With the continuous improvement of the quality of life, people have clear requirements for the quality and performance of residential buildings. The energy-saving performance, safety performance, sound insulation and noise reduction, sun protection, comfort, more and more attention has been paid to durability. When consumers buy building doors and windows products, they not only require the beauty of the products, but also pay more and more attention to the excellent performance.
With the continuous improvement of the quality of life, people have clear requirements for the quality and performance of residential buildings. The energy-saving performance, safety performance, sound insulation and noise reduction, sun protection, comfort, more and more attention has been paid to durability. When consumers buy building doors and windows products, they not only require the beauty of the products, but also pay more and more attention to the excellent performance.
Although sealant is only an auxiliary material in the manufacturing process of doors and windows, which accounts for a small proportion of the cost, it plays a very important role in the performance of doors and windows, especially in watertight, airtight, heat preservation, sound insulation plays a vital role.
If the sealant has quality problems, it will lead to water leakage, air leakage and other problems, which will seriously affect the air tightness and water tightness of doors and windows (the entry "water tightness" is provided by industry Encyclopedia); therefore, special attention should be paid to the correct selection of sealant, which should not be careless and perfunctory, so as not to prevent sealant from failing to be applied, resulting in the performance of doors and windows not meeting the expected requirements.
1. Standard introduction of sealant for doors and windows
how to correctly select sealant for doors and windows? First of all, we need to choose products that meet the standards. The author first introduces several common standards of sealant for doors and windows.
1.1 silicone sealant for building
according to the displacement capacity, it is divided into 25 and 20 levels, and the low and high modes are distinguished respectively according to the tensile modulus. This standard specifies the product classification, requirements, test methods and inspection rules of silicone sealant for embedded glass and building joints. GB/T 14683-2003 sealant grades are as follows:
GB/T 14683-2003 is applicable to cold curing cold setting single-component silicone sealant. Products conforming to this standard are completely applicable to the processing, manufacture and installation of doors and windows.
1.2 sealant for concrete building joints
JC/T881-2001 was formulated earlier, and this standard is not equivalent to the quality requirements of class F products in ISO11600:1993 "building structure-sealing materials-classification and requirements. Therefore, JC/T881-2001 is basically consistent with class F classification and requirements in ISO11600. According to the displacement capacity, it is divided into 25 levels, 20 levels, 12.5 levels and 7.5p levels, of which 25 levels, grade 20 distinguishes low and high modes respectively according to tensile modulus, and grade 12.5 is divided into elasticity according to elastic recovery rate (entry "elasticity" is provided by industry Encyclopedia)(E) and plasticity (P).
This standard specifies the classification, technical requirements, test methods and inspection rules of sealant for concrete joints. Sealant products that meet this standard and have a displacement capacity of not less than 12.5E are suitable for the installation of doors and windows.
1.3 JC/T 485-2007 building window elastic sealant
JC/T 485-2007 refers to JIS A 5758:2004 "building materials" and JIS A 1439:2004 "test method of building sealing materials". Sealant is divided into Grade 1, Grade 2 and grade 3 according to the requirements of physical and mechanical properties (entry "mechanical properties" provided by industry Encyclopedia), and the main mechanical performance index requirements of each level are shown in Table 2. This standard refers to the Japanese standard, so it is quite different from the above two standard grades, but its classification is mainly based on the displacement capacity of sealant.
This standard specifies the product classification, requirements, test methods, inspection rules, etc. of elastic sealant for building doors and windows and glass inlay, applicable Product types include silicone and elastic sealant with list of synthetic polymers materials (entry "polymer materials" provided by industry Encyclopedia) as the main component except silicone. This standard is only applicable to joint sealing of doors and windows and glass inlay, not to building curtain walls and hollow glass.
2. Correct selection of sealant
2.1 correctly select products that meet the standards
in the process of sealant selection, attention should be paid not only to the standards it meets, but also to the corresponding displacement level. Displacement capacity is the most critical index to measure the elasticity of sealant. The higher the displacement capacity, the better the elasticity of sealant. The processing and installation of doors and windows should choose products with displacement capacity not less than 12.5 to ensure the long-term air tightness and water tightness of doors and windows.
