Antioxidants for PP and PE: A Formulator's Guide

Polyolefins like polypropylene (PP) and polyethylene (PE) are inherently susceptible to thermo-oxidative degradation during melt processing at 200–280°C. Without adequate antioxidant protection, molecular weight drops sharply, leading to discoloration, embrittlement, and reduced service life.

Primary vs Secondary Antioxidants

Primary antioxidants (hindered phenols) scavenge peroxy radicals at the chain-propagation step. Common examples include Irganox 1010 (pentaerythritol-based tetrafunctional), Irganox 1076, and BHT for short-term protection.

Secondary antioxidants (phosphites and thioethers) decompose hydroperoxides before they generate more radicals. Irgafos 168 (tris(2,4-di-tert-butylphenyl) phosphite) is the industry standard for melt processing.

Synergistic Blending

The classic combination of Irganox 1010 (0.1–0.3%) + Irgafos 168 (0.1–0.5%) delivers 3–5× improvement in OIT (oxidation induction time) over single-component systems.

Dosage Recommendations

Application	Primary AO	Secondary AO	Total loading
Film extrusion (LDPE)	0.05–0.1%	0.1–0.15%	0.15–0.25%
Injection moulding (PP)	0.1–0.2%	0.2–0.3%	0.3–0.5%
Pipe extrusion (HDPE)	0.2–0.3%	0.3–0.5%	0.5–0.8%

Contact HMEChem for sample antioxidant packages tailored to your PP/PE grade.