ã€China Aluminum Industry Network】1Insulation Material Introduction Nylon 66 (PA66) insulation strip of the matrix resin is nylon 66, namely polyamide 66, which is one of the important varieties of engineering plastics, with high mechanical strength and excellent The 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 is derived from the backbone chemical bonds and intermolecular interaction forces. The characteristic functional groups in the molecular structure of Nylon 66 resin—carbonamide 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 after heat-absorbing and their effects on the wearing strips 2.1 Corresponding relationship between the time and intensity of the heat-insulating strips and the amount of water absorbed Due to the water-absorbing characteristics of nylon 66's own materials, the nylon 66 heat-insulating strips suffer from reduced mechanical properties after they absorb water. The phenomenon shown below in Figure 1 is a graph of the strength of the heat-insulated bars and the amount of water absorbed as a function of standing time.
From the above figure 1, we can see that I-14.8 insulation strips have reduced their strength by 44% when placed in a standard temperature and humidity (23±2)°C, (50±5)% environment for about 900 days, and the larger water absorption capacity is 4.14%. , GB/T23615.1-2009 national standards in the provisions of type I insulation bar after drying strength ≥70MPa, water immersion after 1000h normal temperature intensity ≥35MPa, due to the water absorption characteristics of the insulation bar, in the long-term use will continue to Absorption of water in the air will decrease in strength until the saturation of the water is stable. In addition, ultraviolet and thermal aging will reduce the mechanical properties of the insulation strip. Therefore, the ultimate performance of the insulation strip is actually saturated water absorption and aging. The ultimate 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 relationship between the placement time and dimensional change of insulation bars The effect of water absorption on the dimensions of nylon 66 insulation bars is still significant, although the dimensions of the insulation bars are different for open-toothed and rolled insulation profiles. The impact is not great (just need to adjust the wear strips. Rolling process parameters), but for some curtain wall profiles that do not require opening and rolling, the effect of dimensional changes of the insulation bars will be greater. 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)
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 strips on the stripping process The thermal insulation strips will have a significant impact on the reversal of the profile after the water is saturated. As the stripping temperature reaches about 200°C, the moisture inside the strip will be hard to evaporate instantaneously. When the thermal insulation strips return to the spray after saturated absorption of water, bubbles will appear, resulting in 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 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 Notes on Use of Insulating Bars 3.1 Aluminium Profiles Manufacturers to establish a reasonable inventory of water absorption is an inherent characteristic of nylon 66 insulation, so aluminum manufacturers should wear bars as soon as possible after storage, excessive moisture content will affect the efficiency of wearing or Aluminium profiles cause foaming during re-injection. It is recommended that the insulation strips be stored at a temperature of 20°C to 30°C and a humidity of ≤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 within 3 days before wearing. The product can absorb certain moisture, reduce brittleness, and improve toughness.
3.2 Selection of Reasonable and Effective Testing Items As there are more than a dozen testing items for national standards and benchmarks, and some projects require 1000 hours or more professional testing equipment to test, it is not necessary for the profile manufacturers to increase costs significantly. It is necessary to selectively test important items. 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 Heat insulation strip belongs to polymer composite materials, aluminum profiles belong to inorganic metal materials, the two through mechanical rolling bite complex, if you do not pay attention in the composite process may cause problems, so insulation strip manufacturers and profile manufacturers, Door and window factories should understand each other and communicate with each other, solve the technical problems that arise in time, and join hands in doing our common energy conservation.
Due to the great differences in the coefficient of linear expansion between the heat insulation strip of PVC material and the aluminum alloy, as well as its insufficient strength and poor anti-aging properties, the safety of use cannot be guaranteed. It has already been eliminated by the European door and window curtain wall industry, and has also been banned by China. However, due to the poor standardization of China's construction industry and the low cost of PVC insulation, many unscrupulous manufacturers have penetrated the door and window curtain wall market by various means. This has now become a major safety hazard for China's door and window curtain wall industry. Deterioration of doors and windows caused by inferior heat insulation strips has been heard. It is expected that there will be an increase in the number of doors and windows caused by inferior heat insulation strips in the next decade.
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