Insulated glass desiccants are typically made from 3A molecular sieves (Angstrom, 1? = 0.1 nanometer), which are extracted from bauxite and synthesized with NaOH, Na2SiO3, KOH, Ca(OH)2, and other materials. These sieves are processed through granulation, high-temperature calcination, and sieving. They feature adsorption at room temperature and desorption at high temperatures, and are commonly used for drying gases and liquids. The desiccant can simultaneously absorb moisture and residual organic compounds in insulated glass, ensuring the glass remains clear and transparent even at low temperatures. It also helps reduce the internal and external pressure differences caused by significant temperature fluctuations, preventing distortion or breakage due to expansion or contraction, and greatly extending the lifespan of the insulated glass.

• The adsorption rate is not affected by low temperatures, maintaining the same adsorption capacity at 0°C or below. (At low or high temperatures, silica gel and mineral desiccants show a significant decrease in adsorption, negatively impacting the dew point of the insulated glass.)
• The adsorption rate is not significantly influenced by humidity, and the desiccant retains good adsorption ability even in environments with relative humidity below 20%. (In lower humidity conditions, silica gel and mineral desiccants experience a marked reduction in adsorption.)
• Molecular sieves can selectively adsorb substances smaller than their molecular size, including water molecules.
• Molecular sieves can adsorb both gaseous and liquid water.
• Molecular sieves are highly durable, stable, and do not crack, shed powder, expand, or deform upon contact with water.

Molecular sieves are generally classified based on their chemical composition and pore size:

• 3A Molecular Sieve: Pore size is approximately 3? (0.3 nanometers), primarily used for adsorbing water while excluding larger molecules (such as methanol, ethanol, etc.).
• 4A Molecular Sieve: Pore size is approximately 4? (0.4 nanometers), can adsorb water, methanol, ethanol, and other smaller molecules.
• 5A Molecular Sieve: Pore size is approximately 5? (0.5 nanometers), suitable for adsorbing slightly larger molecules like n-hexane.
• 13X Molecular Sieve: Pore size is approximately 10? (1 nanometer), ideal for adsorbing larger gas molecules such as CO2 and hydrogen sulfide.

• The 3A molecular sieve exhibits selective adsorption, only adsorbing water while excluding oxygen and nitrogen in the air. This is because the primary function of the desiccant inside the insulated glass is to absorb moisture, and water molecules have a diameter of about 2.6?. In comparison, nitrogen and oxygen molecules have larger diameters, about 3.6? and 3.4?, respectively. Therefore, 3A molecular sieves can effectively absorb water while preventing the adsorption of other gases. Other desiccants, such as 4A molecular sieves, not only adsorb water but also attract oxygen, nitrogen, and CO2, which can lead to internal pressure imbalances as the external temperature fluctuates, potentially damaging the glass’s shape and reducing its lifespan.
• Additionally, 3A molecular sieves are mildly alkaline, with a pH value of 10.5, which prevents any harm to the aluminum spacer in insulated glass. In contrast, some desiccants, like calcium chloride, can be corrosive and, as they absorb more moisture, could damage spacers and seals, increasing the risk of failure in insulated glass. 3A molecular sieves avoid such issues, ensuring the safe use of insulated glass.
• 3A molecular sieves also have excellent moisture absorption performance, with an absorption rate of up to 0.04g/s and at least 20% absorption capacity. This high efficiency ensures that the insulated glass can maintain very low relative humidity over extended periods, contributing to the glass’s long-lasting durability. In contrast, conventional desiccants absorb moisture more slowly, and under normal temperature or higher (≥40°C), they may undergo hydrolysis, which could harm the transparency of the glass.
• Under normal conditions, 3A molecular sieves do not undergo hydrolysis because their adsorption of water is primarily based on van der Waals forces, which are intermolecular forces. On a microscopic level, the internal pore structure of the sieve reaches an electrostatic equilibrium when water molecules enter. The polarity of the water molecules encourages them to split into hydrogen and hydroxide ions, which interact with the sieve’s internal electrostatic field, restoring balance and releasing energy (manifesting as a temperature increase). However, it’s important to note that these changes are purely physical and do not involve any chemical reactions. Therefore, under normal conditions, the adsorption of water by 3A molecular sieves is stable and does not result in hydrolysis.

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