Carbon black pigments dispersion effects

The use of carbon black pigmentation/stabUization in thermoplastics for external exposure is widely applicable but has to be undertaken with care since it increases radiant heat absorption and hence the possibility of distortion. The type, particle size and degree of dispersion of the carbon are important for optimum efficacy. Additions in the order of 1-3% are generally sufficient for this purpose but in rubbers, where the carbon black also has a reinforcing function, considerably more is used. Other pigments have varying effects, an example being iron oxide which protects polyolefins yet catalyses the decomposition of PVC. 

The aim of this chapter is to provide an understanding of how carbon black particle size and shape translate into dispersion quality and other performance attributes in plastics applications. While this chapter focuses on carbon black s effectiveness as a pigment, some attention will also be paid to some of the other plastics performance properties it influences, such as stability against UV radiation, effects on mechanical properties, and electrical conductivity. At its conclusion, this chapter will help the reader select an appropriate carbon black grade for specific plastics applications. 

In addition to jetness, plastics pigmented with carbon blacks typically exhibit color undertones. Undertone in black plastics appears as a distinct blue or brown-to-orange undertone, depending on the particle size of the carbon black used. In general, in full-shade, black molded applications, fine-particle-size carbon blacks impart a bluer tone. This behavior reverses itself in tints. Large-particle-size carbon blacks impart bluer undertone. Note that the effects of fillers, polymers, and dispersion can alter the typical behavior described above. Tint strength is the relative ability of the carbon black to darken a resin colored with chromatic pigments. 

We consider the case of a black ink for plain paper, to be apphed by TIJ print head. As mentioned before, black pigments are quite effective at achieving high optical density on porous media, so we pursue a carbon black dispersion as the colorant. An investigation of the patent hterature shows that a charge stabilization level of... 

The addition of pigments to polymers is a very effective practical method for increasing the resistance to photodegradation. Carbon black is by far the most effective. It has been used for years as a filler in rubber vulcanites, but in thermoplastic materials such as polyolefins it also has a protective effect against photodegradation. This was shown for the first time in 1950 by Wallder et al. [126] they demonstrated that the weathering properties of polyethylene are improved by the addition of about 2% carbon black. The effect is dependent on the degree of dispersion and on the size of the particles. Channel Black (particle size about 30 nm), for instance, is more efficient than Furnace Black (particle size 80 nm). The role of carbon black is not only to prevent the absorp-... 

Rubber compounds very often contain smaU-particle fillers such as carbon black and silica, to improve processability and physical properties, and to reduce material costs. The most common filler is carbon black, use of which as a pigment dates to ca. 4000 BC. Methods to incorporate fillers, and the effect of their distribution and dispersion on properties, are central considerations, with... 

Carbon black performs the combined antioxidant and light-filtering effect, and its efficiency depends significantly on particle size and on dispersion in the polymer medium. The photo-stabilizing efficiency of other pigments is usually considerably lower. 

Two percent by weight of a well-dispersed carbon black of fine particles in the range 15-40 pm should extend to outdoor life of most low-density polyethylene and all polypropylene grades to as much as 20 years in temperature climates and 76 years in tropical climates. Other pigments will have a much lower protective effect than carbon black. 

Condensed tannins are excellent clay dispersants. Sulfite extracts from conifer tree barks are very effective in reducing the viscosity and increasing the gel strength of muds used in well drilling (72, 92, 145, 246, 248). Condensed tannins still face strong competition from lignosulphonates for this application, particularly because of the comparatively low thermal stability and salt tolerance of the tannin (96). However, reaction of tannins with chromium increases their thermal stability considerably to permit their use in muds for wells drilled as deep as 6000 feet (208). Sulfonated condensed tannin derivatives have found use as dispersants in other specialty applications, such as ceramic clays, pigments, carbon black, and pesticides (93, 96). 

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