Fade-resistant coloring

This specification covers an oil-base, lead- and chromate-free painting system for new or weathered (white or red rusted) galvanized steel. It is also effective on nongalvanized steel cleaned with hand or power tools. This system is suitable for use on parts or structures exposed in Environmental Zone lA (interior, normally dry) and Zone IB (exterior, normally dry). The finish paint allows for a choice of durable, fade-resistant colors. 

The finish paint allows for a choice of durable, fade-resistant colors. 

Whereas the eadiest fluorescent-dye pigments would last only 20 days outdoors in a screen-ink film, fade resistance has been improved to such an extent that some modem daylight-fluorescent coated panels stiU have useful color after nine months or mote in Florida sunlight in a 45° exposure tack facing south. The fluorescent layer is usually coated with an acrylic film containing a uv absorber. Indoor-accelerated exposure equipment is, of course, invaluable in the development of such systems. Better dyes and resins very likely will make possible fat mote stable coatings in the future. 

Pigments and Extenders. Pigments are selected for use in house paints based on thek appearance and performance quaUties. Appearance includes color and opacifying abiUty. Performance quaUties include ultraviolet light resistance, fade resistance, exterior weatherabiUty, chemical resistance, as well as particle size and shape. Toxicity profiles and safety and health related properties are also important criteria in pigment selection. 

The FS system developed by CIBA Additives seems to be a breakthrough for color-critical PO applications. These new systems do not contain phenolic antioxidants so they provide good color stability and gas fade resistance, long term thermal, and UV light stability. They improve the activity of the HAS. Doverphos HiPure 4, introduced by Dover Chem. Corp, is a high purity processing and heat stabilizer, cost effective, and FDA approved for food contact applications and medical devices. 

Phenol-free process/light-stabilizer, low color, gas fade resistant... 

Dyes, often also called coloring matters or colorants, are intensely colored, soluble organic substances used to impart color to fibrous materials (see Textbox 66). Not all colored and soluble organic substances, however, are dyes only those whose molecules have a considerable structural complexity are useful for imparting color to other materials. Moreover, a substance is considered a dye only if the color it imparts is fairly permanent, that is, resistant to fading and disappearance. 

Clearly, a number of chromogenic systems are available and may be varied between laboratories. The horseradish peroxidase-DAB system is probably the most widely favored as the brown reaction product contrasts well against a wide range of counterstains and mountants. DAB is not only alcohol resistant but can be visualized in the electron microscope. Osmification can produce a more intense dark brown-black color and a similar effect is achieved by post-treatment with nickel sulphate or cobalt chloride but such enhancement is seldom necessary. The reaction product is relatively stable with fading occurring only after years in routine storage. 

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