Why Use Organic Peroxides?

Understanding organic peroxides

Organic peroxides are organic compounds that contain an -O-O- peroxide functional group, where the hydrogen atoms in hydrogen peroxide are replaced by alkyl, acyl, or aromatic groups. They are characterized by the production of oxygen free radicals upon heating beyond a certain temperature, leading to instability and easy decomposition. The organic peroxides produced in the chemical industry are mainly used as polymerization initiators and catalysts for synthetic resins. In the field of polymer materials, organic peroxides can be used as initiators for free radical polymerization, initiators for grafting reactions, crosslinking agents for rubber and plastics, curing agents for unsaturated polyesters, and molecular weight and molecular weight distribution regulators for the preparation of spun polypropylene. Polluted air in the environment can produce peroxy acyl nitrates through free radical reactions under light, which is one of the particulate species in photochemical oxidants. They are strongly irritating to the skin, eyes, and mucous membranes and are important air pollutants. These substances are considered flammable and explosive hazardous materials, and safety precautions should be taken when using them. Generally, the active oxygen content, activation energy, half-life, and decomposition temperature are the basic criteria for selection. All organic peroxides are thermally unstable and their decomposition rates increase with increasing temperature.

Reasons for using organic peroxides

We all know that some chemical products cannot be produced without organic peroxides. So why do we use organic peroxides? Rubber or some polyolefin materials can obtain the required mechanical, thermal, or chemical properties through cross-linking reactions. Depending on the polymer and application, this reaction can also be called curing (especially for thermosetting materials) or sulfur vulcanization (especially for rubber and those containing sulfur).

Among these different cross-linking reactions, the most common are free radical chemical reactions. The first step is generally the generation of a free radical. Organic peroxides serve as a source of free radicals. They generate highly active peroxide free radicals through thermal decomposition and can capture hydrogen atoms on the polymer backbone, especially those containing a fatty CH2 unit. These large molecular free radicals then undergo branching and cross-linking reactions to recombine. Organic peroxides can be used alone or in combination with multifunctional free radical monomers. In rubber, peroxide cross-linking does not produce nitrosamines and can effectively replace traditional vulcanization systems.