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Selection and Production Control of Raw Materials for Low-E Coated Insulating Glass


According to statistics, the energy lost through windows in buildings accounts for more than 30% of the energy consumed by buildings. With the development of the national economy, the country has become more and more demanding on issues such as environment and energy conservation. Since the implementation of the "Design Standards for Energy Conservation in Residential Buildings", the use of traditional single-panel glass is far from enough to achieve the goal of 65% energy conservation in new residential buildings. of. The U value of an ordinary single-layer glass window is about 6.0W/m² ·K, the U value of a single-frame double glass steel-plastic composite window is about 3.5 W/m² ·K, and the U value of the window should reach 2.5 W/m² ·K or less It is necessary to use Low-E hollow glass. A lot of practice at home and abroad has also proved that improving the thermal insulation performance of the building envelope, especially improving the thermal insulation performance of the windows is the most economical and effective way to prevent the heat loss of the building. The energy-saving low-emissivity coated hollow glass that focuses on heating in winter and takes into account air conditioning and cooling in summer is an inevitable trend of development. With the large-scale application of energy-saving insulating glass, its quality issue has been put on the agenda. 

Two main factors are affecting the quality of insulating glass: 

(1) the selection of raw materials; 

(2) the quality control of the production process.  

Figure 1 The structure of insulating glass units

Figure 1 The structure of insulating glass units

1. Selection of insulating glass raw materials   

At present, there are mainly three types of insulating glass in the marketing of glass processing industry : 

(1) Aluminum groove single-channel seal; 

(2) Aluminum groove double-channel seal; 

(3) Composite sealant strip type insulating glass. 

Channel aluminum single-channel seal, because of its poor sealing performance, easy to enter the moisture, causing glass condensation, frost, short service life, so this kind of insulating glass is gradually eliminated. The raw materials of the latter two types of insulating glass are mainly: glass, aluminum strips, gussets, butyl rubber, two-component polysulfide rubber or silicone rubber, desiccant, and composite sealing tape. The quality of raw materials will directly affect the quality and service life of the insulating glass. The precautions for the selection of raw materials are briefly described as follows: It is a product in which two or more pieces of glass are effectively supported and evenly separated and bonded and sealed to form a dry gas space between the glass layers.  

1.1 Selection of glass  

The original glass can be float glass, laminated glass, tempered glass or semi-tempered glass, coated glass, colored glass, patterned glass, etc.  

1.2 Selection of sealant

1.2.1 Butyl rubber: 

Butyl rubber is the first seal of aluminum strip type insulating glass. It is a hot melt adhesive with a low water vapor transmission rate and high viscosity. It is the side of the aluminum strip. The most effective barrier against water vapor between the glass and the glass, but it needs to be heated, pressurized, and extrusion coated on both sides of the aluminum strip by a special machine. At present, there are many domestic butyl rubber brands, but the properties of each rubber such as heating temperature and pressure are different, which requires users to choose the best one.  

1.2.2 Polysulfide glue: 

Polysulfide glue is currently the largest amount of insulating glass sealant, it has good oil resistance, solvent resistance, and sealing properties. Polysulfide adhesives must have metal oxides as curing agents to polymerize, generally two-component, the ratio of the two components is about 1:10, machine coating, the manual coating can be used. Selection requirements: the color difference between the two components is clear; it has good fluidity and curing flexibility; strong anti-ultraviolet ability; the validity period is more than half a year. 

1.2.3 Silicone sealant: 

It has structural properties, anti-aging properties, and anti-ultraviolet properties, but its fatal weakness is its high water vapor transmission rate. It is suitable for places with strong sunlight and a poor environment. At the same time, butyl rubber must be used for the first seal. It shall comply with relevant international industry standards for insulating glass sealants. Ordinary silicone rubber is used in large quantities to make insulating glass, which may cause oil leakage. This is caused by the migration of silicone rubber plasticizers after some time. Silicone oil will melt the first sealing butyl rubber and cause butyl Glue is flowing, which affects the appearance and causes the hollow glass to fail. Attention should be paid when selecting it.

Figure 2 The selection of insulating glass sealant 1

Figure 2 The selection of insulating glass sealant 1 

1.3 Selection of aluminum spacer frame and gusset

The thickness of the aluminum strip should be between 0.3 and 0.35mm, the thickness should be uniform, and the vent holes should be evenly distributed. The aluminum bar needs to be anodic oxidation treatment or decontamination treatment and needs to be bent. It is necessary to select high-quality and high-grade products to increase the utilization rate of the aluminum bar.   

Gusset size should be selected, and the surface should be wiped clean.  

1.4 Desiccant   

There are mainly three kinds of common desiccants for insulating glass: 

1. The absorbing capacity for volatiles is better; 

2. The adsorbing capacity for inert gas is the lowest; 

3. Ordinary molecular sieves. 

Users should choose the appropriate molecular sieve according to their actual situation, and the molecular sieve should have the appropriate particle size (1-1.5mm) and hardness. In addition, the environment where the molecular sieve is used should be dry, and the filled molecules should be used within one hour to ensure the quality of the hollow glass.  

