[China Aluminum Industry Network] 1 Insulation Material Introduction
Nylon 66 (PA66) thermal insulation strip base resin is nylon 66, namely polyamide 66, which is one of the important varieties of engineering plastics, with high mechanical strength and excellent wear resistance, aging resistance, self-lubricating And heat resistance. Its excellent low-temperature performance, self-extinguishing, acid and alkali and most of the inorganic salt solution, oil and organic solvents. After being reinforced with glass fiber, its mechanical properties, heat resistance, dimensional stability and chemical resistance will be greatly improved. As a heat insulation strip applied to energy-saving windows and doors, it can resist wind pressure and salt fog very well. Corrosion, etc., more importantly, the linear expansion coefficient of the glass fiber reinforced nylon 66 insulation strip is very close to the aluminum alloy, and the overall performance after compounding with the profile is good. Practice has proved that this is the ideal insulation profile that has been successfully developed so far, and it has been used in Europe for many years now.
The strength of nylon 66 derives from the backbone chemical bonds and intermolecular interaction forces. The characteristic functional groups in the molecular structure of nylon 66 resin, the carbamide groups, are always aligned so that each functional group can be in the absence of molecular deformation. Hydrogen bonds are formed, and carbonamide-NHCO- is polar, so water absorption is a characteristic of nylon 66. The absorbed moisture can weaken the interaction between the molecular chains, have a plasticizing effect on the material, lower the glass transition temperature, and increase the product size. Such phenomena. However, water absorption is a two-way process, and some control measures are used to interfere with the effect of water absorption on the product, so as not to affect the use of our insulation products.
2 Changes in heat-absorbing strips and their effect on wearing
2.1 Correspondence between time and intensity of insulation strip and water absorption
Due to the water absorption characteristics of nylon 66's own material, the phenomenon that the mechanical properties of the nylon 66 heat insulation strip is reduced after absorbing water is shown. The following figure 1 is a graph showing the change of the strength and the amount of water absorption of the heat insulating strip with the placement time.
I-14.8 Insulation strips have a 44% decrease in strength at a standard temperature and humidity (23±2)°C, (50±5)% environment for about 900 days, and a large amount of water absorption 4.14%, in GB/T 23615.1-2009 The national standard stipulates that the strength of type I insulation bars after drying should be ≥70 MPa, and the strength should be ≥35 MPa after immersed in water at room temperature for 1000 hours. Due to the water absorption characteristics of heat insulation strips, the strength of water absorption from air will be reduced during the long-term use. Until the saturation of the water can be stabilized, and UV, thermal aging and other factors will reduce the mechanical properties of the insulation strip, so the test of the insulation performance of the insulation strip is actually saturated water absorption and aging of the final performance. Therefore, at this stage, the inspection of heat-resistance performance of thermal insulation strips is a very important test item and should be brought to the attention of various profile manufacturers and related departments.
2.2 The relation between the placement time and dimensional change of thermal insulation strip
The effect of water absorption on the dimensions of the nylon 66 insulation is still quite significant, although for the open-toothed, rolled insulation profiles, the dimensional changes of the insulation bars have little effect (adjustment of the wear bars is only necessary. Pressure process parameters), but for some curtain wall profiles that do not require opening and rolling, the dimensional change of the insulation bar will have a greater impact. Take I-14.8 insulation strip after drying. Its width is 14.802mm, thickness is 1.781mm, height is 4.161mm, and length is 1000mm. It can be changed under the standard environment of the laboratory for different time to get its size change (Table 1 below)
Placement time/day
Width mm
Thickness mm
Height mm
Length mm
90
14.839
1.792
4.176
1002
180
14.871
1.808
4.189
1004
270
14.902
1.823
4.201
1005
360
14.930
1.836
4.210
1006
450
14.955
1.847
4.218
1007
540
14.981
1.852
4.224
1007
630
14.987
1.859
4.227
1008
720
14.991
1.865
4.229
1009
810
15.001
1.868
4.231
1009
900
15.002
1.868
4.231
1009
From Table 1 above, it can be seen that when the I-14.8 insulation strip is placed in the standard temperature and humidity environment for about 900 days, it reaches the saturation of water absorption, while the dimension width increases by 1.35%, the thickness increases by 4.88%, the end height increases by 1.68%, and the length increases. 0.9%.
