In the lifecycle of polymers (such as polyethylene PE, polypropylene PP, engineering plastics, etc.), thermal-oxidative degradation is always the "invisible killer" threatening product performance. Whether in the processing stage of high-temperature extrusion or during long-term use, polymer molecular chains are affected by heat and oxygen.

As a world-class global supplier of polymer additives, Onelead has been committed for more than 20 years to providing customers with efficient polymer protection solutions through precise antioxidant systems. This article will delve into the "synergistic effect" of antioxidants and its core role in processing.

1. Mechanism of Polymer Degradation: Free Radical Chain Reaction

Polymer degradation is a complex auto-oxidation process. When resin is heated during processing or subjected to mechanical shear, molecular chains break to produce free radicals (R·). These free radicals react with oxygen to generate peroxy radicals (ROO·), which then abstract hydrogen from the polymer chain to form hydroperoxides (ROOH).

If left un-intervened, this process will cycle repeatedly like a snowball, eventually leading to:

Abnormal changes in Melt Flow Rate (MFR): Molecular chain scission or cross-linking.

Decline in mechanical properties: Becoming brittle or cracking.

Appearance deterioration: Yellowing and loss of luster.

2. The "Synergistic Effect" of Primary and Secondary Antioxidants

In industrial practice, a single type of antioxidant is often difficult to cope with complex degradation environments. A "1+1 > 2" synergistic system is currently the mainstream solution.

Primary Antioxidants: Hindered Phenols

Representative Products: Leadstab AO 1010, Leadstab AO 1076

Mechanism: Known as "free radical scavengers." They provide active hydrogen atoms to react first with peroxy radicals, converting them into a stable state and thus terminating the chain reaction. They primarily provide long-term thermal stability.

Secondary Antioxidants: Phosphites

Representative Products: Leadstab AO 168, Leadstab AO 9228

Mechanism: Known as "hydroperoxide decomposers." They decompose the already generated hydroperoxides (ROOH) during the processing stage, converting them into harmless alcohols. They primarily provide processing stability and prevent discoloration during processing.