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Discussion on quality status and selection control of silicone sealant for insulating glass.

1. Introduction

With the increasingly fierce competition in the glass deep processing industry, various manufacturers have tried their best to seek development to remain invincible in the fierce competition. In the market game, companies that have a certain sense of social responsibility and hope that the company can continue to develop healthily, in addition to actively doing a good job in market development, continue to tap their internal potential, work hard on their management, and strengthen internal management to deal with market competition. By introducing talents, improving equipment, improving labor efficiency, improving product grade and quality, and developing differentiated products to win the trust and orders of customers, not only has not been affected by the market, but even bucked the trend, and achieved better performance and development. The prospects are broad. Some enterprises, to cope with the harsh market environment of 7%, lost themselves in the fierce competition environment. Instead of seeking benefits from the front, they extended labor hours, reduced quality requirements, cut corners, and used inferior raw materials. To reduce costs, the market has formed an impact state of "bad money drives out good money". The entire glass deep processing market has fallen into a harsh competitive environment. A large number of defective products are flooding the market, and a large number of constructions will break out shortly. 

According to statistics, from January to December 2021, the cumulative year-on-year growth rate of insulating glass production worldwide was 9.4%. Insulating glass is an important architectural glass product with rapid growth and is mainly used in mid-to-high-end buildings to ensure hollow The quality of glass products has a huge impact on the functionality of building doors and windows. The silicone sealant for insulating glass to be discussed is a typical raw material in this unfavorable competitive environment. Jinan LIJIANG Glass visited many glass deep-processing enterprises of different sizes in various places. Many manufacturers are using inferior sealants. These inferior sealants The quality of the glue is worrying. After some sealants are used on insulating glass products to dry and solidify, they will fall off with a single button with a finger.

2. Silicone sealant quality requirements

2.1 Classification and characteristics of sealant

The main types of sealants for hollowing are butyl rubber, polysulfide rubber, silicone rubber, and polyurethane sealant. At present, the production process of insulating glass is mainly based on double sealing. In the double sealing process, butyl rubber is used for the first sealing. The gas permeability and water vapor permeability of butyl rubber are the smallest, which mainly prevents water vapor penetration. Over-action; polysulfide sealant, silicone sealant, or polyurethane sealant for the second seal, polysulfide sealant or silicone sealant has better bonding performance, the main function is the bonding performance, and it also acts as an auxiliary seal The role of polyurethane glue is also used as a secondary sealant, but the amount is small. The main sealing methods include applying two layers of sealant with an automatic sealing robot machine or applying a second layer of sealant with a manual rotary gluing equipment.

Compared with silicone rubber, polysulfide rubber has better oil resistance, solvent resistance, sealing performance, and better stability. It is not easy to be incompatible with glass, butyl rubber, desiccant, and aluminum strips. It is an ideal insulating glass sealing material, which is beneficial to the quality assurance of insulating glass. Silicone glue is easy to react with other materials and affects the product quality and service life of the insulating glass, but silicone glue has become the main material for insulating glass sealing due to its excellent adhesion, aging resistance, and UV resistance. The curtain wall glass with a hidden frame and semi-hidden frame has advantages that other glues cannot match. At present, the second sealant used in the market is mainly polysulfide rubber and silicone rubber. However, due to the high price of polysulfide rubber, it has a strong irritating odor in use, which makes it difficult for many production operators. If they are willing to use it, companies tend to choose silicone rubber mainly from the perspective of reducing costs, so the use of silicone rubber has occupied a dominant position.

Figure 1 The polysulfide rubber 1

Figure 1 The insulating glass polysulfide rubber 1

2.2 Silicone sealant quality requirements

In comparison, silicone rubber has the properties of structure, aging resistance, and UV resistance, and is more adaptable to the environment, but its weakness is the high water vapor transmission rate. The performance of the insulating glass exposed to the atmosphere was used in the test. The results showed that the test results under the same conditions were: the polysulfide type sample was exposed to the sun for 3 years, the permeated water quality was 0.35g, 5 years was 0.55g, and the silicone type was exposed to the sun for 3 years. . The type of external sealant is a significant factor affecting the permeability of insulating glass. The water permeability index of insulating glass bonded by silicone sealant is much higher than that of polysulfide glue, and the durable service life of the two is nearly doubled. Silicone glue has advantages in price and bonding performance, but its high water vapor transmission rate is also its main problem. When using silicone glue as insulating glass sealing material, it is even more necessary to ensure the quality of the sealant to meet the application requirements.

