Antioxidants are the core anti-aging agents for plastics, which eliminate free radicals, decompose hydrogen peroxides, passivate metal ions, block oxidative degradation, avoid plastic discoloration and brittleness, and extend the service life. For example, adding antioxidants to PP outdoor products can extend the service life from 3 months to 3-5 years. The mainstream types are divided into four categories: hindered phenols (such as 1010), low toxicity and universal, suitable for PE/PP/PET; Phosphorous esters (such as 168) are resistant to high temperatures and are often compounded with hindered phenols; Sulfides such as DLTP are efficient at low temperatures and suitable for polyolefins; Targeted metal ion passivators prevent catalytic degradation. In terms of application, PE agricultural film uses 1076+DLTP, PET beverage bottles add 1010+168, and PP meal boxes choose low migration 1010. The current upgrade towards high molecular weight, bio based, and multifunctional directions is the key guarantee for the long-term durability of plastics.

Heat stabilizers are the core additives in plastic processing and use, which can inhibit the degradation of plastics caused by high temperature, oxygen, and light, avoid discoloration and brittleness, and ensure product quality. They are especially indispensable for PVC (without stabilizers, HCl will be released and degraded during processing). The mainstream types are divided into five categories: lead salts have strong heat resistance and are suitable for PVC pipes; Metal soaps (such as calcium zinc composite soaps) are low toxic and suitable for food grade PVC; Organic tin based high-efficiency, used for high-end PVC; Rare earth environmental protection, suitable for multiple plastics; Organic auxiliary stabilizers need to be compounded to improve efficiency. In terms of application, lead salts are added to PVC drainage pipes, calcium zinc composite soap is used for food packaging films, hindered phenol is added to PE water supply pipes, and hypophosphite is added to PET bottles. The current upgrade towards lead-free, multifunctional, and bio based direction is a key guarantee for plastic quality.

Plasticizers are key additives for optimizing the performance of PET, which can overcome the shortcomings of high brittleness, poor processing flowability, and weak low-temperature impact resistance of native PET. By weakening the intermolecular forces of PET, the glass transition temperature and crystallinity are reduced, endowing it with flexibility, processability, and low-temperature adaptability. Common types are divided into four categories: epoxy (such as ESO), low migration, safe, suitable for food/pharmaceutical PET packaging; Fatty dicarboxylic acid esters (such as DOS) enhance low-temperature impact resistance and are used for freezing PET films; Phosphates (such as TOP) have both flame retardancy and temperature resistance, making them suitable for PET engineering plastics; Polyester products (such as PPA) with long-term low migration, used for PET products with long-term use. In applications, it is necessary to balance functionality and safety. Currently, there is an upgrade towards low toxicity and low migration directions such as bio based and reactive materials, which play an irreplaceable optimization role in multiple fields of PET.