The difference between the silicone sealant and the polysulfide

Insulating glass is a deep processing of glass products, but also a wide range of energy-saving materials. In recent years, the hollow glass industry has been rapid development. From the past only for high-end construction of special products, quickly to ordinary buildings, air-conditioned trains, air-conditioned buses, refrigerators, display cabinets and other areas of popularity. Especially with the promotion of plastic window application, the hollow glass is deep into the ordinary residential. At present, China's urban home air-conditioning has a high rate, such as Shanghai has reached 60% to 70%, according to experts estimate that the building interior temperature for each 1 ℃ lower energy consumption is increased by 6 times 6 ℃. The resulting increase in building energy consumption, increased environmental pollution. Therefore, the former Vice Minister of Construction Ye Rutang in the national building energy efficiency work conference pointed out that "window glass as soon as possible in one step, the full use of insulating glass.

Butyl rubber has the lowest water vapor transmission rate, silicone rubber is higher, but butyl rubber is thermoplastic, only used for inner seal, generally not used alone. Polysulfide rubber has a low permeability, is the ideal material for the manufacture of insulating glass (see Table 1)

Insulating glass sealant is the main factor in determining the quality performance of insulating glass. Insulating glass thermal insulation, sound insulation and frost protection are achieved through its inner sealed and dry air.

So the materials gas barrier and permeability is the key factor for the insulating glass quality.

Butyl rubber has the lowest water vapor transmission rate, silicone rubber is higher, but butyl rubber is thermoplastic, only used for inner seal, generally not used alone. Polysulfide rubber has a low permeability, is the ideal material for the manufacture of insulating glass (see Table 1).

 

The vapor permeability of the sealant  Table 1  Unit g/m2 · 24h

 

Polysulfide sealant

Butyl hot melt adhesive

Polyurethane sealant

Silicone sealant

Water vapor transmission rate

2.4

0.2

23.2

18

With the continuous improvement of energy requirements, in order to enhance the insulating properties of insulating glass, inflatable (argon, xenon) insulating glass is the development trend of insulating glass, which inevitably requires hollow glass sealant with good gas barrier properties or lower Of the air permeability.

Leakage is one of the main factors that cause the natural failure of insulating glass. Compared with polysulfide, the permeability of silicone rubber is 8 times that of polysulfide, and the service life of hollow glass sealed with silicone rubber is greatly reduced The Due to the high permeability of the silicone rubber, in order to ensure the quality and service life of the insulating glass, the use of silicone rubber for the production of insulating glass is limited, such as JC / T486 "elastic sealant for insulating glass "The standard stipulates that" the silicone is only used for silicone structural sealant bonding assembly of the glass structure system. "

At present, there are some hollow glass manufacturers use single-channel seal (that is, do not use hot-melt butyl rubber to make the inner seal), the use of this production process cannot use silicone rubber, or cannot guarantee the quality of insulating glass.

 

Several common insulating glass sealant performance comparison table 2

Variety

Adhesive

Water vapor permeability

Tectonic strength

Weather ability

other

Polysulfide sealant

good

small

Big

good

There are many examples of good applications in the world

Silicone sealant

Poor water resistance

Big

Big

good

Low molecular weight components easily dispersed, easy to contaminate the surface layer

Polyurethane sealant

good

small

Big

Surface easy to deteriorate

Less applications in the world

Butyl hot melt adhesive

Low temperature adhesion is poor, non-chemical bonding

Very small

small

Not good

Only used for insulating glass inner seal

The water resistance of silicone rubber is worse than that of polysulfide, and the water resistance and chemical solvent performance of the material are also important indexes of hollow glass sealant. For example, LOW-E (low-emissivity glass) insulating glass is the best energy-saving insulation, but it is very demanding on the water resistance of the sealant because the coating of the LOW-E glass is broken with water. New air-conditioned train windows are used in insulating glass. The hollow glass leakage is the common problem of the current train window, the reason is due to the glass and window frame quality easy to accumulate rain, after the sun, the water temperature up to 80 ℃ or so, under this condition, glue bonding Strength will be reduced rapidly, coupled with the vibration of the train running, glue and glass will be between the sticky and lead to failure of insulating glass. In terms of our accumulated experience, even if the water resistance of the better polysulfide, but also the formulation of the special design, the ingredients to be selected in order to meet the requirements.

Finally, from the product price factor, the proportion of silicone rubber, although smaller than the proportion of polysulfide, that is the same weight of the former can play more to extend the rice, but the former price was significantly higher than the latter, integrated down, the use of polysulfide Still more than silicone rubber economy, and silicone rubber permeability, permeability is much higher than the polysulfide, to achieve the effect of polysulfide, it is necessary to increase the thickness of the adhesive layer, will inevitably improve the production cost of insulating glass.

In recent years, the market also appeared in the production of insulating glass insulation, this structure in the technical there are shortcomings. Since the main material of the strip is butyl or polyisobutylene, the strip forms a non-chemically bonded surface on the glass under heating and pressurized conditions. Therefore, the temperature resistance and the weather resistance are poor (butyl or poly Isobutene gel heat creep, cold case is hardened). Moreover, the strip is a thermoplastic rather than an elastomer, so the displacement resistance is poor. From the actual use of results, many of the production of this method to reflect the hollow glass leak, water leakage is serious.

Polysulfide sealant is the earliest use of hollow glass industry is currently the most widely used outer sealant. In recent years, despite the silicone, polyurethane and other rubber species competition, but its excellent overall performance and moderate price still occupy the dominant position. From the world market, in 1999 the world's hollow glass production of 257 million square meters, of which the European market accounted for 54%. In the European market, polysulfide sealant accounted for 82% of the total amount of insulating glass, the Japanese market, polysulfide sealant share of up to 90%.

In short, in the choice of insulating glass sealant should pay attention to: (1) for the construction of doors and windows, open frame glass curtain wall, air conditioning train or bus, freezer and other insulating glass should choose butyl-polysulfide system (butyl rubber for inner seal, Polysulfide for outer seal). (2) For the full or semi-hidden glass curtain wall with hollow glass should be selected butyl-silicone structural adhesive system. Here silicone structural adhesive to bear the structural strength, the general thickness of the adhesive layer should be between 10 ~ 20mm.