[China Glass Net] The glass frame of the hidden frame curtain wall and the metal frame are completely connected by the structural adhesive. The cross-linked and solid elastic bond is like a continuous spring to "hang" the glass into the building facade. The application of this technology is far less mature than traditional mechanical connections. Building codes must take into account the risks of owners and pedestrians, system aging and adhesion degradation, unforeseen and uncontrolled factors in the project, and the danger of curtain wall glass falling. Therefore, the correct selection of the curtain wall structural adhesive is particularly important.
The type of curtain wall structural glue is selected in JGJ102-2003 "Technical Specifications for Glass Curtain Wall Engineering", 3.1.4 clearly stipulates: "Invisible frame and semi-hidden frame glass curtain wall, the bonding of glass and aluminum profiles must use neutral silicon. Ketone structural sealant; when the glass curtain wall and the point support curtain wall are coated glass, it should not be bonded with acid silicone sealant.†Why the structural adhesive must be silicone type, because of the molecular structure of the silicone structural adhesive decided. The molecular structure of silicone structural adhesive is mainly Si-O chemical bond, and its chemical bond energy (108kcal/mol) is greater than that of ultraviolet light. Therefore, silicone structural adhesive has weather resistance, water resistance, ozone resistance, ultraviolet resistance, heat resistance and cold resistance. Excellent performance. In addition, acid gels can corrode certain metal materials, so acid coatings cannot be used on the surface of the coated layers of aluminum and coated glass.
The standard for the implementation of silicone structural adhesive is in JGJ102-2003 "Technical Specifications for Glass Curtain Wall Engineering", 3.6.1 clearly stipulates: "The performance of neutral silicone structural sealant and acid silicone structural sealant for curtain wall should be consistent with The current national standard "silicone structural adhesive for construction" GB16776. "GB-16776 is a mandatory national standard.
The earlier relevant foreign standard was ASTMC1184, which was first promulgated in 1991. At present, China's new construction industry standard JG/T475 "silicone structural sealant for building curtain wall" has been released and will be officially implemented on April 1, 2016. This standard refers to the European standard ETAG002, which clearly requires that the silicone structural sealant for building curtain wall has a service life of not less than 25 years. It is more scientific and stricter than the previous domestic and international standards, and provides safety for the building curtain wall.
Silicone structural adhesives have four important performance standards. Whether it is national standard, American standard, European standard or new construction industry standard, the performance of structural adhesive is not graded. Therefore, on the basis of the above two basic conditions, The selection of structural adhesives is still difficult.
To sum up, the important properties of silicone structural adhesives are mainly reflected in the following four aspects:
1. Adhesion is defined as the bond properties of the sealant on a given substrate. Bonding relies on interface physical adsorption, chemical bond generation, and mechanical biting to achieve connectivity. Good adhesion is the basis for ensuring that the sealant achieves its function. It is clearly stated in the requirements of GB16776-20055. 3 that the silicone structural adhesive and the actual engineering substrate must be tested for adhesion.
2. Compatibility is defined as the property of the contact surface of the sealant with other materials to not cause undesirable physicochemical reactions. Other materials generally refer to backing materials such as foam sticks, double-sided tapes, and rubber strips. Compliance is the basis for ensuring that the sealant retains its properties. It is clearly stated in the requirements of GB16776-20055. 3 that the silicone structural adhesive and the accessories for the structural assembly system must be tested for compatibility.
3. Ageing resistance is defined as the time elapsed from the time the sealant is embedded in the seam until its function fails. In the GB16776-2005 standard, it is directly related to the tensile bonding properties after high and low temperature, water immersion and water-ultraviolet light. In the standard, the judgment of the tensile bond strength of the sealant after the curing time for each aging condition is only specified as a small value, but according to the relevant experience and the European standard determination method, the ratio of the strength after aging to the strength under the standard condition should also be calculated. It is the strength retention rate, which should be as large as possible.
4. The width and thickness of the silicone structural adhesive in the actual construction process are calculated by relevant specifications. In JGJ102-2003 "Technical Specifications for Glass Curtain Wall Engineering", the silicone structural adhesive bond thickness ts is given. The calculation formula has a parameter, which is the δ value, and δ represents the displacement bearing capacity of the silicone structural sealant. The values ​​of the δ values ​​of different manufacturers are different. And two restrictions are also given in the 102 specification, the thickness must be greater than or equal to half the width and less than or equal to the width, and the thickness is between 6 and 12 mm. In the new JGJ102 specification, this formula has also been changed. Regardless of the new and old specification formula, the larger the displacement capacity of the silicone structural sealant, the smaller the thickness calculation result and the more cost-saving; in other words, if the thickness value is fixed, if the structural adhesive manufacturer provides the change The greater the bit capacity, indicating that the design is safer. However, according to experience, the preferred value range of displacement capacity is 8%-12%. At present, most of the structural rubber manufacturers' products are less than 8%, generally between 5% and 8%. Then why can the displacement capacity not exceed 12%? If it is too large, it means that the structural adhesive is subject to a little wind and grass, and it will cause a large displacement, and the curtain wall will also have a great risk.
