Types of Gels

Gels that exhibit elasticity are known as elastic gels, also called reversible gels. Elastic gels can be formed from a variety of substances, including starch, gelatin, and soap. The characteristics of elastic gels are summarized below.

• Gels formed from organic compounds are usually elastic gels.
• After heating (dehydration), elastic gels form elastic solids.
• The original elastic gels can be obtained by adding water or liquid to the elastic solids.
• When a force is applied, elastic gels change shape, but when the force is released, they return to their previous shape.

Non-elastic gels, or irreversible gels, are gels that convert loose liquids into dry masses when heated, but do not return to their original form when they contact the liquid. They have a network of covalent bonds connected, giving them a rigid structure. Silica gels, solid alcohol, hydroxides of Fe, Al, Cr, etc. are common non-elastic gels. The characteristics of non-elastic gels are summarized below.

• Non-elastic gels are lyophobic.
• Non-elastic gels do not show imbibition.
• When a force is applied, the shape of non-elastic gels is irreversible.
• Gels made up of inorganic compounds are usually non-elastic gels.
• When heated (dehydrated), non-elastic gels form powders.
• The original non-elastic gels cannot be obtained by adding water or liquid to the powder.