Antioxidants for Adhesives

Adhesives and their raw materials react like other organic materials with oxygen in a process called autoxidation. This guide offers you an extended overview of Antioxidants in the adhesives & sealant industry. You will be able to select the antioxidant you need from the different antioxidant families mentioned here. This guide will also take a look into antioxidant benefits and applications. You can also check how to test and determine the efficiency of the antioxidant(s) you have selected.

Primary Antioxidants

  1. Mechanism
  2. Hindered Phenols
  3. Secondary Aromatic Amines
  • Primary or free radical scavenging antioxidants inhibit oxidation via chain terminating reactions.
  • They have reactive OH or NH groups. (Hindered phenols and Secondary aromatic amines)
  • Inhibition occurs via a transfer of a proton to the free radical species.
  • The resulting radical is stable and does not abstract a proton from the polymer chain.

Hindered Phenols

Phenolic stabilizers are primary antioxidants that act as hydrogen donors. They react with peroxy radicals to form hydroperoxides and prevent the abstraction of hydrogen from the polymer backbone. Often used in combination with secondary antioxidants, phenolic stabilizers are offered in an extensive range of molecular weights, product forms, and functionalities.

Sterically hindered phenols, are the most widely used stabilizers of this type. They are effective during both processing and long term thermal aging and many have FDA approvals.

ROO* radicals are deactivated by hindered phenol via the following reaction.

The phenoxy radical generated are very stable due to their ability to build numerous mesomeric forms.

Secondary Aromatic Amines

Secondary aromatic amines act as primary antioxidants and are excellent hydrogen donors.

Secondary Aromatic Amines - Mechanism

Also available in an extensive range of molecular weights and product forms, aromatic amines are often more active than hindered phenols, because of less steric hinderance. Aromatic amines, however, are more discoloring than hindered phenols, especially on exposure to light or combustion gases (gas fade) and have limited FDA approvals.

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