The five major problems and solutions for practical application Silicone structural adhesives have many problems in the actual application process, mainly in the following five aspects:
1. No adhesion and compatibility tests were carried out before construction.
So far, there have been many quality and safety accidents caused by the failure of the structural adhesive and the substrate to pass the unqualified glass. The compatibility reflects whether the structural adhesive and the phase contact attachment have undergone physical or chemical reaction. If the compatibility is unqualified, it will directly lead to discoloration of the structural adhesive, bond failure and performance degradation. Therefore, it is necessary to carry out the adhesion and compatibility tests before construction.
2. Resist the use of primer when construction.
On the one hand, the construction side will increase the construction cost. In fact, the key point is that the construction party has insufficient understanding of the primer. This primer mainly serves as a bridge. It can improve the adhesion and shorten the bonding time, and can also improve. Water resistance and durability of bonding;
3. The maintenance environment and curing time did not meet the requirements.
According to the standard, two-component complete curing requires 14 days of curing, one-component 21 days, but according to the test results, two-component curing for 3 days, single-component curing for 7 days, can basically achieve the final curing and bonding effect. When the temperature is low, the curing time should be extended appropriately.
4, improper selection of profiles in the 102 specification, 3.1.2 clearly stated: "Aluminum alloy materials should be surface anodized, electrophoretic paint, powder spray or fluorocarbon paint spray treatment." And for aluminum alloy surface treatment layer The thickness is also clearly defined, such as anodizing treatment with an average film thickness of ≥ 15 microns and a local film thickness of ≥ 12 microns. However, in the relevant standards and specifications, there is no clear regulation on the treatment method of the aluminum surface. It has been proved that the anodized profile has better adhesion with silicone rubber, followed by electrophoretic painting and doubling treatment. It is powder spray and fluorocarbon paint spray treatment. In addition, the surface treatment layer of the aluminum profile treated by the powder coating and the fluorocarbon paint is relatively inferior in adhesion and durability. If the design uses spray profiles, it is recommended to first fuse before spraying, then protect the rubberized film and spray it.
5. After the construction, the batch peeling and unit part cutting test were not carried out.
The single component cutting test is the finished product breaking test, which is suitable for the inspection of the adhesiveness of the structural sealant in the assembly field. It is used to find problems in the field application, such as the substrate is not clean, the improper primer is used, and the primer is improperly used. Incorrect seam assembly, unsatisfactory design of cemented joints and other problems affecting adhesion (such as substrate surface treatment, temperature and humidity of curing environment, wide thickness of colloid, ventilation, etc.).
It is suitable for pre-construction testing, which can be used to preliminarily determine the bonding effect between structural adhesive and substrate. Although the surface treatment is the same as the actual state of the project, it is a special person test, which basically eliminates the factors of human error, and the wide thickness and air permeability of the colloid are different from the actual situation, and cannot completely replace the result of the rubber cutting test of the unit.
The complete construction system of the curtain wall structural adhesive is a semi-finished product type, which needs to be used correctly in order to obtain a good adhesive sealing effect. According to the experience of market sealant, the problem of cohesiveness of curtain wall engineering often occurs in the construction stage of sealant. Most of them are caused by improper construction or improper maintenance. Therefore, the construction party needs certain construction capacity and work experience. The structure without these conditions can be constructed. The rubber manufacturer provides technical training and guidance to assist in the establishment of a construction quality assurance system.
A complete silicone structural sealant construction shall include the following contents: 1. Report on the adhesion and compatibility of silicone structural sealant and actual substrate; 2. Factory inspection report of silicone structural sealant, delivery Documents, quality assurance documents; 3, technical training for construction personnel; 4, quality inspection before use of silicone structural sealant; 5, quality inspection of silicone structural sealant in use; 6, use record of silicone structural sealant product; Article maintenance record; 8, with the batch peel test, unit piece cutting test;
Basic conditions for strategic partners:
1. It has passed the certification of building silicone structural adhesive, and has at least 10 years of history of silicone structural sealant production, providing structural rubber 25-year warranty;
2, has a wealth of structural rubber engineering examples, and built a curtain wall project file;
3. Have a complete marketing network and technical service team throughout the country to ensure professional technical training and timely on-site service for customers;
4. It has automatic continuous production process equipment;
5. The building silicone structural adhesive has a production capacity of at least 5,000 tons/year and can continuously provide stable structural rubber products;
6, with more advanced management experience and a sound management system and system, at least through the domestic and international well-known companies ISO9001 / ISO14001/OHAS18001 and other three certification;
7. Have a complete quality control system and advanced testing equipment;
8. Have a good corporate culture, long-term strategic development plan and high-quality talent team and talent reserve.
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