Canning and Fish Packaging Technology

Unit 12 - Additives in plastics

12.1.2.Antioxidants
Many plastics are subjected to pick up of oxygen with subsequent decomposition. The hazards may be in long term usage or during processing. Other factors which accelerate oxidative decomposition are high temperature, metal ions and U.V rays. The effect of oxidation may result in the formation of simple and small compounds as in fat oxidation. In order to prevent this type of oxidation, antioxidants are added. The requirement of an ideal anti oxidant may be summarized as follows.

• Must be permanent.
• Capable of inhibiting oxidation under all conditions.
• Must be non-blooming
• They must not discolour.
• They must not adversely affect the characteristic properties of the base polymer.
• Must be non toxic and colourless.

Some of the compounds added as antioxidants are phenols (BHA, BHT) and organic sulphides.