GB/T 14683 has two displacement capacity levels of level 25 and level 20, and the product quality conforming to this standard is relatively high.
During the installation and use of doors and windows, the bonding effect between ordinary sealant and cement concrete is usually worse than that with aluminum for door and window or glass. Therefore, the sealant used for door and window installation is more suitable for products conforming to JC/T 881.
JC/T 485 because the reference is the Japanese standard, the standard classification and performance index are very different from other joint sealant. In order to unify the standard system, this standard will be changed to a classification method similar to other joint sealant standards. Therefore, there are fewer and fewer products adopting this standard in China. Moreover, the displacement capacity of grade 3 products in this standard is low, which is not suitable for the processing and installation of doors and windows with higher requirements.
High-displacement products have stronger ability to withstand joint displacement changes. The author suggests that high-displacement products should be selected as much as possible.
2.2 correct selection of sealant products according to application
hidden window and hidden frame opening fan need structural sealant to play the role of structural bonding. Structural silicone sealant must be used, and its bonding width and thickness should meet the design requirements.
During the installation process of doors and windows, sealant for stone joints or joints with stone on one side should be selected as special sealant for stone conforming to GB/T 23261 standard.
Fire-proof doors and windows or building exterior doors and windows that require fire-resistant integrity are more suitable for fire-proof sealant.
For application places with special requirements for mildew prevention, such as kitchens, sanitary ware and dark and humid parts, it is appropriate to use mildew-proof sealant for joint sealing of doors and windows.
2.3 do not choose oil-filled silicone sealant
compared with other kinds of sealant, silicone sealant is characterized by excellent UV aging resistance and climate aging resistance, thus becoming a building curtain wall, doors and windows and hollow (entry "hollow" provided by industry Encyclopedia) the first choice of sealant for glass. However, not all silicone sealant have excellent aging resistance.
At present, the market is full of a large amount of oil-filled door and window glue, which is called "circulating glue". This kind of product is filled with a large amount of mineral oil and has poor aging resistance, which will lead to many quality problems.
1) composition of oil-filled silicone sealant
silicone sealant is mainly composed of three parts: Silicone basic polymer, filler and auxiliary agent. Among these three raw materials, the price of silicone basic polymer is high, and the content in reasonable silicone sealant formula is also the highest, therefore, its cost often accounts for more than 75% of the total silicone adhesive raw material cost. Considering the performance, the content of silicone basic polymer in silicone sealant products with excellent quality can reach 50% or even higher; However, some manufacturers only consider the cost and ignore the performance. In order to reduce the cost of silicone sealant, add a large amount of low-cost filler to the sealant and add mineral oil, thus greatly reducing the content of silicone base polymer. With mineral oil silicone sealant, it is called "oil-filled silicone sealant" in the industry ". Mineral oil belongs to saturated alkane petroleum distillation. Because its molecular structure is quite different from that of silicone, it has poor compatibility with silicone sealant system. After a period of time, it will migrate from silicone sealant, it permeates and slowly oxidizes when exposed to light and heat (the entry "Oxidation" is provided by industry encyclopedia). Therefore, the elasticity of the oil-filled sealant is OK at the beginning. After using it for a period of time, the filled mineral oil migrates and penetrates from the sealant, and the sealant will harden, crack, even the problem of non-bonding occurs.
Most low-priced silicone sealant on the market is filled with mineral oil, and its silicone base polymer content is much lower than 50%, and some even less than 20%.
2) influence of silicone sealant composition on aging resistance
reasonable formulation of silicone sealant is the basis to ensure its performance. We know that the excellent aging resistance of silicone sealant is determined by its special molecular structure with silicon-oxygen-silicon bond as the main chain, the content of silicone basic polymer directly affects the long-term aging resistance and durability of silicone sealant. If silicone sealant is mixed with mineral oil and cheap filler, the content of silicone base polymer will decrease obviously, and its durability will be seriously affected!
