Light fastness determination

Standards exist for determining the light fastness of colored pigmented plastics in daylight and in xenon arc light, i.e. in accelerated exposure equipment, and for determining the weathering fastness. 

Liu CZ, Zhou HY, Zhao Y. (2007) An effective method for fast determination of artemisinin in Artemisia annua L. by high performance liquid chromatography with evaporative light scattering detection. Anal Chim Acta 581 298-302. 

Light fastness is mainly determined by the nature of polymer and dyestuff and by the interaction between the two. Additives like pigments and stabilisers (antioxidants) are important. The better the light fastness of the polymer, the greater the chance that it will have a good colour fastness. 

An interesting approach is a method that uses the modulation of the degree of circular polarization (e.g., between pure 1-cpl and linearly polarized light) to determine fast isomerization kinetics [71]. However, preliminary results on [Co(ox)(phen)2] and rhodamin 6G 14 were not followed by the announced full papers, and the arcticle is rarely cited. In principle the concept may be used to determine interconversion and the CD spectra of rotamers (like 14) which are the reactants in asymmetric synthesis (see Sec. II.C.). 

A simple and usable method has thus been found for determining the light fastness of dyed materials. There was still a need for a standard method for the evaluation of dyes. As is well known, a dye fades more rapidly in light tints than in the deeper tints, and different fastness ratings are obtained for one and the same dye depending on the depth of tint. 

The book is intended principally to introduce to the beginner the mediods of dye chemistry, and not merely to present a collection of recipes. To this end, the chapter on the practical work in the organic industrial laboratory has been reworked and enlarged in order to clarify all the important points. The chapter on analysis of dyes has been revised so that the student may gain some insight into this difficult field. Also, the section on the determination of light fastness has been rewritten, and we are grateful to Dr. Ris (Basel) for his contributions to this subject. These additions have increased the scope of the book. We hope that they have also increased its usefulness. 

The introduction of these standards simplified matters a great deal. By their use, it became possible to compare dyes of any depth or tint and, of special importance, on all the various fibers. Thus, this set of blue standards has become an absolute standard for the determination of light fastness and it has become possible to assign a numerical value for light fastness to every dye used in practice. 

The following factors, in combination with the plastic to be colored, are decisive in determining the suitability of a colorant for a particular application namre, thermal load capacity (level and duration), light fastness, weather resistance, migration tendency (solvent and cmitact bleeding, blooming), plateout (deposits on metal surfaces in contact with melt) and influence on flow behavior [45]. 

Light fastness can be determined by the following test norms ... 

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