The dew point of laminated hollow glass refers to the temperature below which the humidity of the air sealed in the air layer reaches saturation. The water vapor in the air layer will condense into liquid or solid water. The dew point rise of laminated hollow glass is caused by the outside water entering the air layer and can not be absorbed by the desiccant. The following three reasons can cause the dew point of laminated insulating glass to rise.
The existence of mechanical impurities in the sealant or the existence of discontinuous pores in the process of extrusion during the production of sealant. Under the action of pressure difference or concentration gradient inside and outside the air layer, the water in the air enters the air layer through gas flow or diffusion, so that the moisture content in the laminated hollow glass air layer increases. For the sealant of laminated hollow glass, the main diffuser is water in the air.
The main factors affecting the water vapor diffusion are the gas permeability coefficient (air tightness) of the polymer, the thickness of the adhesive layer and the water vapor partial pressure difference between inside and outside the air layer. Water vapor diffusion is the main reason of failure of laminated hollow glass.
The effective adsorption capacity of desiccant is low. The desiccant sealed in the air layer of laminated hollow glass has two main functions: it is to absorb the water sealed in the air during production, so that the laminated insulating glass has a qualified initial dew point. The second is the continuous adsorption from the environment through the rubber layer to the air in the middle of the water, keep the laminated hollow glass has always met the requirements of the use of dew point, so the desiccant should have a strong adsorption capacity. If the adsorption capacity of desiccant is poor, it can not effectively absorb the water in the air layer through diffusion, which will lead to the accumulation of water in the air, the increase of water pressure, and the rise of the dew point of laminated hollow glass.