Environmental requirements and development trends of silicone sealants for building doors and windows

The energy-saving and environmental protection of building doors and windows will directly affect the user's use effect. As one of the important materials for waterproof and sealing doors and windows, silicone sealant plays a decisive role in the use of doors and windows. This article analyzes the energy-saving and environmental protection performance and application requirements of silicone sealant for doors and windows and discusses the current development of the silicone sealant industry for building doors and windows, to guide the healthy development of the door and window sealant industry in the future.

With the rapid economic development, people’s living standards continue to improve, and the requirements for the built environment are getting higher and higher. In addition to satisfying the most basic use functions, more attention is paid to the quality and aesthetics of decoration, and energy conservation and environmental protection are also beginning to be paid attention. 

As an important part of the building, doors and windows are also the outer protective structure of the building. To increase the lighting and ventilation area of modern buildings, the area of doors and windows of the building is getting larger and larger. In the past, the industry focused on energy conservation, environmental protection, and energy efficiency of doors and windows. Most of the focus was on how to choose insulating glass with lower thermal conductivity, how to improve the inert gas retention rate of inflatable insulating glass, how to design the cavity structure of the profile to reduce heat conduction, and to choose glue injection Thermal insulation or nylon insulation strips, etc., and the selection of silicone sealants, especially environmental performance requirements, has not attracted enough attention.

^{The silicone sealants sealing for building doors and windows 1}

The weatherproof and waterproof sealing of doors and windows is the same as the curtain wall, which is a systematic project, including the sealing between the window frame and the glass, and the sealing between the outer wall and the door frame and window frame. The design and use of energy-saving doors and windows in modern buildings is the key to energy conservation and environmental protection in green buildings, but the quality of edge sealing is the key to whether the system as a whole can exert its application effect. Therefore, how to choose silicone sealant as the application of door and window system is not for us. Ignored the point. The energy loss caused by the failure of the seal is far more than the saving of choosing better glass and profiles. No one can imagine how to talk about building energy conservation and environmental protection in a leaky building. This article introduces the environmental protection requirements, development trends, and selection principles of silicone sealants for building doors and windows on the environmental performance standards of silicone sealants on building doors and windows, to help the majority of door and window users choose environmentally friendly, qualified, and high-quality sealants. Ensure the longevity of the building's waterproof seal.

1. The development status of building decoration materials

With the continuous improvement of living standards, people's taste in life has also been continuously improved. Concerning environmental issues that have become more frequent in recent years, people have become more and more aware of health, energy conservation, and environmental protection. However, even in such a market atmosphere, toxic and harmful decorative materials are still sold in large quantities by illegal vendors. This means of making money regardless of the safety of others has destroyed the family happiness of countless people. For example, almost all synthetic boards contain formaldehyde. Even wooden furniture also contains trace formaldehyde. In addition, in addition to furniture and marble window sills, there may be radioactive materials that can cause harm to the human body. Therefore, in the construction of building decoration, we must use energy-saving and environmentally-friendly green decoration materials to better protect the environment and ensure the health of residents.

2. Environmental protection requirements for building doors and windows industry

With the successive promulgation and implementation of my country's building energy conservation and environmental protection standards, the construction industry has actively responded to the trend of energy conservation and environmental protection, using materials with environmental protection properties in buildings, and contributing to the realization of a win-win situation for the social and economic benefits of buildings. The topic of household pollution has always been a topic of more concern to the public, but there are many cases of diseases caused by household pollution. Door and window products are the first layer of protection for home safety. Consumers’ demand for environmental protection of door and window products is increasing rapidly. In this context, a large number of energy-saving and environmentally friendly doors and windows such as aluminum alloy doors and windows, broken bridge aluminum alloy doors and windows, aluminum-plastic composite doors, and windows, etc. Products continue to emerge.

