glass (external seal). It has neutral solidification, non-corrosiveness to such construction materials as metal, coated glass, concrete, marble, granite, and other materials. When solidifying, the low molecular weight substances release will be a pretty good feature. It also has outstanding resistance to climate aging performance, resistance to ultraviolet rays, resistance to ozone and resistance to water. It has the good compatibility like other neutral silicone gel, but it needs to receive compatibility test before any use. The mixing ratio of A:B is also 10:1.

The double component insulating glass elastomer sealant is used for processing insulating glass and other uses as well. It has almost the same properties as the double component hollow glass silicone sealant and has the same mixing ratio of A:B at 10:1. Both of the two types of sealants are needed to be stored between -20℃ and 27℃.

Another type is the hot melt sealant. It is hot-melt insulating glass butyl-sealant and it has excellent adhesive performance with glass aluminum framework, and it also has high-airtightness; it has strong anti-ultraviolet nature and a broad range of use in different temperature rather some other types of adhesives mentioned above. It is mainly applied as the first sealing for insulating glass (inner seal) and is mainly used in insulating glass production and other usages. However, it still shares some common weaknesses with other ones. It must be dry and be clean for the adhesive interface; the users must make sure to use the specialized extrusion equipment for insulating glass product and latex coating temperature should be 125~135℃ in summer and 135~145℃ in winter; the corresponding working environment should not be below 5℃.

Compatibility of Insulating Glass Adhesive

Sometimes, the adhesives may have problems such as different compatibility. It mainly refers to the sealing adhesives used in making insulating glasses and in installing they are compatible. This will lead to butyl adhesive to be dissolute and make the first butyl adhesive to ineffective in a certain period and lead to the corresponding ineffectiveness of the insulating window glass.

Here lists some common phenomenon:

1.      The butyl adhesive is dissolute and becomes thin and inner spreads, and even displays the phenomenon like flowing.

2.      The butyl adhesive is dissolute slowly and appears the increment of widths of some spots and breach inside the glass.

3.      The butyl adhesive is dissolute, reshaped and spreads to break the continuously regular butyl adhesive strips on the both sides to make the first sealing to be ineffective.

The reason why these occurred is the butyl melting sealing adhesive’s main based materials like polyisobutylene and butyl rubbers will be dissolute. The solvent mainly comes from the external sealing adhesive of the insulating glass or engineering sealing adhesive which is coated during in the installation of the insulating glass. These adhesive contain solvent materials which could dissolute the butyl sealing adhesives and they are usually the palsticizers which contain mineral oil.

The corresponding solution is that to make compatibility test of the first butyl melting sealing adhesive and the second double component sealant when manufacturing the insulating glasses to ensure they could be compatible with each other. This test could be done by the supplier, by the technicians of the buyer and any other qualified third parties. When installing the insulating glasses, the compatibility test must be done of the sealing material used in installing insulated glasses and the first butyl sealant for insulating materials to ensure they could be dissolute mutually.

Sometimes the manufacturer of insulating glass and company that install the insulating glass are different, thus the arrangements for the compatibility tests must be prepared at an early stage.

Summary

The application of silicone structural adhesive is narrow due to they are mainly applied in construction field only. However, they are so effective in the field that few products could replace the high values they performed in the industry.