Material Properties|Vacuum Glass

What is Vacuum Glass?

Vacuum glass is to seal two pieces of flat glass around them, and the gap is pumped into a vacuum (air pressure is less than 0.1Pa), the gap between the two pieces of flat glass is only 0.1-0.2mm, its heat insulation principle is to use the vacuum layer to isolate heat conduction, and there is no convection heat transfer, its heat transfer is mainly caused by radiation heat transfer.

The vacuum glass structure is shown in the figure below, it is composed of two pieces of flat glass, an array of supports, a perimeter sealing layer, the inner cavity of the two pieces of flat glass is pumped into a vacuum, in order to keep the interval between the glasses, a support array needs to be set between the two pieces of glass to withstand the atmospheric pressure of about 10 tons per square meter. The radiative heat transfer of vacuum glass is independent of the spacing between the two plates of glass, so the spacing between the two panes of glass can be very small, allowing for the production of highly compact insulated glass systems. At distances of 2-3m, these tiny supports are difficult to detect, so the impact of the supports on vacuum glass vision is negligible.

Vacuum glass has high sound insulation characteristics

The sound insulation performance of vacuum glass is better than that of traditional insulating glass and laminated glass, and vacuum glass avoids the disadvantages of insulating glass: there is a resonance trough at low frequency; It also avoids the shortcomings of laminated glass, which coincides with the shortcomings of moving from trough to low frequency. However, to improve the sound insulation performance of vacuum glass, it is not advisable to increase the thickness of the glass, but we can composite the vacuum glass with insulating or laminated glass, on the one hand, to improve the sound insulation performance, on the other hand, it will also make the vacuum glass have more advantages. For example, it is designed as sound insulation glass, sunshade sound insulation glass, safety sound insulation glass and other sound insulation glass with different characteristics according to the need.

Common quality problems with vacuum glass

(1) Poor support (different heights or side seals higher than the middle).

(2) Acquisition and maintenance of vacuum

When the vacuum degree is greater than 10Pa, that is, more than one ten-thousandth of an atmosphere, the U-value of vacuum glass is much greater than that of insulating glass, and the advantages of vacuum glass are lost.

(3) Choose a suitable low-E film

Some products or technologies based on vacuum glass

(1) Electrochromic vacuum glass.

Electrochromism refers to the phenomenon that causes a reversible oxidation or reduction reaction of a material due to a change in the polarity or strength of an applied electric field, resulting in a reversible change in its color.

(2) Aerogel vacuum glass.

The biggest problem in the current application and promotion of vacuum glass is the fragility and poor impact resistance caused by the stress concentration caused by the support point between the two pieces of glass. Since the production of vacuum glass is made of two pieces of flat glass with low melting point glass, a support is set between the two pieces of glass, and the gap is pumped into a vacuum. For this structure, due to the existence of atmospheric pressure difference, there will be obvious lasting stress and stress concentration of the support point inside the vacuum glass, resulting in the bending strength of the vacuum glass is not as good as 1/4 of the ordinary tempered glass, and its impact strength is also difficult to meet the requirements of the safety glass standard, so that the vacuum glass has potential fracture hazards in the application process, which greatly reduces the safety and reliability of the vacuum glass. If you want to solve this problem at the source, it is best not to use support points. The use of porous transparent materials for uniform support can greatly reduce the stress concentration.

Aerogel is a lightweight, nanoporous material with excellent thermal insulation, sound insulation, and vibration damping properties, while effectively penetrating the visible part of sunlight. The application of aerogel in building energy-saving glass has a good prospect, especially in the field of vacuum glass, which can further reduce the thermal conductivity of vacuum glass, and at the same time, the porous structure of aerogel can also reduce the heat transfer of residual gas in the vacuum chamber, so that the vacuum degree of the vacuum glass vacuum chamber can achieve a good thermal insulation effect at about l00Pa, eliminating the complex process of obtaining and maintaining the high vacuum of the existing vacuum glass. In addition, the traditional array support is replaced by aerogel, that is, the point support is replaced by a uniform surface support, which can evenly disperse the negative pressure force, thereby reducing or eliminating the stress concentration in the vacuum glass, and improving the overall strength and safety of the vacuum glass.