Most polymers typically undergo oxidation, leading to degradation of the final product. To improve the quality of the final product, antioxidant plastic additives have been introduced into the plastics manufacturing process. In this article, let's learn how this powerful substance works and how it affects our plastics industry.
Plastic products, although durable and flexible, are always at risk of degradation throughout their life cycle due to a large number of environmental factors (e.g. oxygen, UV light, high temperatures ......). This is why the use of plastic additives plays an integral role in plastics manufacturing, of which antioxidant plastic additives are probably the most familiar name.
I. Antioxidants and their applications in the plastics industry
Antioxidant plastic additives are commonly used to prevent the negative effects of oxidation on plastic products. Oxidation is known to be a common phenomenon in which free radicals react with material molecules, thereby activating chemical chain reactions. This ultimately leads to the degradation of the product itself.
In the first stage, it occurs when oxygen is introduced into the molecular structure of the polymer, resulting in chemical chain reactions and permanent changes within the plastic, most typically a reduction in molecular weight. This process is accelerated in thermoforming (blown film, film cast, blow molding ......) and injection molding, which can lead to serious consequences such as degradation of the mechanical properties of the final product. To minimize these negative effects, antioxidant plastic additives must be added to the manufacturing process and used as process stabilizers to prevent oxidative conversion of plastic parts.
When it comes to another stage, the longer stage, antioxidant plastic additives are introduced to protect the final product from harmful environmental factors and to increase its service life. In addition, certain products are more susceptible to oxidation than others, which can be explained primarily by their plastic resins.
In general, plastic products that may contain antioxidant plastic additives include
Pipes and fittings for the construction industry: Since most of them are used outdoors and need to be exposed to external environmental factors for a long time, they are prone to oxidation. Therefore, it is very important to apply antioxidants to these.
Polyethylene (PE) films (used in the construction or food industries): While PE films are not the most affected by oxidation during their life cycle, they are most affected during the manufacturing process. Oxidation is the main factor causing mechanical degradation of PE films. Polypropylene (PP) products: Similarly, PP products also contain antioxidant plastic additives to protect the product from the negative effects of oxidation.
2. Common types of antioxidant plastic additives
As mentioned above, oxidation occurs in both phases of plastic products, which means that the use of antioxidant plastic additives corresponds to this. Basically, there are 3 main categories of such substances to perform specific functions.
Primary: This type is mainly used in the final product during its service life to protect itself from oxidation and other harmful environmental factors. Typically, the antioxidant plastic additives in this group are phenolic-based.
Secondary: Secondary antioxidant plastic additives serve as process stabilizers to protect the polymer from degradation due to oxidation during the manufacturing process, especially when the polymer is subjected to multiple thermal processing methods (blown film, injection molding, etc.). Typical chemicals used include phosphite or thioester.
Combination of primary and secondary: Not only are primary and secondary antioxidants used individually, they are also used in conjunction with each other to optimize the benefits obtained. In this way, plastic products are protected during processing steps and throughout their life cycle. This means that plastics manufacturers gain a lot of benefits because they provide a high quality output and end users are satisfied with a better lasting end product.
Depending on the characteristics of the end product and its use, plastics manufacturers can choose the right type of. For example, packaging products should use antioxidants during the manufacturing process because their oxidation occurs primarily during this process. Outdoor plastic products, on the other hand, should use both primary and secondary antioxidants in the manufacturing process and during their service life.