Optical brighteners: all is not white that glitters

Short summary of the preceding: optical brighteners (fluorescents) are fluorescent molecules which absorb wavelengths of darker colours and remit lighter colours. This way colours turn brighter and vague stains are hushed up. The application in detergents are known and described in our earlier newsletters. Apart from fabric detergents there are yet other interesting applications for optical brighteners that are possibly inspiring for you as well.

Detergents
This is the best known application at most of our customers of both liquid and powder detergents.
The types CBS-X (stable in combination with bleach), DMS-X and AMS are common in washing powders and liquids. AMS is a less used type. It is comparable to DMS-X, but AMS has a higher intensity. The extinction (ratio remitted light versus absorbed light) of DMS-X is 360-440, and of AMS it is at 560. It therefore is a fact that the better fabric detergents make our clothing brighter and lace curtains and bed linen appear whiter.

Textile
Fluorsecents can also be applied directly onto textile fibres, so not only later through the use of detergents.
Standard optical brighteners enable a general bright colour effect. But safety jackets, for example, rely only on their red, orange or yellow signalling colours. A general fluorescent often tends too much in the blue direction. There are also special fluorescents which, on the contrary, tend towards yellow/red.
For other colour effects, there are fluorescents in the blue and violet directions.
And there are special fluorescents with optimum adhesion to cotton, cellulose or to synthetic fibres. All can be added to the manufacturing process of the fibres, or afterwards to the fabrics.

Plastics and coatings
Plastics and coatings are chemically comparable to synthetic textile fibres. Fluorescents which strengthen the colours of nylon, poly acrylic, polyester fibres, do the same in adapted form in plastic parts made of nylon, polyacrylate and polyester. Besides these, there are optical brighteners for PS, PE, PP, PVC, ABS, EVA and for coloured coatings. Also here the rule applies: fluorescents can be added to the monomer before polymerisation to form the plastic, or during the extrusion of the polymer to the end product. There are techniques to make sure the brightener will be present primarily at the surface of the plastic article; where it can perform.

Paper
In the paper industry the classical optical brighteners are used to make paper appear as white as possible. In the paper production process much recycled pulp is used, as well as chemicals with a yellow or grey colour. Optical brighteners with
di-, tetra-, penta- and hexa sulphonic cid groups make sure the end product shines white. The more sulphonic acid groups, the better soluble the fluorescent will be in water.

Cosmetics
In eye and face make up fluorescents cover darker shadow surfaces, such as below the eyes, in a safe way.
In colour shampoos for blond and grey hair a special optical brightener not only increases the shine of the hair, but also covers mat and yellowed areas, without making the hair appear darker.