Product Group Antioxidants of BASF Plastic Additives
Plastics & Rubber
BASF Plastic Additives
BASF Plastic Additives Products
Antioxidants

Plastics & Rubber

Antioxidants

Virtually all polymeric materials undergo oxidation reactions. Oxidation can occur at every stage of the life cycle of a polymer, i.e. during manufacturing and storage of the material or during processing and end-use.

Typical manifestations of oxidation of polymers can be change of viscosity during processing, appearance, and loss of mechanical properties such as elongation, impact strength, tensile strength, and flexibility. Antioxidants protect polymers against oxidation by controlling molecular weight changes that lead to a loss of physical, mechanical, and optical properties.

Among other factors heat, light and mechanical stress can result in the degradation of the polymer.

Antioxidants interrupt the degradation processes in different ways, depending on their structure. The two major classifications are: chain terminating primary antioxidants and hydroperoxide decomposing secondary antioxidants.

Primary antioxidants

Primary antioxidants react rapidly with free radicals and are, therefore, called "Radical Scavengers" and are mainly used for extrusion processing. Scavenging the radicals immediately stops degradation. The majority of primary antioxidants for polymers are sterically hindered phenols. Irganox® E 201 and the blend Irgastab® FS 301 belong to this class of antioxidants.

Part of primary antioxidants, are aromatic amines, mainly used in carbon-black filled rubbers and some polyurethane applications. Irganox® 5057 is such an aromatic amine for polyol and rubber stabilization.

Secondary antioxidants

Secondary antioxidants, including phosphites and thioesters, react with hydroperoxides to yield non-radical products. They are particularly useful in synergistic combinations with primary antioxidants.

Phosphites are most effective during processing and protect both the polymer and the primary antioxidant.

Thioesters are useful in increasing the long-term thermal stability in conjunction with phenolic antioxidants. Irgafos® 168, Irgafos® 126, Irganox® PS 800 and Irganox® PS 802 are secondary antioxidants. 

Multifunctional stabilizers

In multifunctional stabilizers, several functions are combined in the same molecule: the most widely used combination are sterically hindered phenols with sulfur substituents or sterically hindered phenols with copper chelating function (metal deactivators). Irganox® 1035, Irganox® 565, Irganox® 1520 L, Irganox® MD 1024 are examples of multifunctional additives.