Phenolic pigments stability

Because of the high melt viscosity of polyolefins, normal spinning melt temperatures are 240—310°C, which is 80—150°C above the crystalline melting point. Because of the high melt temperatures used for polyolefin fiber spinning, thermal stabilizers such as substituted hindered phenols are added. In the presence of pigments, the melt temperature must be carefully controlled to prevent color degradation and to obtain uniform color dispersion. 

During fermentation, the betacyanins turned out to be more stable than the betaxanthins, which is assumed to be due to their thermal stability rather than different tendencies of pigments toward microbial degradation. Besides these biological tools, beet extracts may also be purified by column chromatographic techniques. After removal of sugars, salts, and phenolics, the nature-derived color preparation will, however, require E number labeling. ... 

As a beginning toward understanding and preventing this phenomenon, the effect of selected amines and phenol stabilizers on the pigment-sensitized photooxidation of the leuco triphenylmethane dye I to the blue dye II was determined (Scheme 2). 

By far the most important phenolic resins are those made from phenol and formaldehyde. They exhibit high hardness, good electrical and mechanical properties, and chemical stability. Very often they are used in combination with (reactive) fillers like sawdust, chalk, pigments etc. 

Relatively high concentration levels of UV absorbers, 0.25-0.5 %, are used in plastics containing conventional basic stabilization (i.e. a combination of a phenolic antioxidant, organic phosphite and calcium stearate) (Gugumus, 1990). Combinations of UV absorbers with HAS are beneficial in pigmented polyolefins. 

Surfactants— This group includes various bases used for different applications, such as protein dispersants, stabilizers of aqueous pigments, blood preservatives, flotation collectors, etc. Apart from rare cases, they are phenolic derivatives ... 

TABLE 17.11 Influence the Combination of a Phenolic Antioxidant, a Phosphite, a UVA and a HALS on the UV Stability (Time Until a Color Change AE 10 in a Weather-Ometer (Black Standard Temperature 80° C, Intensity 0.55 W/m2 (at 340 nm), and 18 min Rain/2 h) of Gray-Pigmented PA6)... 

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