What are the requirements for the performance of plastic antioxidants?
Antioxidant is one of the additives commonly used in plastic materials. When it is only present in a small amount in plastics, it can delay or inhibit the action of oxygen, ozone, etc. in the process of polymerization, storage, transportation, processing and use. The process of degradation, which prevents the material from aging and significantly extends its useful life. However, due to the different chemical structures of different plastics, different processing and molding process temperatures, and different safety requirements of the final product, all of which affect the selection of antioxidants. Then, when selecting an antioxidant, the antioxidants involved should have the following application characteristics.
At present, the most widely used antioxidants in the plastics industry are mainly amines and hindered phenolic antioxidants. Among them, amine antioxidants are mainly used in black rubber products, while hindered phenol antioxidants are caused by The color stain is smaller and more applied to light-colored plastic products. In fact, hindered phenolic antioxidants can also cause coloring, which is characterized by yellowing or redness, usually caused by oxidation products of hindered phenolic antioxidants. By properly selecting phenolic antioxidants and other ancillary antioxidants, color contamination can be avoided or reduced.
The processing temperature of different plastics is different from the ambient temperature. At this time, excellent heat resistance stability becomes an important indicator of antioxidants for plastics. The heat resistance of antioxidants is good, and plastics due to thermal decomposition can be prevented. Color change or reduction in antioxidant performance, especially for plastics that require higher molding temperatures, the need for high temperature resistance of antioxidants.
Migration resistance and compatibility
The migration resistance of antioxidants and their compatibility with plastics are closely related, and the compatibility depends to a large extent on the binding force between antioxidants and plastics, such as polarity closeness and solubility parameter closeness. and many more. If the compatibility between the antioxidant and the plastic is too poor, the antioxidant can easily migrate out of the plastic, and a so-called "blooming" phenomenon occurs. Since the role of the antioxidant is to protect the plastic as a whole, the excessively rapid migration will lead to a decrease in the anti-aging properties of the plastic in addition to the blooming, especially for those plastics that require long-term resistance to thermal aging. in this way. In addition, highly crystalline plastics are more prone to migration of additives such as antioxidants.
Antagonism with other ingredients
When the antioxidant is added to the plastic, the last thing we want to happen is that it is "corresponding" to other components in the plastic, that is, it has an antagonistic effect, and it is more desirable to obtain strong + strong = stronger, that is, synergistic effect. For peroxide cross-linked polyethylene cables, there is an antagonistic effect between the peroxide cross-linking agent and the antioxidant. Inappropriate antioxidant varieties and dosages will ultimately affect the quality of the cable material. In the case of rubber cross-linking, improper antioxidants may significantly delay the cross-linking or solidification of the rubber, and even affect its cross-linking density.
Only the antioxidants are evenly dispersed in the plastic to ensure the overall anti-aging properties of the plastic, especially for thin products. The lack of antioxidants in some areas of thin products will become the weak point of the entire product, and will be destroyed first, leading to the early failure of the entire product. In order to ensure the quality, the industry basically adds antioxidants through the masterbatch form to ensure Antioxidants are as evenly dispersed as possible in thin articles.
Safety and hygiene
Some antioxidants can cause harm to people's health, such as bisphenol A. Different limits are set for different countries for the amount of antioxidants allowed. Especially in food packaging, the antioxidant can be added as much as possible, and it needs to be added as little as possible, as long as it meets its processing requirements. At the same time, the quality of antioxidants from different manufacturers is not the same, such as insufficient purity, heavy metals and so on.
Value for money
Cost is the first factor considered by most companies, especially for the plastics modification industry with low profit margins. This also leads to some excellent antioxidant varieties that are too big to be able to flex their muscles. However, it should be reminded that anti-oxidant users should not only focus on the price point. Through the combination of antioxidants with different advantages, those expensive antioxidants are still useful. We will eventually see it. It is a comprehensive cost. In the future plastics industry, the quality requirements for products will only be higher and higher, and good antioxidants will eventually win the hearts of users.