At present, there are many people who mistakenly believe that the production of aluminum alloy doors and windows as long as the cutting equipment cutting precision is high, with a proper corner code, combined with a fixed angle of the unit angle, it can make the aluminum alloy door and window corner strength and sealing performance Claim. In fact, most of the aluminum alloy doors and windows using corner connections are produced using this process. This simple mechanically fixed connection is a rigid connection that is difficult to adapt to the various forces encountered by the doors and windows during production, transportation, installation and long-term use without being damaged.
First of all, we need to understand the physical properties of aluminum alloy profiles.
Aluminum alloy profiles have the same temperature differential stress as any other material. Thermal stress refers to the stress caused by a change in temperature of a material, usually a linear expansion/contraction coefficient.
We can calculate the dimensional change of the aluminum alloy profile in the normal use temperature range, that is, the linear expansion/contraction rate formula is as follows:
L=L0(1+αΔT)
Where: L: the length after the change
L0: original length
α: expansion/contraction coefficient, for aluminum alloy profiles, in the range of -40°C+50°C, the value is 2.4×10-5/°C
ΔT: change in temperature (Celsius)
Calculation example: The original length of the aluminum alloy profile is 1 meter, and the temperature variation is +50°C-40°C=90°C.
L=1m (1+2.4×10-5°C×90°C)=1.00216m
That is to say: 1 meter long aluminum alloy profiles will produce a 2.16mm length change at a temperature change of 90°C. For aluminum alloy doors and windows with only rigidly connected corner strengths, this amount of change will have a destructive effect, causing the misalignment or deformation of the positions of the parts at the corners of the doors and windows, which is reflected in the corners of the doors and windows is undoubtedly a fatal flaw. . This kind of defect is that there is no way to make up for any rigid connection between a bolt or a cornering machine.
Secondly, during the production and installation of aluminum alloy doors and windows, due to movement errors during handling, transportation, and installation, and after installation of doors and windows, aluminum alloy doors and windows have to withstand their own weight for a long time, and withstand the deformation of window openings and building walls. Stress errors, switching spikes, wind pressure, environmental sound waves, and other peak shocks and vibrations of different frequencies, which sometimes induce resonance in doors and windows, affect the overall strength of doors and windows.
All of these reasons will cause the gaps in the corners of windows and doors to gradually increase and dislocate over time, resulting in airtightness, watertightness, sound insulation, and dust-reducing performance of doors and windows. In severe cases, doors and windows will also be deformed and have undesirable consequences. At present, more and more engineering disputes have arisen, which has seriously affected the overall reputation and image of aluminum alloy high-quality doors and windows.
In fact, the aluminum alloy doors and windows of the corner strength and sealing as long as the use of special aluminum alloy doors and windows can be corner glue, but unfortunately most of the windows and doors and the developers, administrative departments and related building design, supervision and other units do not really understand The special role of glue to improve the overall quality of doors and windows. Some door and window assembly plants did not use adhesives or mistakenly used glass adhesives, structural adhesives, and epoxy adhesives as aluminum alloy door and window adhesives.
At present, there are three types of plastics that are often posing as corner glues on the market:
1, glass glue
Also known as silicone sealant; poor adhesion to aluminum alloys, poor weatherability, easy aging, low hardness, too much elasticity, the gel does not expand when curing, can not make the corners and the cavity closely bonded into one.
2, structural adhesive
The adhesiveness to the aluminum alloy is poor, the curing time is long, the product has many odors, does not swell when cured, and does not produce high strength.
3, epoxy adhesive
After curing, there is no elasticity and it can not adapt to the form of micro-shock, easy to crisp and broken, the long-term strength after the angle is not enough, will produce cracking, dregs phenomenon.
Why do we advocate the need to use a special group of glue? Because special aluminum alloy door and window group rubber has the following characteristics:
1. The colloid is a modified polyurethane-based adhesive that does not contain solvents and meets environmental protection requirements.
2, the initial curing time is short, about 10 minutes, help to improve production efficiency. Divided into single and two-component type, it is more suitable for the requirements of the two processes of “corner-coded plastic plugging and corner integral injectionâ€.
3, the hardness after curing is very high, but not brittle, with low elasticity and excellent waterproof performance, so that the corner and the profile of the cavity wall adhesion for the tough connection, so as to make up for, reduce the window corner of the various deformation, cracking situation Effectively solve the leakage problem at the corners of doors and windows.
4. After the single-component adhesive corner glue is completely cured, the shear strength of the effective adhesive part of the corner and profile cavity can reach 10.3N/mm2, and the adhesive strength of the two-component adhesive group can reach 18N/mm2. Greatly improve the window angle strength. That is to say, the shear angle strength of ordinary 60 series profiles in China can exceed.
5. The colloid slightly foams and expands during the curing process to form an elastic pad between the metal and the metal, which effectively weakens the transmission of various forces and functions as a shock absorber and a cushion.
6, strong weather resistance, ability to -40 °C +80 °C temperature changes, colloidal white or translucent, the colloid will not turn yellow in the short term. The two-component adhesive can withstand 30 minutes at a high temperature of 230°C and is suitable for post-processing applications such as powder coating.
7, with the special cleaning agent, a small amount of plastic spill is easy to clean, will not damage the surface of the coating and paint surface, non-toxic environmental protection.
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