Antioxidant Masterbatch
Antioxidant Masterbatch
Plastics are susceptible to thermo oxidative degradation during process and usage. This may be because of higher temperatures, high shear rates or under the effects of light & oxygen. This will cause:
- Loss of strength.
- Loss in elongation
- Surface may become rough and less glossy
- Color fading or discoloration
Oxidation is a chain reaction process involving free radical and hydroperoxide intermediates. Antioxidants decompose the free radicals by chemical reaction. Polymer manufacturers add antioxidant in certain polymer grades but this will not be sufficient to withstand number of processing cycles, higher shear or temperature. This results in degradation of polymer thereby deteriorating mechanical properties.
Different families of antioxidants are reactive with different intermediates in the oxidation process.
Two types of Antioxidant
Primary Antioxidants such as hindered phenols interrupt the primary oxidation cycle by removing the propagating radicals. Aromatic amines tend to discolour the end product and hence their use in plastics is limited. Phenolic antioxidants are commonly used in most of the polymers. Phenolic antioxidants protect plastics or other polymers against degradation and oxidation at high processing temperatures.
These type of Antioxidants stops degradation by preventing the generation of free radicals. Any biproducts produced by the hydroperoxide decomposition are transferred in to non-reactive thermally stable products. Commonly used secondary Antioxidants having either Phosphites or phosphonite groups or Organic Sulphur containing compounds and dithiophosphonates are widely used.
Selection of Antioxidants depends on a number of factors.
Selection of Antioxidants depends on a number of factors.
Selection of Antioxidants depends on a number of factors.
The Efficiency of an antioxidant n polymers is determined by three processes :
The chemical reactivity, The physical loss and a minimal effective concentration. Uniformity and dispersion depends upon processing and also the ability of the additive to reach the polymer’s attacked sites by diffusing through the viscous melt. Combination of antioxidant additives are always preferred for protection at different levels of processing and even in service life.
Antioxidant Masterbatches help you combat the degradation of plastic due do oxygen and heat. The antioxidant systems suitable for various polymers are selected considering the end applications. For example Antioxidants added in agricultural films to improve thermal stability, prevents discoloration and maintains transparency.