2.3 The effect of heat insulation on the stripping process
Insulation bars saturated after water absorption will have a more obvious impact on the profile, due to the temperature of the profile back to spray about 200 °C, the insulation of the moisture inside the instant is difficult to volatilize, so when the heat insulation bar saturated water back to spray will Bubbles cause unqualified profiles. At present, the European composite method of heat-insulating aluminum alloy composites is the first to apply the surface after spraying, and in China is to do the first spray and then do the profile composite, resulting in the insulation area, the insulation surface of both sides of the aluminum profile radiation rate from 0.2 is increased to 0.9. The heat radiation of the aluminum profiles on both sides of the heat insulation strip is enhanced, which reduces the heat insulation performance of the profiles. Therefore, in order to improve the heat insulation performance of the heat insulation aluminum alloy doors and windows, the composite processing method of the heat insulation profiles will be changed. After the spraying, the composite processing method was changed to the first composite post-spray processing method, which became the leading processing method for China's future heat insulation aluminum alloy profiles. Therefore, the amount of water absorbed by the insulation bar is strictly controlled for the re-injection process.
3 Insulation Bar Usage Notes
3.1 Profile manufacturers to establish a reasonable inventory
Absorption is the inherent characteristic of nylon 66 insulation strip, so strip manufacturers should wear strips as soon as possible after storage. Excessive moisture content will affect the efficiency of stripping or the phenomenon of blistering when the profile is returned to the spray. It is recommended to save the insulation strip. The preferred temperature is 20 °C ~ 30 °C, humidity ≤ 55%. Due to the brittleness of nylon 66 in cold weather and dry conditions, it is recommended that the outer packaging of the product be properly opened 3 days before wearing. The product can absorb certain moisture, reduce brittleness, and improve toughness.
3.2 Choose a reasonable and effective test item
Since there are more than a dozen test items for national standards and benchmarks, and some projects require 1000 hours or more professional testing equipment to test, the profile manufacturers can selectively test important items without significantly increasing costs. necessary. The following briefly describes some of the test items that individuals consider to be important.
1 Product dimensional accuracy of thermal insulation strips - This project can reflect the stability of the heat insulation strip extrusion process and materials to a certain extent. The high dimensional accuracy can improve the efficiency of stripping and increase the yield of the profile.
2 Absorption rate and horizontal tensile strength of insulation bars - to some extent, it can reflect the pros and cons of composite materials used in insulation strips. If the composites used in the production of insulation strips are specially formulated and modified, then Reducing the water absorption of the heat-insulating strips, the mechanical properties after water absorption remain relatively high. (The water resistance test can be boiled for 4 h instead of water for 1000 h).
3 The tensile strength of the heat-insulating strip after drying can reflect the stability of the heat-insulating strip material and the production process as a whole.
4 Insulation strip tensile strength at high temperature - can reflect the thermal stability of the material of the insulation strip and the stability of the harsh environment, and can indirectly reflect the quality of raw materials. Poor quality raw materials due to more impurities (such as PE, PP, PVC, ABS and other poor heat resistance, low strength polymer materials), its high temperature performance is poor.
4 Conclusion
The heat insulation strip belongs to the polymer composite material, and the aluminum profile belongs to the inorganic metal material. The two are mechanically rolled and bite and compounded. If the composite process does not pay much attention, it may cause problems. Therefore, the heat insulation strip manufacturer and the profile manufacturer, the door and window factory They should understand each other and communicate with each other, solve the emerging technical problems in a timely manner, and join hands in doing our common energy conservation.
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