Abstract

The absorption of short-wavelength light (violet-to-blue) results in a yellow cast to fabrics. Fluorescent whitening agents (FWAs) absorb the invisible uv portion of the daylight spectrum and convert this energy into the longer-wavelength visible portion of the spectrum, ie, into blue to blue-violet light. This can be used to replace the light lost through absorption, thereby attaining a neutral, complete white.

Fluorescent whitening agents in use in the 1990s are aromatic or heterocyclic compounds; many contain condensed ring systems. Almost all of these compounds are derivatives of stilbene or 4,4¢-diaminostilbene; biphenyl; five-membered heterocycles, eg, triazoles, oxazoles, etc; or six-membered heterocycles, eg, coumarins, naphthalimide, etc.

Fluorescent whitening agents find use in the textile, paper, and synthetic fiber and plastics industries.