Working Mechanism of Stabilizers

The basic mechanism of stabilizer involves the stabilization of chemical reactions by inhibiting the reaction or slowing down the reaction.

Anti-oxidants

Oxidation reactions can produce free radicals. In turn, these radicals can start chain reactions. When the chain reaction occurs in a cell, it can cause damage or death
to the cell. Antioxidants terminate these chain reactions by removing free radical intermediates, and inhibit other oxidation reactions.

1. Antioxidants do this by being oxidized themselves, so antioxidants are often reducing agents such as thiols, ascorbic acid, or polyphenols, or
2. Antioxidants may directly react with the reactive radicals to destroy them by accepting or donating electron(s) to eliminate the unpaired condition of the radical, or
3. They may indirectly decrease the formation of free radicals by inhibiting the activities or expressions of free radical generating enzymes or by enhancing the activities and expressions of other antioxidant enzymes.

Hydrogen Peroxide Bleach Stabilizer

Sodium silicates are the most commonly used and most effective hydrogen peroxide bleach stabilizers. They may be used as colloidal silicate (water glass), ortho silicate or metasilicate.
The mechanism by which hydrogen peroxide bleach stabilizer stabilize is not completely understood, however it is known that silicates have a natural affinity for ferrous ions and ferrous ions are naturally present in cotton. Hydrogen peroxide is a weak acid and ionizes in water to form a hydrogen ion and per hydroxyl ion which is an active bleaching species.
H₂O₂ + H₂0 → H⁺ + OOH^-

This reaction is catalyzed by metal ions such as ferrous ions. This reaction is not desired as it is ineffective use of peroxide and causes fibre damage.
H₂O₂ + H₂0 → H₂O + ½ O₂

It is possible that the silicates are adsorbed onto the ferrous ions in the fibre, producing a species that catalytically enhances bleaching while reducing bleach decomposition and fibre damage. Stabilization is enhanced by the presence of magnesium ions. Magnesium serves as a pH buffer. As the concentration of OOH^- rises during bleaching, magnesium hydroxide (Mg(OH)₂) precipitates, reducing the OOH^- concentration. Bleach solutions containing only magnesium ions have good stability but the bleaching effectiveness is not as good as when silicates are included.
Magnesium salts can be used in textile bleaching as pH buffers. It is used in hydrogen peroxide bleaching as pH buffers.

Sequestering Agents

Sequestering agents work by a mechanism of complex formation, often in the form of chelation. Sequestering agents or Chelating agents remove a metal ion to from a solution system by forming a complex ion that does not have the chemical reactions of the ion that is removed.
A chelating agent contains substituents suitably located to form one or more chelate rings by electron donation to the metal ion, the resulting complex remaining soluble under the conditions of processing.
The most useful donating atoms are nitrogen, as found in amines or substituted amines, and oxygen in the form of carboxyl, phosphate or ionized hydroxyl groups.

Emulsifier

There are 3 kinds of mechanisms by which emulsifier stabilizes the emulsion;
Surface tension theory – according to this theory, emulsification takes place by reduction of interfacial tension between two phases.
Repulsion theory – the emulsifying agent creates a film over one phase that forms globules, which repel each other. This repulsive force causes them to remain suspended in the dispersion medium.
Viscosity modification – emulgents like acacia and tragacanth, which are hydrocolloids, as well as PEG (or polyethylene glycol), glycerin, and other polymers like CMC (carboxymethyl cellulose), all increase the viscosity of the medium, which helps create and maintain the suspension of globules of dispersed phase.