Standards for pigments

There are as yet no national or international (ISO) standards for mixed metal oxide pigments, and none are expected in the foreseeable future. However, the general tests of chemical, physical, and optical properties described in ASTM, DIN, or ISO standards for pigments may be utilized, such as DIN 6174, DIN 55 986, and ISO 787 Part 16 for the optical properties, and ISO 787 Parts 1-20 for the physical properties (see also Table 1). 

Table 13.1 ASTM Standards for Pigment Specification Designation Title...

Color pigments are often mixed in adhesives. Since there are many types of pigments, which can affect the performance of adhesives, thorough discussion between users and suppliers of pigments is indispensable. Standards for pigments are shown inO Table 40.3. 

An important property of a pigment is its ability to maintain its color when exposed to light, weather, heat, and chemicals. This property is seldom measured for pigments alone. Rather it is determined for the dispersion of a pigment in a desired medium, eg, paints or plastics, and in many cases it is compared to the performance of a standard pigment. The observed changes are the result of complex pigment and media reactions and their possible interactions. In aH evaluations, time of exposure plays a role. 

Whiteness and Brightness. Photometric instmments, originally developed by the paper industry, are used for these measurements. Values are compared against standard white pigments such as BaSO, Ti02, or MgO. 

Acceptance of a color recommendation made by the coatings suppHer effectively eliminates the time and cost involved in an initial color match and ensures selection of a pigment combination appropriate to the coating use. If, however, a coatings user provides a sample or standard for a color match, formulators need the foUowing information. 

There are commonly accepted experimental standards for the determination of conductivity and specific resistance in aqueous pigment extracts [18]. The electrical conductivity y is calculated from the electrical conductance its inverse is the specific resistance f=l/-y, derived from the electrical resistance. Additional experimental methods have been developed for the determination of soluble sulfates, chlorides, and nitrates [19]. 

A number of thermal stability tests arc available, some of which have developed into national (DIN) or international industrial standards (ISO). Pigments in thermoplastic systems, for instance, are studied under heat extrusion conditions [110]. The colorant to be tested, possibly together with titanium dioxide, is dispersed in the thermoplastic, using a mixer and a granulating extruder (Sec. 1.8.3). The pigmented test pellets are then fed into a screw extruder which ejects a standardized test specimen with defined dimensions [111]. Starting at the lowest possible temperature level, the extrusion temperature is increased by intervals of 10 or 20°C between samples. 

In white reductions, P.R.208/polyolefin systems only withstand temperatures below 200°C, while transparent specimens (0.1%) are stable up to approximately 240°C. Thus the pigment is a suitable and economical candidate for polypropylene spin dyeing, provided the temperature is kept below 200°C. It is also possible to apply higher temperatures if a color shift towards more yellowish shades is acceptable. In terms of lightfastness, P.R.208 meets the common standards for interior application. 

Special distribution functions are specified in some standards (e.g., power distribution, logarithmic normal distribution, and RRSB distribution). Methods of determination for pigments are rated in Section 1.2.2. 

Anticorrosive chromate pigments are summarized in Table 45. Their possible combinations with various binders are listed in Table 39. Standards for specifications of chromate pigments are listed in Table 1. 

Quality standards for some flavor constituents will eventually be developed—linalool for muscats, for example, and perhaps phenethanol for certain types of wine. Kahn and Conner (124) have published a rapid GLC method for phenethanol. It has been suggested (60) that detection of bacterial activity from the presence and amount of minor bacterial byproducts (arabitol, erythritol, and mannitol) may be useful. Based on GLC determination of carbonyls, esters, and higher alcohols, beers were accurately classified into three categories (125). Anthocyanin content has been determined quantitatively by using molar absorbance values for five anthocyanin pigments (126). 

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