Lightfastness and weatherfastness

High-grade pigments cannot be studied both in solution and in the solid state, because they are insoluble in almost all solvents. 

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Only a few azo metal complexes are available as pigments. Most of these are very lightfast and weatherfast. The chelating metal is usually nickel, and less commonly, cobalt or iron(II). 

Flavanthrone Yellow, the only commercially used flavanthrone, is a moderately brilliant reddish yellow. Excellent lightfastness and weatherfastness, combined with good solvent and migration resistance, make this pigment an attractive supplement to Anthrapyrimidine Yellow, mainly in the automotive finish industry. 

Lightfastness and weatherfastness of quinacridone pigments (Sec. 3.2) deteriorate in the order 2,9 - 3,10 - 4,11 substitution. It is assumed that decreasing the distance between substituents and NH function disturbs the formation of hydrogen bonds [14] a tendency which culminates in the very poor light and weather resistance of 5,12-N,N -dimethyl quinacridone. 

Metal complex formation considerably improves both lightfastness and weatherfastness in o,o -dihydroxyazo and o,o -dihydroxy azomethine pigments, usually compromised by distinctly dull color. 

There is no precise definition for the frequently used term application fastness of a pigment. It usually refers to the behavior exhibited by a finished product used in accordance with the specifications. The term may thus refer to a print, a coated object, or a plastic product, and the list of features ranges from properties such as lightfastness and weatherfastness to migration fastness and fastness to solvents. In this context, there is a certain amount of emphasis on features which play a role in connection with packaging materials and packed articles. 

Lightfastness and weatherfastness of a pigmented system improve with the depth of shade i.e., the system becomes more stable as the pigment concentration in-... 

Since lightfastness and weatherfastness are properties of entire pigment-vehicle systems, additional components must be expected to have a more or less pronounced effect on the sensitivity of a material. In referring to test results, it is therefore necessary to mention the exact composition of the sample. In some systems, problems arise with peroxides, which may rapidly destroy organic pigments. UV absorbers, on the other hand, may improve the lightfastness of a system. 

Azo pigments have become considerably more important in recent years as new products have been developed to meet increasingly stringent industrial requirements. Their properties in application, including lightfastness and weatherfastness, resistance to solvents, migration, and heat has improved appreciably. The proliferation of azo compounds has raised the fastness standards of azo pigments to a previously unknown level. 

Finishing not only improves the application properties of a pigment, such as hue, tinctorial strength, brilliance, transparency/hiding power, dispersibility, and flow behavior, but also considerably enhances its lightfastness and weatherfastness and its solvent and migration resistance. 

Full shades of Toluidine Red are extremely lightfast and weatherfast, but deteriorate rapidly as the pigment is reduced with white pigment. In full shades, the lightfastness equals step 7 on the Blue Scale, while 1 4 Ti02 reductions only reach step 4. The pigment is therefore used preferably in full or similarly deep shades. Recommendations include emulsion paints for interior application or short-term advertisement and marking purposes. 

Very lightfast red shades can be produced by combining P.R.14 with Molybdate Red. P.R.112 is a member of the same class of pigments, behaves similarly, and is particularly suitable as a partner for P.R.14 in blends which approach the colors of Toludine Red (P.R.3) but provide much improved lightfastness and weatherfastness. 

In full shade and in similarly deep shades, P.R.253 shows good lightfastness and weatherfastness with some darkening. White reductions with TiOz, however, exhibit noticeably less weatherfastness. 

P.Y.154, which was introduced in the mid-seventies, affords a somewhat greenish yellow shade of very high lightfastness and weatherfastness. Its shade is distinctly redder than that of P.Y.175 and noticeably redder than that of P.Y.151, both of which are also members of the benzimidazolone series. P.Y.154 is completely or at least almost completely resistant to the major organic solvents. The list includes alcohols, esters, such as butylacetate, aliphatic and aromatic hydrocarbons, such as mineral spirits or xylene, and dibutyl phthalate. 

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