Silicone sealant is widely used in the door and window industry for bonding and sealing between glass and window frames, doors and windows, and walls because of its excellent weathering resistance and environmental protection characteristics. People often have a misunderstanding in real life. When it comes to glue, they think of formaldehyde and toluene, which are unclear to the human body. But silicone sealant belongs to the main body adhesive, and its green environmental protection is mainly reflected in the fact that it does not contain toxic and harmful substances such as formaldehyde and toluene, and has a low total volatile organic content, which meets the functional requirements of modern green buildings.

Judging from the comparison of the standard content of the above four commonly used silicone sealants for the detection of hazardous substances limit requirements, for silicone sealants, the standard testing content does not involve the detection of formaldehyde, toluene, benzene, xylene, and toluene diisocyanate. Once again confirmed that silicone sealant does not contain formaldehyde and benzene harmful substances. At the same time, from the analysis of the time axis, the total volatile organic content of silicone sealants shows a trend that as the standards formulated are newer and more stringent, the volatile matter in the curing process of silicone sealants is lower; The overall development trend of the industry is to require more energy-saving and environmental protection.

3. The curing mechanism of silicone sealant

Silicone sealant is a paste made of hydroxyl-terminated polydimethylsiloxane as the basic raw material, supplemented by cross-linking agents, fillers, plasticizers, coupling agents, catalysts, and other additives in a vacuum state. , In terms of product form, it is divided into one-component and two-component. The single-component sealant is simple to use. It does not need to be weighed and mixed before construction. After construction, it is cross-linked and cured with the help of moisture in the air or low-temperature heat activation; Two-component sealant, mixed in proportion before use, cross-linking and curing with the help of the cross-linking agent. Because the polymer molecule has a siloxane chemical structure on the main chain, it is called a silicone sealant.

^{Table 2 List of main components of silicone sealant}

At present, the common silicone sealants for doors and windows on the market are mainly single-component. Single-component silicone sealants can be divided into two types: acid glue and neutral glue according to the small molecules released during the reaction. The coupling agent triacetoxysilane participates in the reaction to release acetic acid, which is corrosive to metal materials to a certain extent and will produce a pungent odor at the same time. Because it is corrosive to metal materials, it is mainly used for general bonding between glass and other building materials. The neutral glue avoids the shortcomings of acid glue corroding metal materials, so it has a wider range of applications. When the dealcoholized neutral glue is cured, the crosslinking agent trimethoxysilane will participate in the reaction and release alcoholic substances, such as methanol, Ethanol, etc.; when the dioxide neutral glue is cured, it will release oxime substances, such as methyl ethyl ketoxime, etc.

At the same time, as people continue to pay attention to environmental protection and health, the health index of silicone sealants during interior decoration has also become an important evaluation standard; many people have such doubts about whether the sealant will cause harm to the human body. At present, in the door and window industry, because the acid sealant has a large pungent odor, although it will not cause harm to the human body, it will affect the comfort of use. Therefore, the common sealant used for doors and windows in recent years is a one-component dealcoholization or oxime room temperature vulcanization silicone sealant, collectively referred to as neutral glue. Neutral glue will release small organic molecules, mainly alcohols or oximes, during the curing process. Under standard curing conditions, it usually takes 3-5 days to fully cure. After the released small molecules are completely volatilized, they will no longer have any odor. The phenomenon.

4. Current status of silicone sealant industry

At present, domestic silicone sealant brands are dominated by domestic and foreign first-line brands, and other brands co-exist in the form of joint development. The first-line brands mainly include foreign high-end brands: Tao Xi (formerly Dow Corning), WACKER, GE, Shin-Etsu, etc. In addition, there are nearly a thousand sealant manufacturers all over the world, and all levels of sealants are available in the entire industry. Occupying different shares has also led to a relatively chaotic sealant market and uneven product quality.

