As a key component of the heat-insulating aluminum alloy material, the heat-insulating strip has also created a brand-new product field with the application of insulated aluminum alloy doors and windows and curtain walls. In short, the heat-insulating aluminum alloy divides the original one-piece profile into two on the basis of the conventional aluminum alloy, and then connects the two separate parts together by mechanically combining the two heat-insulating strips.
The nature of the use of the insulation strip determines that it must have high strength and low conductivity at the same time, otherwise it will cause significant quality hazard to the insulated aluminum alloy doors and windows and curtain wall (insufficient strength will cause the insulated aluminum alloy from the insulation strip The joint breaks), or loses the meaning of heat insulation (high conductivity can not guarantee the insulation effect), so the material selection and manufacturing process of the insulation strip is very important.
First, how to distinguish
Under natural scattered light, visual inspection was performed at a distance of 0.5 m with normal vision (without using a magnifying glass). The appearance of the insulation strip should be smooth, flat and uniform in color, and the surface should not have any appearance defects that affect the use. Straight bars are not allowed to break, and the number of broken ends of the coil is not more than two.
2, break the experiment
Arbitrary sampling for manual cutting experiments, nylon insulation strips can feel good toughness and strength when bent, bending to the ends will not break, even if the fracture is slow cracking; some nylon insulation strips are not brittle Obviously, when there is a certain distance from the two ends, a multi-segment splitting phenomenon occurs, or the toughness is obvious, and the bending is repeated repeatedly; the PVC heat insulation strip is very soft, basically has no strength, and is repeatedly bent without breaking.
3, the dimensional accuracy.
Using the vernier caliper (more accurate micrometer) to measure the dimensional accuracy of the thermal insulation strip, it can be found that the nylon thermal insulation strips have different dimensional deviations of less than 0.1 mm in different batches or different thermal insulation strips, and the parallelism standard; The deviation of the dimensions of different batches of different nylon insulation strips or PVC insulation strips or different parts of the same insulation strip is at least 0.1 mm.
Second, the impact of unqualified insulation strips on production
1. Changes in the heat-absorbing strip after water absorption and the effect on the strip
The saturated heat-absorbing strip will have a significant effect on the back-spraying of the profile. Since the profile back-spray temperature reaches about 200 °C, the moisture inside the heat-insulating strip is not easily volatilized at the moment, so when the heat-insulating strip is saturated and absorbs water, it will return to the spray. Air bubbles caused the profile to fail. Therefore, the amount of water absorption of the heat insulating strip is strictly controlled for the back-spraying process.
Water absorption is an inherent characteristic of nylon 66 insulation strips. Therefore, it should be worn as soon as possible after storage, and the required amount of FIFO should be used. Excessive moisture content will affect the wear efficiency or the aluminum alloy material will be sprayed back. To cause foaming, it is recommended that the insulation strips have an optimum temperature of 20 ° C to 30 ° C and a humidity of ≤ 55%. Because nylon 66 is brittle when the weather is cold and dry, it is recommended to properly open the product packaging 3 days before wearing the strip. The product can absorb certain moisture, reduce brittleness and improve toughness.
2, the relationship between the placement time and size of the insulation strip
The water absorption rate has a significant effect on the size of the nylon 66 insulation strip product. Although the size change of the insulation strip is not significant for the open-toothed and rolled insulation profiles (only need to adjust the wear and roll, roll Pressure process parameters).
3, insulation strip twist
In the production, there is often a twisting phenomenon of the wire rod, mainly because the heat insulation strip is too tight when it is finished, and the heat insulation strip is piled up during the transportation, which causes the rubber strip to be twisted, which has an impact on the efficiency of the actual production. At the same time, it also brings trouble to production.
4, the impact of horizontal tensile strength
When used in winter and summer, there is a large temperature difference between the heat-insulating profiles of the insulated aluminum window and the outer two-cavity profiles. This temperature difference will cause different deformation trends between the inner and outer cavities. In summer, the temperature of the outer cavity profile is high, causing the outer arch to retract. In winter, the temperature of the outer cavity profile is low, causing the inner arch to contract. This non-stop arching stress causes the heat insulating profile to produce a large lateral tensile force in the middle. If the transverse tensile strength of the insulation strip is low, breakage will occur, resulting in quality problems in the insulation profile.
Third, the danger of fake nylon insulation strip
If the mechanical strength of the insulation strip is not sufficient, it can not guarantee a good wind pressure resistance performance, which directly affects the safety of the building; if the heat resistance is not good, it directly affects some surface treatment processes in the production process of the heat insulation aluminum alloy material; Chemical resistance not only affects the chemical treatment process in the process, but also hinders the cleaning work in the future use; if the coefficient of linear expansion is large, the creep resistance is poor or the dimensional stability is not high, the heat insulation strip will be caused. The deformation between the aluminum alloy profile is loosened, and the airtightness, sound insulation effect and heat preservation of the energy-saving door and window are reduced.
Fourth, high quality insulation strip
1. The surface of the high-quality heat insulation strip is black and matte, and the whole is smooth and flat, without shrinkage holes, no looseness, no scratches and mold extrusion marks. The minerals are particularly lustrous and visible. There is no parting line mark on the end face of the hot strip.
2, the longitudinal tensile strength reflects the mechanical properties of the thermal insulation strip in the longitudinal direction, and the elastic modulus is one of the indicators that can best characterize the performance of the material. In engineering, the elastic modulus is called the stiffness of the material, which is characterized The resistance of the material to elastic deformation, the greater the value, the smaller the elastic deformation produced under the same stress, and the more rigid the material.
3. When the product is subjected to dynamic load, the impact strength (toughness) performance index of the material is required. The impact strength also indicates the toughness performance of the material. It is one of the performance indicators of the material selection. Good toughness can ensure that the heat insulation strip is assembled. Has a relatively high yield.