What is aging? How to enhance the aging resistance of nylon?

Mar 13, 2023

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The structural characteristics and physical state of polymer materials and the external factors such as heat, light, thermal oxygen, ozone, water, acid, alkali, bacteria and enzyme that they are exposed to in the process of use make their performance decline or loss in the process of application, such as yellowing, reduction of relative molecular weight, surface cracking of products, loss of gloss, and more serious is that the mechanical properties such as impact strength, tensile strength and elongation are significantly reduced, It even loses its 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, which can lead to the end of the service life of materials and a large number of waste, resulting in a great waste of resources and serious environmental pollution.

Aging classification of polymer materials

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 lines, cracks, etc.

(2) Changes in physical properties. Such as changes in quality, size, heat resistance, cold resistance and other performance indicators.

(3) Changes in mechanical properties. Such as changes in tensile, bending 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 occur in use, it will inevitably cause economic losses, and even environmental damage, personal injury and death accidents, etc.

Therefore, it is necessary to replace the polymer material products before aging and failure. In the principle of energy conservation, low carbon and ecological development, as well as maximizing the function of polymer products, 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, and are widely used in the electronic industry, such as electrical machinery or electric tool housings, tuning parts for electrical appliances, machine housings, automotive engine blades, etc.

However, as the basic raw material of electronic devices, it is required that not only the mechanical strength should be kept good, but also the appearance and color of products should not change 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 devices will be affected.

PA6 and PA66 materials used as indoor electronic appliances will face high local temperature in actual use, so long-term thermal effect is one of the important factors that make PA6 and PA66 aging; Under the actual use environment and conditions, oxygen will participate in the aging process of nylon in most cases, and the joint action of heat and oxygen will greatly accelerate its aging process. Therefore, it is 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 thermal aging resistance of PA materials and greatly extend the service life of the materials.

Commonly used reinforced nylon has thermal oxygen stabilizer, including copper stabilizer, amine and hindered phenol antioxidant, hydroperoxide decomposer, etc.

According to some data 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 good ultraviolet absorber, so black reinforced nylon material is more resistant to aging than other color reinforced nylon materials.

It has been found that POE-g-MAH elastomer can resist thermal aging to some extent in the toughened PA6 system. The combination of antioxidant 1098 and phosphite antioxidant 626 has synergistic effect in PA6 system.

Copper salt antioxidant, antioxidant 1098 and their composite antioxidants are all high effective antioxidants of PA6 resin system. Copper salt antioxidant has more obvious anti-aging effect on toughened PA6 system. The blending system of antioxidant 1010 has limited anti-aging effect on PA6 resin. Reinforced nylon and copper salt antioxidant and 1098 composite antioxidant toughened PA6 material can meet the thermal oxidation aging requirements of the material.