WHITENERS
Optical Brightening Agents (OBA) or Fluorescent Whitening Agents (FWA) is added to many substrates to Reduce Yellowing, Improve Whiteness and Enhance the Brightness of the product. Optical whiteners function by absorbing ultraviolet radiation and re-emitting blue light. The emitted blue light will reduce the yellow color of the substrate and impart a pleasing whiter-than-white appearance. Optical brighteners give more intensity to some colours as well.
THERE ARE 3 DIFFERENT TYPES OF OBA / FWA BASED ON THE SULFONIC ACID GROUP :
I. DISULFONIC / DIVALENT
It is a constituent of Two Sulfonic Acid groups and is good for hydrophobic fiber (Nylon, Silk and Wool) application in Acidic pH.
II. TETRASULFONIC / TETRAVALENT
It is a constituent of Four Sulfonic Acid groups and is having good solubility and is ideal for Cellulosic fiber and Paper application at Neutral or Alkaline pH.
III. HEXASULFONIC / HEXAVALENT
It is a constituent of Six Sulfonic Acid groups and has excellent solubility for Surface Coating applications like Photographic Paper etc.