What is oxidation?
The structural characteristics and physical state of the polymer material itself, as well as the external factors such as heat, light, thermal oxygen, ozone, water, acid, alkali, bacteria and enzymes received during use, cause performance degradation or loss during the application process. For example, yellowing, decrease in relative molecular weight, surface cracking of products, loss of gloss, and more serious, lead to a significant decrease in mechanical properties such as impact strength, tensile strength and elongation, and even loss of use value. This phenomenon is called aging for short.
Aging may occur at all stages of the synthesis, storage, processing and final application of polymer materials. It can lead to the end of the service life of the material and a large amount of waste, resulting in a great waste of resources and serious environmental pollution.
Classification of polymer materials aging problem
In general, the aging of polymer materials can be classified into the following four types of changes:
(1) Changes in appearance. Such as stains, spots, silver streaks, cracks, etc.
(2) Changes in physical properties. Such as quality, size, heat resistance, cold resistance and other performance indicators change.
(3) Changes in mechanical properties. Such as changes in tensile, flexural, and compressive properties.
(4) Changes in electrical properties. Such as insulation resistance, dielectric loss, breakdown voltage, etc.
Polymer materials and their products play a very important role in practical applications. Once aging and failure occurs during use, it will inevitably cause economic losses, and even worse, may cause environmental damage, personal injury, and so on.
Therefore, it is necessary to replace the polymer material products before they become aging. In keeping with the principles of energy saving, low carbon and ecological development, as well as maximizing the functions of polymer materials, the reliability and durability of materials have attracted more and more attention.
Aging of nylon
PA6 and PA66 have the advantages of light weight, high toughness, good electrical insulation and thermal insulation performance, etc. They are widely used in the electronics industry, such as electrical machinery or power tool housings, electrical tuning parts, machine housings, automobile engine blades, etc.
However, as the basic raw material of electronic devices, it is required not only to maintain good mechanical strength within a certain period of use, but also to not change the appearance and color of the product too much after aging, especially some light-colored nylon products with strict appearance requirements, otherwise the performance of electronic products will be reduced and the normal use of the device will be affected.
As the PA6 and PA66 materials for electronic appliances used indoors, they will face higher local temperatures in actual use. Therefore, the long-term heat effect is one of the important factors that make PA6 and PA66 aging; In the actual use environment and conditions, in most cases, oxygen participates in the aging process of nylon, and the combined action of heat and oxygen will greatly accelerate the aging process.
Therefore, it is very necessary to take anti-aging measures for PA6 and PA66.
Anti-aging method of reinforced nylon
It has been found that the addition of antioxidants and blending modification can improve the heat aging resistance of PA materials and greatly extend the service life of the materials.
Commonly used reinforced nylon has thermal oxygen stabilizers, including copper stabilizers, amine and hindered phenol antioxidants, and hydroperoxide decomposers.
According to some data introduction and a large number of experiments, the anti-aging effects of different antioxidant systems are as follows:
Copper salt antioxidant>1098+626 antioxidant system>1098 antioxidant system>1010+626 antioxidant system.
Carbon black has a good UV absorber, so black reinforced nylon materials are more resistant to aging than other colored reinforced nylons.
It has been found that POE-g-MAH elastomer can resist thermal aging to a certain extent in the toughened PA6 system. The combination of antioxidant 1098 and phosphite antioxidant 626 has a synergistic effect in the PA6 system.
Copper salt antioxidant and antioxidant 1098 and its composite antioxidant are all high-efficiency antioxidants of PA6 resin system. Copper salt antioxidant has a more obvious anti-heat aging effect on toughening PA6 system. The antioxidant 1010 compounding system has limited thermal aging resistance to PA6 resin. Reinforced nylon and copper salt antioxidants and 1098 composite anti-oxidation toughened PA6 materials can meet the thermal oxidative aging requirements of the materials.