On the surface, these low-cost "oil-filled silicone sealant" are not much different from non-oil-filled silicone sealant. Some products even have good appearance, very bright, fast curing speed, and good initial curing mechanical properties. However, with the extension of service time, the difference between oil-filled silicone sealant and non-oil-filled silicone sealant gradually appears.
Figure 3 is a comparison between oil-filled silicone sealant and non-oil-filled silicone sealant in accordance with the uv aging requirements in american standard ASTM C 1184 for 5000h uv aging test, filled with 15% mineral oil silicone sealant, before the 5000-hour aging test, there was almost no difference between the maximum strength elongation and the non-oil-filled silicone sealant. However, after 500 hours of aging, there is a significant difference in its performance. The elasticity of oil-filled silicone sealant drops sharply, the colloid hardens and loses elasticity. After 3500 hours of aging, the adhesion also has problems, serious degumming (the entry "Degumming" is provided by industry Encyclopedia) has occurred. However, the performance of silicone sealant without oil remained unchanged after 5000 hours of aging test.
3) harm of oil-filled silicone sealant
door and window sealant is mainly used for joint sealing of doors and windows to ensure the air tightness and water tightness of doors and windows. When oil-filled silicone sealant is applied to door and window sealing, the sealing failure often occurs in less than one to two years, resulting in water leakage and energy consumption increase of doors and windows, which seriously affects the normal use.
If the oil-filled door and window sealant is in contact with the hollow glass, the filled mineral oil will migrate and penetrate into the hollow glass, resulting in a sealing butyl rubber of the hollow glass being dissolved and oil flow phenomenon.
4) cost analysis of oil-filled silicone sealant
figure 4 is the cost comparison analysis of high-quality sealant and inferior sealant after long-term use. Choosing high-quality sealant products, although the price of purchasing sealant is slightly higher in the initial stage, it can preserve its service performance for a long time without quality problems. Choose low-priced inferior "oil-filled sealant". Although the price is cheap, the initial input cost is slightly lower; However, after the problem occurs, the later maintenance cost, the product cost, labor cost, brand loss and so on, these costs may be several times or even dozens of times the price of sealant itself; Not only does it not save costs, but it adds a lot of trouble to users.
Sealant occupies a low cost in doors and windows, but it is crucial to quality and service life. Doors and windows are an organic combination of performance systems, which requires higher requirements on the quality and performance stability of each component material. Therefore, the quality and performance stability of sealant are very important. "Oil-filled silicone sealant" not only brings quality problems and potential safety hazards to users, but also causes serious damage to the brand reputation of doors and windows and the reputation of owners. These losses cannot be calculated at cost.
5) identification of oil-filled sealant
the national standard GB/T 31851-2015 "detection method of structural silicone sealant medium alkane plasticizer (entry" plasticizer "provided by industry encyclopedia)" was released in july, 2015 and implemented on june 1, 2016. This standard is applicable to thermogravimetry analysis, thermogravimetry and infrared spectrum analysis methods, quantitative or qualitative detection of alkane plasticizer in structural silicone sealant (entry "plasticizer" provided by industry Encyclopedia) agent (mineral oil), it is also applicable to other silicone sealant.
The thermogravimetry test method specified in this standard can quantitatively determine the content of alkane plasticizer in the tested sample, but this method is only applicable to two-component sealant. The analysis method of infrared spectrum test adopts fourier transform infrared spectrometer (fourier transform infrared), which can be applied to one-component and two-component sealant at the same time, but can only be qualitative. Both of the above two methods can quickly identify whether the sealant is filled with oil, but professional instruments and professional analysts are needed. In addition, GB/T 31851-2015 "detection method of alkane plasticizer in structural silicone sealant" also contains the thermogravimetry method, which takes advantage of the characteristics of alkane plasticizer highly volatile at high temperature, adopts blast drying box and analytical balance, general laboratories can have conditions for testing.
