Requirements for the Application of Antioxidants in Plastics

Release date:

2025-04-03

Antioxidants are one of the commonly used additives in plastic materials, helping to prevent material degradation and significantly extending their service life. However, due to various limitations—such as differences in the chemical structures of different plastics, varying processing temperatures during molding, and diverse safety requirements for the finished products—the selection of this product is often affected. Therefore, when choosing this product, it’s essential to consider the following application-specific characteristics.
1. Color Stainability
Currently, the two main categories of antioxidants widely used in the plastics industry are amine-based and hindered phenol antioxidants. Among these, amine antioxidants are primarily employed in black rubber products, while hindered phenol antioxidants are more commonly used in light-colored plastic products due to their minimal tendency to cause discoloration. In fact, hindered phenol antioxidants can still lead to slight color staining—typically manifesting as yellowing or reddening—which is usually caused by oxidation products of the antioxidants themselves. By carefully selecting appropriate phenolic antioxidants along with other complementary antioxidant additives, it’s possible to effectively prevent or minimize such discoloration issues.
2. Heat Resistance Stability
Different plastics have varying processing and service temperatures. In such cases, excellent thermal stability becomes a critical indicator for antioxidant additives used in plastics. A well-performing antioxidant with good thermal stability can prevent color changes or reduced antioxidant efficacy caused by its thermal decomposition during processing—especially for plastics that require higher molding temperatures, where the demand for high-temperature resistance in antioxidants is steadily increasing.
3. Migration Resistance and Compatibility
The migration resistance of antioxidants is closely linked to their compatibility with plastics, and this compatibility largely depends on the strength of the interaction between the antioxidant and the plastic—factors such as polarity similarity and solubility parameter compatibility play crucial roles. If the compatibility between the antioxidant and the plastic is too poor, the antioxidant will readily migrate out of the plastic, leading to the so-called "blooming" phenomenon. Since antioxidants are designed to provide comprehensive protection for plastics, excessively rapid migration not only causes blooming but also undermines the material's long-term anti-aging performance, particularly in plastics that require sustained resistance to thermo-oxidative degradation. Moreover, highly crystalline plastics are more prone to the migration of additives like antioxidants.
4. Antagonism with Other Ingredients
When antioxidants are added to plastics, what we absolutely want to avoid is their "antagonism" with other components in the plastic—meaning they counteract each other's effects. Instead, we ideally aim for a scenario where "strong + strong = even stronger," resulting in synergistic interactions. For instance, in peroxide-crosslinked polyethylene cables, there’s often an antagonistic relationship between the peroxide crosslinking agent and the antioxidant. Improper selection or dosage of the antioxidant can ultimately compromise the quality of the cable material. Similarly, during rubber vulcanization, using an unsuitable antioxidant may significantly slow down the crosslinking or curing process—and in some cases, even disrupt the desired crosslink density altogether.
5. Dispersion
Only when antioxidants are uniformly dispersed throughout the plastic can the material's overall resistance to aging be guaranteed—especially in the case of thin products. If certain areas of a thin product lack antioxidants, these regions become weak points that fail first, ultimately leading to premature failure of the entire product. To ensure consistent quality, the industry generally adds antioxidants in the form of masterbatches, ensuring that the antioxidants are as evenly distributed as possible within even the thinnest sections of the product.
6. Safety and Hygiene
Some antioxidants can pose health risks to humans, such as bisphenol A. Different countries have established varying limits on the allowable amounts of antioxidants that can be added. In particular, when it comes to food packaging, it’s best to avoid adding antioxidants altogether if possible—and if they must be used, keep the quantity to a minimum, as long as they adequately meet processing requirements. Meanwhile, the quality of antioxidants can vary significantly among different manufacturers, with issues like insufficient purity or excessive heavy metal content often being reported.
7. Cost-effectiveness
Cost is the primary factor most businesses consider, especially in the plastics modification industry, where profit margins are already thin. This often means that some high-performing antioxidant products, despite their superior performance, remain underutilized simply because of their high price. However, it’s important to remind antioxidant users not to focus solely on cost. By strategically combining antioxidants with complementary advantages, even the pricier options can still prove highly effective. Ultimately, what matters most is the overall cost-effectiveness. Looking ahead, the plastics industry will continue to demand ever-higher product quality, and in this competitive landscape, only the best antioxidant solutions—those that deliver both performance and value—will ultimately win over customers.