Oil Absorption of Pigment

The Part 5 of ISO 787 gives a method for determining the oil absorption of pigments and extenders." A refined linseed oil is dispersed in small portions if om a burette and mixed with powder using palette knife until smooth consistency is obtained. Different amounts of powder are taken depending on the expected oil absorption. Oil absorption is expressed as a percent of the mass of powder."... 

ASTM D281-95, Standard Test Method for Oil Absorption of Pigments by Spatula Rub-out, 2002. 

Oil Absorption of Pigments Hiding Power Fastness to Light Scale for Pigments Hiding Power Scale for Pigments... 

Absorption, oil n. Oil absorption of a pigment or extender is recorded as the amount of vegetable drying oil required to convert a given mass or volume of the dry powder to a very stiff putty-like paste, which does not break or separate. It is more usually expressed as the pounds of refined linseed oil required for 100 pounds of pigment or gTOOg. 

Table 6-8 Specific surface areas and oil absorptions of some DR pigments.

Iron oxide yellows can also be produced by the direct hydrolysis of various ferric solutions with alkahes such as NaOH, Ca(OH)2, and NH. To make this process economical, ferric solutions are prepared by the oxidation of ferrous salts, eg, ferrous chloride and sulfate, that are available as waste from metallurgical operations. The produced precipitate is washed, separated by sedimentation, and dried at about 120°C. Pigments prepared by this method have lower coverage, and because of their high surface area have a high oil absorption. 

Testing. Various test methods are provided by ASTM (16). These iaclude pigment tests of importance such as chemical analysis, presence of oversize particles, oil absorption, particle size distribution, degree of dispersion, presence of soluble components, etc. Numerous tests are also given by ASTM for the properties of filled and unfilled polymers. These iaclude, for example, such properties as impact resistance, stiffness, viscosity, tear resistance, hardness, color, and electrical resistivity. 

White pigments such as calcium carbonate, aluminum hydroxide, silica, kaolin, or urea-formaldehyde resin are used as filler. The filler functions as an absorbent of melted components to prevent their adhesion on the thermal head. Thus, the filler is required to be high in oil absorption and not to wear the thermal head. 

It seems reasonable to conclude that experimentally determined specific surface areas can only qualitatively relate to the physical characteristics of organic pigments. Instead, their value emerges in combination with other physical or physico-chemical parameters or in the context of application properties such as oil absorption [16] or wettability (Sec. 1.6.5). 

DIN 53199 Bestimmung der Olzahl (Spatelverfahren). ISO 787 T5 General methods of testing for pigments and extenders, Part 5 Determination of oil absorption value. 

Oil Absorption. The oil absorption gives the mass or volume of linseed oil required to form a coherent putty-like mass with 100 g pigment under specified conditions. The mixture should just not smear on a glass plate. For standards, see Table 1 ( Oil absorption ). Materials and apparatus rough glass plate, spatula with steel blade, raw linseed oil. 

Methods based on the experimental production of the dense pigment packing typical of CPVC, e.g., by means of oil absorption, filtration, vacuum filtration, or by measuring the volume of the supercritical film... 

Apart from the morphological and magnetic properties, usual pigment properties such as pH value, tap density, soluble salt content, oil absorption, dispersibility, and chemical stability are of great importance for the manufacture of magnetic recording materials. 

Pigments ideally should be non-soluble solids with low oil absorption to facilitate dispersion and allow maximum pigment loading, which would also reduce the VOC content of the paint. In addition, pigments should be chemically inert, thermally stable, pure in their composition, and nontoxic. 

The term carbon black describes a group of industrial carbons created through the partial combustion or the thermal decomposition of hydrocarbons. Carbon black is unique in that it possesses the smallest particle size and highest oil absorption among the commercially available pigments for plastics. These characteristics help explain carbon black s excellent color strength, cost-effectiveness, and ultraviolet (UV) performance and place it as the most widely used black pigment for thermoplastic applications. 

---