Dispersions discoloration

Leaching in aqueous environment Must be well dispersed Discoloration... 

Polymer-bound antioxidants must be molecularly dispersed (i.e. infinitely soluble) and cannot be physically lost from the substrate. High-MW phenolic AOs are preferred for applications requiring FDA approval, minimal discoloration, and long service life at high temperatures. Antioxidants are used for protection of polymers, plastics, elastomers, foods, fuels and lubricants. 

In terms of weatherabilityf polystyrene does not exhibit ultraviolet stability and is not considered we ather-re sis tan t as a clear material. Continuous, long-term exposure results in discoloration and reduction of strength. Improvement in weatherability can be obtained by the addition of ultraviolet absorbers, or by incorporating pigments. The best pigmenting results are obtained with finely dispersed carbon black. 

The discoloring is likely to be caused by the photoreduction of silver chloride and/or silver phosphate in the skin. X-ray dispersive analysis of skin and other tissues reveals that the granules consist of silver complexed with sulfur and/or selenium. The photoreduced deposits are not removed by the body, and there are no clinical means of removing them. 

Riedel and Leopold [35] investigated the degradation of omeprazole in organic polymer solutions and aqueous dispersions of enteric-coating polymers by UV spectroscopy. Data were compared with those obtained in a previous high-performance liquid chromatographic (HPLC) study. For comparative purposes the cationic Eudragit RS 100 and the monomeric acid acetic acid were included in this study. The discolorations of... 

The colloidal dispersion resulting from thermal/chemical oxidative conversion can rapidly retrograde, which makes immediate neutralization of the acid product to a pH 8.0 to 8.5 mandatory. Discoloration of the paste is lessened when sodium bisulfite is added to the starch slurry and/or sodium sulfite added to the paste. Multivalent ions in the paste can induce colloidal destabilization, and may require the addition of a sequestrant."... 

SOFTENER GS-25 may be used as a general purpose textile softener to impart a soft, full hand with minimal effect on the shade of dyed fibers or optical brighteners and on the discoloration of whites. It is a thin, pourable liquid for easy handling from either bulk or drums. It is readily dispersible in water at any temperature from cold to hot. 

A wide variety of synthetic polymer resins can be used as water repeUents for concrete. These include acrylates, epoxies, chlorinated mbber, polyvinylbutyral, urethanes, elastomeric sUicones, and fluoropolymers. They are generaUy appUed from organic solvents or, in some cases, aqueous dispersions or latexes. Some have the disadvantage of inducing gloss and discoloration in the treated masonry. 

Carbomers are discolored by resorcinol and are incompatible with phenol, cationic polymers, strong acids, and high levels of electrolytes. Certain antimicrobial adjuvants should also be avoided or used at low levels, see Section 11. Trace levels of iron and other transition metals can catalytically degrade carbomer dispersions. Intense heat may be generated if a carbomer is in contact with a strong basic material such as ammonia, potassium or sodium hydroxide, or strongly basic amines. 

U.S. Pat. No. 6,743,507 (June 1, 2004). F. Barlow, Y. Khanna, D.B. Pietsch, and J. Underwood. Cellulose fiber reinforced composites having reduced discoloration and improved dispersion and associated methods of manufacture. 

Braid surfaces at the failure point and a spot away from that area were analyzed. The external and internal surfaces of the braid at the failure area were mildly discolored because of oxidization, similar to the effect of overheating a metallic object. Optical microscopy and scanning electron microscopy showed no disturbance to the weave pattern, no deformation of metal wires, and no surface defects, based on the comparison of defective and normal areas. Energy dispersive x-ray (EDX) showed similar concentrations of iron (Fe), nickel (Ni), chromium (Cr), and molybdenum (Mo) in both areas, indicating stainless steel. A small amount of silicon (Si) was detected that was attributable to environmental contamination such as dust and dirt. 

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