Antioxidants: How to select stabilizers for polyolefins (PP, PE)?
Last update on Jul 20, 2026
Polyolefins like polyethylene (PE) and polypropylene (PP) are versatile and low-cost polymers. However, they are inherently vulnerable to thermo-oxidative degradation. Heat, oxygen, shear, and UV exposure trigger free radical reactions. This, in turn, leads to polymer deterioration.
Antioxidants are the primary defense, working through two complementary mechanisms.
- Primary antioxidants that scavenge free radicals directly
- Secondary antioxidants that decompose hydroperoxides before they propagate further degradation.
Choosing the right combination and ratio of these stabilizers, tailored to the polymer type, catalyst system, and end application, is what determines whether a polyolefin part holds up in processing and over its service life.
In this guide, we will break down the antioxidant chemistries, synergies, and starting-point formulations for PP, HDPE, and LLDPE so that you select the right additive for your next formulation.
How to stabilize polyolefins?
Polyolefins, such as polyethylene (PE) and polypropylene (PP), are susceptible to thermo-oxidative degradation during processing and throughout their service life. Heat, oxygen, shear stress, and UV exposure generate free radicals. This can lead to chain scission, discoloration, embrittlement, loss of mechanical properties, and reduced product lifespan.
Antioxidants help stabilize polyolefins by preventing their oxidation during:
- High-temperature extrusion, injection molding, and blow molding
- Pelletizing and compounding
- Long-term thermal aging
- Outdoor weathering (combined with UV exposure)
- Multiple recycling and reprocessing cycles
Selecting the right antioxidant package is therefore critical to maintaining polymer performance from processing to end use. Our master catalog eases this selection process with its advanced filters and easy-to-use sampling and comparison options.
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Primary antioxidants
Primary antioxidants interrupt the oxidation chain reaction by neutralizing free radicals. Common chemistries include hindered phenols and aromatic amines.
Benefits: Excellent long-term thermal stability, color protection, retention of mechanical properties, and effective during product use.
Applications: Packaging, automotive components, consumer goods and household appliances.
Secondary antioxidants
Secondary antioxidants decompose hydroperoxides before they generate additional free radicals. Common chemistries include phosphites, phosphonites, and thioesters.
Benefits: Improved melt processing stability, lower color formation during processing, better melt flow consistency, and reduced polymer degradation at high temperatures.
Applications: High-temperature extrusion, fiber spinning, film production, and injection molding.
The effectiveness of an antioxidant package ultimately depends on the polymer and application. Let's now examine how antioxidants are selected and combined to stabilize polypropylene.