cross linking

Crosslinking

Crosslinking is when individual polymer chains are linked together by covalent bonds to form one giant molecule.

Emulsion Polymerization:-

A mixture in which two immiscible substances, like oil and water, stay mixed together thanks to a third substance called an emulsifier. The emulsifier is usually something like a soap, whose molecules have a water-soluble end and an organic-soluble end. The soap molecules form little balls called micelles, in which the water-soluble ends point out into the water, and the organic-soluble ends point into the inside of the ball. The oil is stabilized in the water by hiding in the center of the micelle. Thus the water and oil stay mixed.

Function Of The Reactants

·        Sodium Lauryl Sulphate:-

Soap a molecule in which one end is polar and water-soluble and the other end is non-polar and organic-soluble, such as sodium lauryl sulfate:

These form micelles in water, little balls in which the polar ends of the molecules point out into the water, and the non-polar ends point inward, away from the water. Water insoluble dirt can hide inside the micelle, so soapy water washes away dirt that plain water can't.

·        Hydroxyethyl Acrylate:-

Hydroxyethyl Acrylate gives hydroxyl functional groups to an acrylic polymer backbone. The hydroxyl groups act as crosslinking sites for hydrophilicity, improving adhesion and resistance against corrosion, fogging and abrasion. End applications include adhesives, coatings, sealants and thermosetting paints. It is also used in additives for personal care products.

·        Potassium Persulphate:-

Both thermal and redox generation of free radicals have been used in emulsion polymerization. Persulfate salts are commonly used in both initiation modes. The persulfate ion readily breaks up into sulfate radical ions above about 50°C, providing a thermal source of initiation. Redox initiation takes place when an oxidant such as a persulfate salt, a reducing agent such as glucose, Rongalite, or sulfite, and a redox catalyst such as an iron compound are all included in the polymerization recipe. Redox recipes are not limited by temperature and are used for polymerizations that take place below 50°C.

Although organic peroxides and hydro peroxides are used in emulsion polymerization, initiators are usually water soluble and partition into the water phase. This enables the particle generation behavior described in the theory section. In redox initiation, either the oxidant or the reducing agent (or both) must be water soluble, but one component can be water-insoluble.

·        Sodium Metabisulfite:-

It has been found that the system diazonium salt/sodium Metabisulfite (Na₂S₂O₅) is an effective one for the initiation of polymerization of an aqueous solution.

·        Sequestrene:-

A series of complexing agents and metal complexes consisting of ethylenediaminetetraacetic acid and salts. It is acting as an anti-coagulating agent.