Plastics are susceptible to ageing and yellowing over time. Also recycled plastics tend to yellow after repeated heat histories and shear mechanisms. Optical brighteners help to hide the ageing / yellowing characteristics of plastics as they increase the brightness and gloss of plastics. They act on fluorescence mechanism i.e. they absorb light in UV range of 340 – 370 nm and re-emit that light in blue wavelengths of visible spectrum i.e. 420 – 470 nm.
Optical brighteners are typically used in recycled PE and PP applications as well as virgin films and fibres to improve colour, gloss and brightness and to hide yellowness.