Generally speaking, the quality of the silicone sealant should have good adhesion, certain elasticity, and elastic recovery ability, anti-ultraviolet aging performance, low water vapor permeability, and the sealant should be fine and fewer impurities after construction, which is convenient for production, operation, and construction. , The performance of the sealant meets the requirements of relevant standards, the product quality is stable and reliable, and the compatibility of the sealant with butyl rubber, desiccant, and other materials must be ensured. In the selection of sealants, following the principle of high quality and low price is an important indicator for selection and reference. For the selected sealants, relevant performance tests can be carried out to verify the product quality. Only by constantly summing up the experience in the work can the quality of good sealants be selected.

2.3 Quality status of silicone sealant

Silicone sealants are usually high molecular polymers, mainly based on hydroxyl-terminated polysiloxane as the matrix material, and composed of vulcanizing agents, catalysts, plasticizers, reinforcing fillers, and other auxiliary agents. Its matrix material needs to meet the corresponding requirements of the proportion or more.

The competition in the sealant market is very fierce. To reduce costs, some manufacturers use a large number of fillers instead of matrix materials, which causes the quality of the sealant to fail to meet the requirements, resulting in problems such as decreased adhesion, poor elasticity, poor sealing performance, and poor weather resistance of the glue. , thus seriously affecting the quality of insulating glass products. In particular, a large amount of cheap white oil is added as a plasticizer instead of dimethyl silicone oil, which may dissolve the butyl rubber, causing the "tears" phenomenon of the insulating glass. As soon as the day appeared, the butyl sealant failed or was affected, and the quality problems of the insulating glass products followed.

A few days ago, there has also been a market where manufacturers can adjust and produce sealants of different qualities according to customer price requirements. The production process control is relatively chaotic and the quality is difficult to guarantee. The price of silicone sealant with quality assurance is about 850~1000usd per barrel, while the market is flooded with inferior silicone rubber with the price of about 450usd per barrel, and the price difference is almost 1 time. Where there is demand, there is a market. An enterprise chooses inferior sealants to reduce costs. The market is flooded with low-priced and inferior sealants, which will inevitably affect the quality of insulating glass products.

2.4 The use of silicone sealant

As a chemical material, the quality control and inspection of sealant is a big difficulty for glass processing enterprises, especially many small and medium-sized enterprises. Weak ability, do not know how to evaluate and judge the quality of sealant. Jinan LIJIANG Glass has interviewed some glass deep-processing enterprises on the control of hollow sealants. Many enterprises do not take any means to control them, which is difficult to ensure product quality. Judging criteria, what to buy cheaply, less consideration for product quality.

As the saying goes, where there is demand, there is a market. It is this idea of low price control that fuels the production and development of inferior sealants. Jinan LIJIANG Glass has investigated some sealant manufacturers. The boss is responsible for the market and all operational control. The production staff is responsible for everything from production to delivery.

3. Suggestions to ensure that the quality of the sealant meets the production requirements of insulating glass

To ensure that the quality of insulating glass products meets the requirements, enterprises need to work hard on awareness and control.

First, enterprises need to establish a correct product quality concept, assume corresponding social responsibilities, and ensure that the purchased sealant meets the requirements, and cannot blindly pursue low prices and ignore quality. This is the fundamental control thinking and means;

Second, the purchase of sealant needs to choose enterprises with a certain scale, reputation, and brand protection. Usually, these enterprises have strong quality control capabilities and stable product quality, which can ensure that the sealant meets the requirements of insulating glass production;

The third is that the sealant purchased into the factory needs to undergo relevant performance and compatibility tests to ensure that the relevant performance has been inspected and verified, and the sealant that meets the requirements can be put into production;

The fourth is to strengthen the study and exchange of relevant product knowledge and skills, to ensure that production operations and product quality control meet the specifications, and to avoid product problems caused by improper operation.

Production control cannot be ignored to ensure the quality of insulating glass products. For insulating glass production control, the international industry standard "Technical Regulations for Insulating Glass Production" puts forward corresponding control specifications for the production control of insulating glass, and the control is carried out according to the requirements of the regulations, and the product quality is average. can be better guaranteed.

Figure 2 The insulating glass coated with secondary glue on site 1

Figure 2 The insulating glass coated with secondary glue on site 1

4. Conclusion

As the main raw material for insulating glass production, silicone sealant has a great impact on the quality of insulating glass products. Enterprises engaged in insulating glass production should choose to use products that meet the requirements from the perspective of fulfilling social responsibilities and considering the long-term development of the enterprise. sealant, and at the same time do a good job in the production process control to ensure the quality of insulating glass products. 

To choose the higher quality of insulating glass silicone sealant, could promote the healthy development of the glass deep processing industry, promote the continuous advancement of energy conservation and emission reduction, and contribute industry wisdom and strength to achieve sustainable development and build a resource-saving and environment-friendly society.

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