How To Choose Insulating Glass Sealant?

With the improvement of modern decoration level, insulating glass is currently widely used in commercial office buildings, large shopping malls, high-rise residential buildings and other buildings of an energy-saving glass, with excellent thermal insulation, sound insulation performance and beautiful and practical. Insulating glass sealant in the cost of insulating glass is not high, but the durability of insulating glass and safety application is very important, then how to choose?

1.What's the insulating glass?

Insulating glass is made of two (or more) pieces of glass bonded to the spacer bar, the sealing type mainly adopts two kinds of adhesive strip method and bonding method, and the current use of more is the double-channel sealing structure of the bonding method, the two pieces of glass are separated by the spacer bar, the spacing bar and the glass are sealed by butyl glue, and the spacer bar is filled with molecular sieve. The gap between the edge of the glass and the outer side of the spacer strip is sealed with a second sealant.

The role of a sealant is to prevent water or inert gases from entering and leaving the cavity, generally using butyl rubber, because butyl rubber has very low water and inert gas permeability, and is the most effective barrier between the side of the aluminum strip and the glass to block water vapor. However, the butyl adhesive itself has low bond strength and small elasticity, and the overall structure must be fixed by two seals, and the glass plate and the spacer bar must be bonded together, so that the insulating glass can maintain a good sealing effect when it bears the load, and the overall structure is not affected.

2.Type of insulating glass sealant

Insulating glass sealant is mainly silicone, polyurethane and polysulfide three categories, but due to the polysulfide insulating glass sealant,polyurethane adhesive UV aging resistance is poor, if the adhesive surface with the glass is exposed to the sun for a long time, there will be a degumming phenomenon, will lead to the hidden frame glass curtain wall insulating glass sheet off or point support glass curtain wall insulating glass seal failure. The molecular structure of silicone sealant makes silicone sealant have the advantages of excellent high and low temperature resistance, weather resistance and ultraviolet aging resistance, and low water absorption, so the market is mainly based on silicone.

3.The harm of improper application

The problem caused by improper selection of second sealant can be divided into the following two categories: one is the loss of the use function of insulating glass, that is, the loss of the original function of insulating glass; The other involves the safety of insulating glass applications - that is, the safety risks caused by the fall of the outer pieces of insulating glass.

Insulating glass seal failure causes are usually:

a) The butyl adhesive itself has quality problems or is incompatible with silicone adhesive

b) The insulating glass is filled with mineral oil with a second sealant

c) Contact with oil-filled adhesives, such as weather-resistant adhesives on curtain wall joints or sealants on doors and Windows

d) Other factors such as desiccant or processing technology

The insulating glass has a sealing failure, and after several years of use, the insulating glass will have obvious condensation and water accumulation, and the effect of heat insulation, sound insulation and waterproof will be lost prematurely. These problems have a great relationship with the quality of butyl adhesive, molecular sieve quality and processing technology, but the quality and performance of the second sealant can not be ignored. Because the insulating glass structure must be fixed by two seals on the overall structure, the glass plate and the spacing strip are bonded together. Some insulating glass glue manufacturers lack experience in product formulation, or the level of quality control is low, resulting in fluctuations in product performance, poor adhesion between the second sealant and glass, spacer strips, or compatibility problems with a sealing butyl glue, seriously affecting the service life of insulating glass.

The most common reason for the failure of insulating glass due to silicone adhesive is that the second seal silicone adhesive used for insulating glass is an inferior and cheap oil-filled adhesive. Insulating glass second sealant filling oil will lead to insulating glass failure?

In order to reduce costs, some insulating glass secondary sealant on the market is filled with a certain mineral oil. Mineral oil, commonly known as white oil, is an alkane substance, which has poor compatibility with silicone sealant, and will migrate and exude after a certain time, forming a "rainbow" or "oil flow" phenomenon, and finally lead to the failure of insulating glass. The reason for the "iridescent" phenomenon is the migration of mineral oil into the inner cavity of the insulating glass. The reason for the "oil flow" phenomenon is that mineral oil migrates, dissolves a sealing butyl adhesive of the insulating glass, and produces black oil spots or oil stains.

Because the silicone base polymer accounts for a large proportion of the cost in silicone sealant, reducing the silicone base polymer content can reduce the cost. Poor manufacturers use some low-cost mineral oil to replace the silicone base polymer, at the same time, the mineral oil also significantly reduces the sealing adhesive viscosity, so the formula can be filled with a large number of fillers to further reduce the silicone base polymer content. The excellent weather resistance of silicone sealant is due to the silicone-based polymer containing silicone-oxygen bond as the main chain, if the content of silicone-based polymer decreases, it will inevitably lead to the durability of silicone sealant decreases, thus affecting the service life of insulating glass.

4.Second sealing adhesive selection precautions

Because the hollow glass sealant used for hidden frame, semi-hidden frame and point support glass curtain wall is subjected to the wind load and self-weight load of the outer glass, the adhesive strength of the sealant is required to be high. Although the bonding strength of silicone adhesive and polysulfide adhesive is high, due to the poor ultraviolet resistance of polysulfide sealant, and the poor compatibility with the silicone sealant used in the curtain wall, the insulating glass that bears the load, such as the hidden frame, semi-hidden frame and point support glass curtain wall, the second sealant must be made of silicone structural sealant. 

With the increasingly fierce market competition, some bad manufacturers in order to reduce production costs, at the expense of sealant product performance and quality to seek short-term profits. Filling cheap "mineral oil" instead of expensive silicon-based polymers is a common way for poor manufacturers to reduce sealant production costs. Behind the low durability of cheap oil-filled adhesive is the premature failure of insulating glass or even the fall of insulating glass outer pieces, which may cause significant losses. 

Therefore, we must refuse to use "oil-filled glue". Insulating glass secondary sealant acco`unts for a small percentage of the cost of insulating glass, but it is very important for the durability and safety of insulating glass applications. It is recommended that customers must choose the right product, such as the pursuit of low prices and ignoring the correct application and quality assurance of the product, which may lead to quality problems of curtain wall doors and Windows, and even cause major safety accidents.