The ion exchange resin matrix is made of hydrocarbon chains that are cross-linked to each other, a process called polymerization. The cross-linking gives the resin polymer a stronger, more resilient structure and greater capacity (volume). While the chemical composition of most ion exchange resins is polystyrene, some types of resins are made from acrylic acid (acrylonitrile or methyl acrylate). The resin polymer is then treated with one or more chemical treatments that incorporate functional groups into the ion exchange sites throughout the matrix. These functional groups give the ion exchange resin its separation capabilities and can vary greatly from resin type to resin type.
The most common compositions include:
Strong Acid Cation Exchange Resins:
Strong acid cation exchange resins consist of a polystyrene matrix and sulfonate (SO3-) functional groups that can carry sodium ions (Na2+) for softening applications or hydrogen ions (H+) for demineralization
Weak Acid Cation Exchange Resins:
Weak acid cation exchange resins consist of acrylic acid polymers that have been hydrolyzed with sulfuric acid or caustic soda to produce carboxylic acid functional groups. Due to their high affinity for hydrogen ions (H+), WAC resins are often used to selectively remove cations associated with alkalinity.
