As the structural part of the heat-insulating aluminum alloy curtain wall, the strength and stability of the heat-insulating strip under the stress condition is very important. Therefore, the material of the heat-insulating strip determines the fate of the heat-insulating aluminum alloy curtain wall.Nylon 66 insulation strips are analyzed from two aspects and compared with other insulation strips.
Matrix resin thermal insulation
The base resin of nylon 66 insulation strip is nylon 66,namely polyamide 66, which is one of the important varieties of engineering plastics. It has high mechanical strength and excellent wear resistance, self-lubricating property and heat resistance.Its low-temperature performance is excellent, self-extinguishing, acid and alkali resistance and most inorganic brine solutions, oil resistance and organic solvents. After reinforced by glass fiber, its mechanical properties, heat resistance, dimensional stability and chemical corrosion resistance are significantly improved. As a heat insulation strip, it can be applied to energy-saving doors and windows without looseness of metal due to thermal expansion and cold shrinkage, and can well resist wind pressure and salt spray corrosion. PVC and other general plastics have low strength, poor heat resistance and anti-aging performance, and large linear expansion coefficient, and do not match aluminum alloy profiles, Europe has eliminated it. In China, the usage environment of the insulation strip is much more severe than that of Europe. For example, the climate change in the south and the north is much stronger than that of Europe throughout the year. It is obvious that PVC and other insulation strips can not meet the requirements. Some illegal manufacturers use recycled waste of nylon 66 instead of special extruded material. Due to the degradation of nylon 66 at high temperature and the decrease of molecular weight, the mechanical properties of recycled waste of nylon 66 are obviously reduced, which can not meet the usage requirements of insulation strip. Nylon 66 is necessary as the base resin because the insulation strip may pass the test of electric furnace enamel, chemical treatment and other surface technology in the process of forming insulation aluminum profile by combining with aluminum alloy.
Filling substance of insulation strips
Since the glass fiber reinforced nylon 66 has a rough surface, how to obtain a smooth and flat surface is a difficult problem in plastic processing. In order to obtain a smooth and flat surface product, and to reduce costs, some businesses use ordinary minerals (i.e., commonly referred to as fillers) instead of glass fibers to fill nylon 66 to produce insulation strips. The author has collected the insulation strips from several manufacturers on the market for analysis, and found that some insulation strips are filled with all ordinary fillers, such as talcum powder, and some are partially filled with a part of glass fiber. The content of glass fiber is far from 25%(wt) of publicity. Common minerals mainly refer to talc powder, mica, calcium carbonate,etc. The main purpose of filling plastic with them is to reduce the cost. Glass fiber is the most representative of fiber reinforced plastics. The mechanical strength, heat resistance, organic solvent resistance, hardness and creep resistance of fiber reinforced plastics are much better than those of ordinary filler reinforced plastics. Meanwhile, the linear expansion coefficient of glass fiber reinforced nylon 66 is similar to that of aluminum alloy, and the water absorption of nylon can be reduced.
Now there are some so-called nano-filled nylon 66s on the market, boasting significant performance improvements after nano-filled. In fact, the so-called nano-filling is not a new technology. It is a composite material formed by uniformly dispersing inorganic nano-particles including silicate, calcium carbonate, SiO2, TiO2, etc. in the plastic matrix resin with nano-size (generally 1-100 nm), also called polymer-based nano-composite material. Nylon 66 nanoplastics is a kind of treated natural clay mineral-montmorillonite filler dispersed into the polymer by intercalation composite technology to form nanometer nylon 66. The nano-filling amount is relatively small, generally 2%-5%, with limited performance improvement. The disadvantage of nanofilling is that, as with the usual inorganic fillers, the welding strength of plastic decreases. And the toughness (impact strength) of some nanoplastics such as nanometer nylon also decreases.
Hazards of false nylon insulation strip
Either matrix resin or filling fraud will cause damage to the interests of users. If the mechanical strength of the thermal insulation strip is not enough, it can not ensure good wind pressure resistance, which directly affects the safety of the building; if the heat resistance is not good, it will directly affect some surface treatment process in the production process of the thermal insulation aluminum profile. The chemical corrosion resistance not only affects the chemical treatment in the process but also hinders the cleaning work in the later use process. If the linear expansion coefficient difference is large, the creep resistance performance is poor or the dimensional stability is not high, it will lead to deformation and loosening between the thermal insulation strip and the aluminum alloy profile, reduce the air tightness, sound insulation effect and thermal insulation property of the energy-saving doors and windows.In summary, fiberglass reinforced nylon 66 is the best proven material that can not be replaced by other materials.
Method for distinguishing true and false insulation strips
In view of the good and bad insulation strips in the domestic market, ABS (styrene-acrylonitrile-butadiene terpolymer), PP (polypropylene),PVC and other general plastics can only be used as non-structural materials to replace engineering plastics PA66 to manufacture the so-called "insulation strips ", and a simple method for identifying the true and false insulation strips is provided:
The heat insulation strips made of PVC, ABS, PP,PA6(nylon 6) , PA66 and other materials are respectively placed in an oven, and then heated up.The PVC material is softened and degraded at about 900C.The PP material and ABS materials are softened and degraded at about 1600C. The PA6 material was softened and degraded at about 2100C. The thermal insulation strips of PA66 material have no obvious change when the temperature was below 2400C.