1.5 compound sealing tape  

The rubber strip is a raw material for insulating glass that integrates support frame (wave-shaped aluminum tape/stainless steel tape), sealing (butyl rubber), and drying (desiccant). Its biggest advantages are simple operation process, less waste of raw materials, fewer personnel, low management costs, and a good operating environment. The disadvantage is that the rubber strip is slow to absorb moisture and must have special equipment. At present, the price of the rubber strip is limited by the output. The selection of the composite sealing strip should consider the smooth surface, the quality of the aluminum strip, the content of the glue, and the moderate viscosity.  

Figure 3 The insulating glass composite sealing strip 1

Figure 3 The insulating glass composite sealing strip 1

2. Low-emissivity insulating glass production process control 

Last year, the glass production standardization committees of some developed countries regulated the control of the production process of insulating glass and will form a formal industry production standard. For manufacturers, standardizing the control of the production process of insulating glass and strengthening training on operation details are urgent. How to ensure and improve the quality of insulating glass products will become effective competitiveness for manufacturers to enhance their product brands and occupy the market. This section analyzes the main factors that affect the quality of the insulating glass production process. It is hoped that the relevant production control personnel can learn from and take effective measures in time to ensure the appearance and performance quality of the insulating glass products.  

The process flow of insulating glass includes the production processes of sheet loading, film removal, washing and drying, frame loading, sheet bonding, sealing glue, sheet loading, and additional bending, molecular sieve filling, and butyl coating. The production of insulating glass can be completed by Jinan LIJIANG Glass fully automated insulating glass production line equipment. The technological process is complicated, and qualified products depend on strict control of every production link. 

2.1 Glass cutting material  

The original piece of glass must meet the requirements of the relevant standards and can be used only after passing the inspection. Glass cutting can be done by hand or machine, but it should meet the size requirements. During the operation of this process, workers should always pay attention to the glass surface without scratches, uniform internal quality, and no obvious defects such as bubbles and slag inclusions.  

2.2 Glass washing and drying  

The glass washing and drying must use the machine washing method. The glass must be inspected for scratches before washing. To ensure the adhesion of the sealant and the glass, it is best to use deionized water. The washed glass must pass the light inspection to check whether there are water droplets, water stains, and other stains on the surface of the glass. If there are water droplets, water stains, and other stains, the operating speed of the machine, heating temperature, air volume, and brush gap must be checked. Adjust until the effect is intact. After washing, the glass should be assembled into hollow glass within 1 hour. In addition, ensure that there is no friction between the glass and the glass. It is best to have a storage cart for semi-finished glass to separate the glass sheet from the sheet. After the sealed hollow glass is placed on the A-frame, the overall appearance quality of the hollow glass should be checked again: the uniformity of the hollow rubber mixing, whether there is hollow rubber, bubble rubber, or old rubber; whether the joint between the hollow rubber and butyl rubber is good, whether there is a dotted line, etc. After the insulated glass glue is cured for three hours, check whether its surface dryness is uniform, and after eight hours, check whether the curing degree is qualified.The correct placement of the Low-E insulating glass will also affect the final quality of the insulating glass. Whether it is in production, transportation, or storage at the construction site, the design requirements of the stacking rack must take into account the characteristics of the insulating glass, and the stacking rack should be a certain slope. However, the bottom plane and the sides should always be kept at 90 degrees, to ensure that the two glass-bottom edges of the insulating glass can be placed vertically on the stacking rack. In addition, please pay attention not to stain the bottom of the glass with oil, lime, and other solvents, because they will corrode the second sealant of the insulating glass to varying degrees, thereby affecting the sealing performance of the insulating glass.  

Figure 4 The producing processing of Jinan LIJIANG Glass Insualting glass production line equipment

Figure 4 The producing processing of Jinan LIJIANG Glass Insualting glass production line equipment

3. Summary   

The quality of insulating glass is guaranteed, one is the quality of the raw material itself, and the other is the strict and standardized quality control of the production process. Details determine success or failure, that is, in each processing link, close attention should be paid to factors that may affect the appearance of the material and the performance of the hollow structure, to take effective measures to avoid operational errors and improper operations. Only in this way, the quality of insulated glass products can be guaranteed. Advanced production equipment, strict product quality standards, and a standardized management system should produce first-class products.   

The quality of low-radiation insulating glass is related to the key to building energy saving. If it fails, it will not be able to save energy. Generally speaking, we should continue to improve the processing technology of low-radiation insulating glass, strive to improve the technical level and product quality, and promote the development of low-radiation insulating glass to a higher, newer, and stronger direction.

For more information about Jinan LIJIANG Glass insulating glass processing equipment and insulating glass processing accessories, please click here to learn more. 

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