4.1 The basic organic content of the sealant is low

The main components of silicone sealant include 107 glue (α, ω-dihydroxy polydimethylsiloxane), 201 methyl silicone oil, nano calcium carbonate, white carbon black, curing agent, etc., which are formulated in different proportions. And mixed according to the corresponding preparation process. Usually, 107 glue is a basic polymer in silicone glue, and its content directly determines the aging performance of the sealant for long-term use and also determines the cost of the sealant. Many manufacturers in the industry will reduce the content of 107 in the sealant to reduce the cost of product raw materials, so the quality of the sealant is reduced, and the weather resistance and durability are reduced. Low-priced silicone sealants are prone to hardening, cracking, and debonding during use, leading to later renovation and rectification, resulting in more waste of resources, and it is not suitable for sealing doors and windows that require environmental protection.

4.2 The sealant has high mineral oil content

To reduce the manufacturing cost of the sealant, some manufacturers will add mineral oil to the sealant instead of silicone oil and other ingredients. This kind of mineral oil will cause the sealant’s aging resistance to drop sharply. Excessive addition may even cause hollow glass after use. "Tears" and other phenomena. At the same time, due to the strong volatility of mineral oil, over time, the volatilization of mineral oil will cause the sealant to have a big smell after use, affect the environmental performance of the sealant, and cause the sealant to fail to meet the corresponding green environmental protection standards. Even some manufacturers add cheap, unidentified organic materials into the sealant, which has extremely poor environmental performance and seriously affects human health.

4.3 Product application chaos

According to different application parts, sealants can be divided into building curtain wall joint sealants, glass curtain wall structure bonding sealants, door and window joint sealants, etc. During the selection process of building seal materials, customers will save material costs. Consider the type of glue used purely from the perspective of price. For example, applying door and window glue to curtain wall joint sealing, door, and window joint sealing using an inelastic sealant with extremely low displacement capacity, etc., will easily cause the sealing of building joints to fail over time. Water leakage does not meet the requirements of energy conservation and environmental protection. Recommendations for the application of products in reasonable parts can be suitable for suitable materials and meet the long-term sealing requirements of energy-saving and environmentally-friendly buildings.

5. The development trend of silicone sealants

Energy-saving doors and windows, system doors and windows, smart doors and windows, and passive doors and windows are a trend in the development of modern building doors and windows. The most important feature is to increase the lighting and ventilation area or express the characteristics of modern buildings, and the wind pressure resistance and water tightness of doors and windows And airtightness have become one of the concerns. At the same time, the evaluation of green buildings also puts forward higher index requirements for the selection of materials. In addition to meeting the product standard index requirements, the sealant should also have the following characteristics.

5.1 Fast curing

With modern production rhythms and control of space and time costs occupied by the maintenance and transportation of finished doors and windows, more and more door and window manufacturers are requesting that silicone sealants have a shorter surface drying time and a faster deep curing speed, thereby improving production efficiency.

5.2 Broad adhesion

The bonding mechanism of silicone sealant is to form a permanent bond through a chemical reaction with the surface of the material. However, there are many types of surface treatments for conventional aluminum frames used in modern doors and windows. In addition, various plastics and new materials are emerging in an endless stream. It is required that silicone sealants have good and extensive adhesion to various materials to ensure a good waterproof sealing effect.

5.3 Environmental performance

Silicone sealant itself is very environmentally friendly, and the quality of the product can be distinguished through corresponding standards and methods. You can also choose to conduct a green evaluation of the product through a third-party authoritative organization.

5.4 Green Evaluation System of Silicone Sealant Factory

The current green environmental protection not only refers to the non-toxic and harmless products themselves but also needs to be traced to the manufacturing process of the products. From resource extraction, raw material production and transportation, energy production, product production to delivery, a systematic evaluation is carried out. Paying attention to the energy consumption of raw materials and the transportation process of various materials will also affect the environmental performance of the silicone sealant's life cycle.

^{The silicone sealants sealing for building doors and windows 2}

6. Concluding remarks

Silicone sealant only accounts for 3 to 5% of the cost of the entire building's doors and windows, but its quality will directly affect the quality and energy-saving effect of the entire building project. In addition to meeting the basic performance indicators, the selection of silicone sealants should also implement corresponding environmental protection standards according to actual application requirements. Fast curing, extensive adhesion, environmental performance, and green evaluation system for production plants are the future development trends of silicone sealants for building doors and windows.