Application of Molecular Sieves in Insulated Glass
2019-04-03
Choosing the right type of molecular sieve plays an indispensable role in the quality and service life of insulated glass.
The sealed insulating glass was invented in 1865; initially, this type of insulating glass contained neither adsorbents nor organic sealants. However, it was only with the global energy shortage and the development of modern organic sealants and adsorbents that demand for insulating glass experienced tremendous growth. Thanks to its outstanding thermal insulation, soundproofing performance, as well as its bright and aesthetically pleasing characteristics, insulating glass has become increasingly widely used. China began developing insulating glass in 1964, and from its early handcraft production methods, it has now made significant progress in both quality and output. In particular over the past few years, insulating glass has been facing unprecedented opportunities for development.
Molecular sieves are ideal adsorbents for insulated glass. As a porous material, molecular sieves possess an exceptionally large internal surface area. They exhibit affinity for both water and solvents simultaneously. Decades of experience in insulated glass manufacturing have shown that sealants and adsorbents interact with each other and influence each other's performance. Through ongoing research and development, UOP has meticulously tailored each product in its MOLSIV series of molecular sieves specifically designed for insulated glass, ensuring that they deliver the precise performance characteristics required by every sealant system.
Molecular sieves play a remarkably important role in insulated glass units. They help prevent moisture condensation and frost formation on the inner surfaces of insulated glass units, inhibit solvent evaporation from sealants, reduce flexing under extreme climatic conditions, and protect against hydrocarbons present in the air—such as those found in paints, cleaning agents, and other solvents. During both manufacturing and use, water vapor from the atmosphere becomes trapped within the insulated glass unit. When ambient temperatures drop below the dew point of the gas inside the insulated glass unit, condensation occurs, resulting in the formation of condensation on the cold inner surface of the insulated glass unit.
How much desiccant is needed in insulated glass units? This question can be answered from three perspectives: experience, water balance, or equivalent requirement. Experience shows that most manufacturers fill the desiccant into two long sides or one long side and one short side of the unit. In many cases, this approach is sufficient. The water balance method, on the other hand, is a scientific approach that ensures there’s enough desiccant to remove any moisture that might seep into the insulated glass during manufacturing as well as throughout its service life. Of this desiccant, only a small portion is used for initial drying. A "relative humidity gradient" drives moisture into the interior of the insulated glass. Such a gradient arises when the humidity outside the unit exceeds the humidity inside. To calculate the amount of desiccant required over the entire service life of the insulated glass, a water balance analysis is necessary. This calculation requires knowledge of the rate at which moisture enters the unit, the designed service life of the insulated glass, and the highest dew point expected during the unit’s service life. The equivalent requirement refers to the minimum amount of desiccant needed per inch of insulated glass when testing the unit. In the United States, insulated glass manufacturers have already established guidelines for equivalent requirements, and many other countries are currently considering adopting similar standards.
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