Polymer Material Aging Mechanism

The general mechanism of polymer aging is mainly thermal oxidative aging and photooxygen aging. The reaction mechanism is generally the same as that of low-molecular-weight compounds, and both have the characteristics of automatic catalytic oxidation reaction.

In order to increase the anti-aging performance of plastic products, a certain degree of anti-aging agent should also be added to the formula when plastic is rapidly formed. Now generally speaking, the plastics we buy have been added with antioxidants. And because of the different uses of plastic products, the antioxidants required for plastic products are also different. Therefore, when plastics are synthesized, the antioxidants are not used alone, but they can cooperate with each other to obtain good antioxidant effects. Therefore, how to choose an antioxidant has become a difficult problem. The antioxidant must first be compatible with the polymer, and its volatility should be small. In addition, it should not be colored as much as possible to avoid destroying the original color of plastic products. In addition, it must meet the standards of non-toxic, odorless and tasteless. After the plastic is formed, methods such as applying a protective period contact layer can be used to minimize the aging of plastic products.

The mechanism of thermal oxygen aging is generally considered to be a free radical reaction. The direct action of polymers and oxygen can also form highly active alkyl radicals. In the presence of oxygen, the formed radicals will react with oxygen to form hydroperoxides and simultaneously form a new radical. Hydroperoxides have an autocatalytic effect on the oxidation reaction. Through further chain growth, chain transfer or chain termination reactions, the polymer chains are broken or crosslinked.

Photooxidative aging is generally considered to be a random degradation process. As a result of aging, the molecular weight of the polymer decreases rapidly. The photo-oxidative aging process of polymer materials is a combination of free radical reactions and non-radical reactions. The carbonyl group in the organic aliphatic carbonyl compound is the main initiating group for the photochemical reaction of polypropylene.

Polypropylene materials are very prone to photothermal oxygen aging. If no auxiliary agents such as antioxidants are added and placed outdoors, their basic physical and mechanical properties will be significantly reduced in a short time. Therefore, if you want to use it outdoors, you must find ways to improve its resistance to photothermal oxygen aging. Modification of photo-oxidation resistance of polypropylene to improve its ability to resist photo-oxidation and aging, so that it has better outdoor adaptability. Therefore, the research on the anti-aging of polypropylene has become a main research direction of polypropylene (PP), and it will be paid more and more attention in the future.