1. The meaning of stabilization The stabilization of nylon 66 insulation strips involves two aspects: 1 is the thermal stabilization of nylon 66 insulation strips; 2 is the light stabilization of nylon 66 insulation strips. Thermal stabilization has the effect of determining the stability of nylon 66 insulation strips in the process of quality assurance during the processing of nylon 66 insulation strips, and light stabilization has an immeasurable impact on ensuring the long-term safe use of nylon 66 insulation strips. . With the extensive use of nylon 66 insulation strips in building energy-saving doors and windows, owners and construction parties pay more and more attention to the quality of nylon insulation strips. The Ministry of Construction issued a document stipulating that the industry standard for heat insulation strips (ie JG/T 174-2005) shall be implemented from November 1, 2005, which strictly regulates the quality of heat insulation strips. The stabilization of nylon 66 insulation strips is very important to whether the insulation strip products can meet the requirements of industry standards. Therefore, we hope that the stabilization of nylon 66 insulation strips can attract the attention of the industry and make relevant industry standards deeply rooted in the hearts of the people. The healthy development of energy-saving doors and windows industry.

　　 2. Nylon 66 molecular structure and stabilization Nylon 66 is a polymer material formed by the condensation polymerization of hexamethylene diamine and adipic acid, and its molecular structure is as follows: -(CH2)5-CO-NH-CH2-(CH2)5-. In the molecular structure of nylon 66, the methylene group -CH2- next to the NH group is the weakest link. In the presence of oxygen at high temperature (greater than 120°C), oxygen first attacks the hydrogen atom in the above-mentioned -CH2- Peroxide is formed. Peroxide is easily cracked at high temperature to form free radicals. The free radicals come back and attack the -CH2- next to the NH group, and then the nylon molecular chain breaks. This is the thermal oxidative degradation process of nylon 66. In addition to thermal oxygen degradation, nylon 66 also suffers from hydrolysis at high temperatures. This is because the synthesis reaction of nylon 66 is a chemical equilibrium process, which is reversible, expressed as follows: n(CH2)5CH2NH2 + nHOOC-(CH2)5→-[(CH2)5-CO-NH-CH2-(CH2 )5-]n +nH2O When there is water at high temperature, the above reaction will proceed to the left, that is, hydrolysis, and the result of hydrolysis will also cause the nylon molecular chain to break. When nylon 66 heat insulation strips are processed in a molten state, the degradation process of nylon 66 itself is complicated, which includes both thermal oxygen degradation and hydrolysis. In addition to the thermal oxygen degradation and hydrolysis mentioned above, the danger of chain scission of nylon 66 may also come from photodegradation induced by ultraviolet light. When nylon 66 is exposed to ultraviolet rays in the range of 300nm-400nm, the carbon-nitrogen bond in the nylon molecular chain will be broken, and the methylene -CH2- next to the NH group will also be disproportionated to produce free radicals. The two work together. The result is that the nylon molecular chain is broken, and the molecular weight of nylon decreases. Whether it is thermal oxidative degradation, hydrolysis or photodegradation, the molecular weight of nylon is reduced. The performance of the insulation strip is that the strength of the insulation strip is sharply reduced, while the toughness is lost, and the brittleness of the insulation strip is greatly increased.

3. Nylon 66 thermal stability and quality assurance. Nylon 66 is basically in a high-temperature melt state during the processing and molding process, and is extremely susceptible to thermal oxidative degradation and hydrolysis, which is essential for maintaining the high strength and high toughness properties of the heat insulation strip itself. It is very unfavorable. In order to minimize the heat sensitivity of nylon 66, heat stabilizers and anti-hydrolysis agents must be added. Nylon 66 heat stabilizers are mainly divided into inorganic salts, organic amines and organic phenols. Inorganic salts include copper salts, iodized salts and phosphates, etc., which are characterized by high efficiency and low price. The disadvantage is that they have poor compatibility with nylon and are easily extracted by water. Organic amines and organic phenols are characterized by their excellent compatibility with nylon and are not easily extracted by water. The disadvantage is that they are relatively expensive. After years of research, we have successfully developed a composite heat stabilizer specifically for the extrusion of nylon 66 heat insulation strips. Facts have proved that the effect of this composite heat stabilizer is very significant. It can ensure that nylon 66 heat insulation strips are forming No obvious degradation occurs during the process, and the original high performance of the material is maintained. Interestingly, some nylon 66 heat stabilizers have a good synergistic effect on the light stability of nylon 66. While they play the main function of heat stabilizers, they can also assist the main light stabilizer of nylon 66 to protect the nylon molecular chain. It is not broken due to ultraviolet rays. After years of research, we have screened out this type of dual-function heat stabilizer, and found that the effect is very good in actual use.　　

4. Light stability of nylon 66 and long-term use of insulation strips The thermal stability of nylon 66 mainly involves quality assurance during the processing and molding of insulation strips. The ambient temperature of the insulation strips generally does not exceed 50 during actual use. ℃, such a temperature will not cause any obvious damage to nylon 66 insulation strips. However, as a part of the overall window frame, the thermal insulation strip is inevitably exposed to the ultraviolet rays of the outdoor sunlight, so the light stability of nylon 66 is closely related to the long-term use of the thermal insulation strip. There are many kinds of light stabilizers used for nylon on the market. According to their chemical structure, they are roughly divided into benzophenones, benzotriazoles and hydroxybenzotriazines. It should be noted that each light stabilizer has its suitable host polymer and ultraviolet light wavelength range. After many repeated experiments, we finally determined the structure type of light stabilizer that is very effective for nylon 66. Combining this light stabilizer with some of the heat stabilizers discussed above has the following advantages: (1) Certain nylons The heat stabilizer of 66 has a dual function, and they have a good synergistic effect on the light stabilization of nylon 66; (2) The use of a compound light stabilizer combination can reduce the amount of expensive main light stabilizer, so as to achieve a good Cost-effective. According to the industry standard of the Ministry of Construction JG/T 174-2005 "Hard Plastic Heat Insulation Strips for Construction", the most important strength index of the heat insulation strips after UV aging for 200 hours-the transverse tensile strength should be maintained at 60N/ mm or more, in other words, if calculated according to the intensity of 120N/mm before UV aging, the remaining strength of the heat insulation strip after UV aging should be above 50% of the initial value. Our experimental data shows that if no light stabilizer is added, the transverse tensile strength of the heat insulation strip after ultraviolet aging will drop significantly to below 50N/mm; using a single light stabilizer system, the transverse tensile strength after ultraviolet aging can reach 70N/mm, and the use of a compound light stabilization system can once again increase the strength of the heat insulation strip after UV aging, at least it can be maintained above 80N/mm, the effect is very obvious.

　　5. It is recommended that the stabilization of nylon 66 heat insulation strips involves the final quality of the product and the safety of long-term use, and should arouse high attention from users. It is recommended that users not forget to ask the provider for relevant test reports and long-term quality assurance commitments when using and screening heat insulation strips, and do a good job of quality tracking during use. In particular, the light stability of the heat insulation strip is directly related to the long-term use of the heat insulation strip. At present, the actual use time of the heat insulation strip and the heat insulation aluminum alloy profile in my country has not exceeded ten years, so do a good job of heat insulation. The use of quality tracking work and the accumulation of relevant data will undoubtedly have a very good guiding significance for the development of the entire industry.