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Antioxidants: The Polymer Additives that Defend Materials Against Oxidation

Oxygen is an awesome element. It’s essential for life, fuels combustion reactions that drive our cars and warm our houses, and makes up about 21 percent of Earth’s atmosphere. But it’s also one of the most corrosive elements in the universe. That’s because oxygen has a way of coaxing electrons away from a number of different molecules — the underlying principle of oxidation.

Many everyday things are subject to oxidation. It’s why your silverware turns green, apples and avocadoes become brown when cut, and metal garden tools rust when left unprotected outside. Exposure to oxygen leads to molecular changes that cause visible differences in the items made from the oxidized material. The same thing happens to polymers, and when it does the consequences can be far more noteworthy than discoloration — although that is one result.

Because polymer molecules are very large, they’re a prime target for oxygen to woo away those important electrons. In fact, oxygen is a major cause of polymer failure. When oxidation occurs in polymers, the items made from the materials can break, shatter, bend, warp and undergo a host of undesirable chemical changes. If oxidation occurs in a polymer used to make a critical product, such as a medical device or a structural support for a building or bridge, the failure can be catastrophic.

Enter antioxidants, the polymer additives that are the great defenders against oxygenation. Antioxidants block or halt the chain reaction of oxidation, and help a material retain the qualities it’s been designed for. It can help preserve a polymer’s color, elasticity or rigidity (depending on what’s needed), as well as its strength and chemical composition.

A variety of substances can function as antioxidants in polymers, and which one works best for a given material depends on many factors, including the ultimate function of the item that will be made from the polymer. For example, maticamines and sterically hindered phenols are often used as antioxidants in products made from rubber, while monocylic and polycylic phenols can protect polyblends from oxidation. Because oxygen also plays a role in many other forms of polymer degradation, antioxidants may appear in concert with other stabilizing additives, too.

Of course, any time you’re working with such a cocktail of elements, anything can happen. When a material isn’t behaving as desired, oxygen stabilizers are one of the additives to look at. Additives analysis can determine the type, presence and quantity of antioxidant in a given material, and help predict if products made from that polymer will perform as expected.

Ultimately, working with polymers is a balancing act, and antioxidants are the type of polymer additive that helps ensure electrons stay put and don’t go kiting off due to oxidation. Antioxidants strike that perfect balance between the oxygen we need and the negative oxidation that we don’t.