Although the three methods stipulated in GB/T 31851-2015 can identify whether silicone sealant is "oil filled", they must have the basic conditions of the laboratory. How to effectively identify on the construction site or production workshop without laboratory conditions? Here, the author introduces a simple and very effective identification method-plastic film testing method. This method uses the principle that the compatibility between mineral oil and silicone adhesive system is poor, and it is easy to migrate and permeate from silicone adhesive system. Fully contact the oil-filled silicone sealant with plastic (entry "plastic" provided by industry Encyclopedia) film (entry "film" provided by industry Encyclopedia), and mineral oil will penetrate into the plastic film, the plastic film becomes uneven. This method is applicable to both single-component and two-component sealant. The experiment also found that the larger the amount of mineral oil filled, the shorter the shrinkage time of plastic film and the more obvious the shrinkage phenomenon.
The material required for this method is only a flat soft plastic film (such as agriplastic film and PE film). During the test, apply the sealant sample on the plastic film and scrape it flat to make it have a larger contact area with the plastic film, as shown in figure 5. After several hours, generally within 24 hours, the sealant can be identified if it is filled with oil. If the sealant is filled with oil, the plastic film in contact with it will shrink and wrinkle (see figure 6), while the plastic film in contact with it will not shrink and wrinkle even if the sealant is not filled with oil for a longer time.
2.4 selection of product brands
sealant has developed rapidly in the past ten years. At present, there are many manufacturers in the market, with fierce competition and mixed products. According to the feedback from the industry, some doors and windows products have the phenomenon of joint sealing failure caused by sealant quality problems within the design service life, even less than one year. The manifestations include bonding failure, glue-line shrinkage, glue-line cracking, pulverization, oil leakage, dissolution of hollow glass butyl rubber lead to hollow glass failure and other phenomena, causing heavy losses to users and causing serious negative effects to the sealant industry. Therefore, the author suggests that users should consider the product brand when choosing sealant, and how to choose the product brand, and suggest users to consider from the following aspects:
1) Product Quality stability
as we all know, a batch of qualified products does not mean that each batch of products is qualified, and the stability of product quality is sometimes more important than its outstanding performance. Some manufacturers' product inspection reports claim to meet a certain level of a certain standard. In actual production, due to the quality fluctuation in the production process and the quality control level, this causes the product performance to decline and fails to reach its claimed level. The importance of quality stability is self-evident, while ensuring quality stability depends on technical strength, advanced automation equipment and management system, and depends on years of accumulation. It is suggested to choose enterprises that have passed the certification of ISO 9001/ISO 14001/OHSAS 18001 quality, environment, occupational health and safety integrated management system and enterprises with automatic continuous production lines. It is hard to imagine that a manufacturer without production experience, technical team, advanced production equipment and perfect quality management system can produce products with stable quality without fluctuation.
2) After-sales service ability and level
due to the use of materials, equipment, environmental impact and the proficiency of personnel operation, sometimes sealant products will encounter some problems during use. If the service of sealant manufacturers is timely and effective, usually, the problem will be solved quickly. If the service capability of the manufacturer cannot keep up with it and the service is not timely, it will have a great impact on the construction period and construction quality.
3) product price
for users, the lower the product price is, the better. Users need appropriate and cost-effective products. Only by considering the price and the above factors can they choose products with high cost performance. Sealant accounts for a very low proportion in the cost of the whole door and window, but it has a great influence on the quality and service life of the door and window. Although inferior products are cheap, their bonding and sealing performance and durability decrease obviously, which will bring many quality problems and cause great losses to the brand reputation of door and window users, often far exceeds the product price of sealant.
Summary of the editor: When you choose sealant, do not choose oil-filled silicone sealant. When selecting, it is necessary to consider the correct selection of practical use and select sealant products that meet the corresponding standards. Under this premise, it is also necessary to put forward higher requirements on the quality and performance stability of sealant, select products with high displacement level and high quality as much as possible, and pay attention to product brands, quality stability and after-sales service quality.
