What is a hollow glass molecular sieve?
The most ideal desiccant for insulating glass is 3A molecular sieve. When 3A molecular sieve comes into contact with air, it only absorbs gaseous water molecules and some organic substances in the air, and does not absorb other components of the air.
Molecular sieve, also known as synthetic zeolite, is a silicate aluminosilicate microporous network crystalline material composed of SiO₂ and Al₂O₃ tetrahedrons. It has uniform pore sizes (about several angstroms) and an extremely large specific surface area.
Different types of molecular sieves have different pore sizes and shapes, which can be used to separate various molecules — this is the origin of the name "molecular sieve". Water molecules are highly polar molecules, so Type A molecular sieves have a high affinity for water and are often used as excellent adsorbents.
At present, the common specifications of 3A molecular sieves commonly used in insulating glass on the market are as follows:
- For machine-filled bent aluminum strips: molecular sieve products with a diameter of 0.5-0.9mm;
- For manually-filled cut aluminum strips: molecular sieve products with a diameter of 1.5-2.0mm;
- Other specifications by diameter: 1.0-1.5mm, 1.3-1.8mm, 2.0-2.5mm, etc.
However, in some insulating glass products currently on the market, the desiccant used is not 3A molecular sieve. Some manufacturers use 4A molecular sieve, or even Type B desiccant, as the desiccant in insulating glass, which will reduce the service life of insulating glass.
Although 4A molecular sieve also has a strong adsorption capacity for moisture, it also has a strong adsorption capacity for nitrogen and other inert gases in the air. Moreover, with the rise and fall of temperature, it will adsorb and release the gas in the insulating glass. With the changes of day and night temperature differences or seasonal alternations, the insulating glass is prone to distortion and breakage due to expansion and contraction, resulting in safety accidents. Therefore, in the production of insulating glass, it is strictly prohibited to use any molecular sieves other than 3A molecular sieve as the desiccant for insulating glass.