Resins carbon black pigment effects

Other spherical fillers include carbon black. This has several roles particularly in combination with elastomers, e.g., black pigment, anti-oxidant and UV stabiliser, reinforcing filler, and an electrical conductor when used at 60% concentration. Wood flour is particularly effective in phenol/formaldehyde and melamine or urea/formaldehyde thermoset resins because the phenolic lignin component in the wood reacts with the methylol groups (-CH2OH) in the growing polymer. 

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. 

The use of the concentrate or masterbatch method has proven to be one of the most effective methods of incorporating carbon black into a resin. A masterbatch, as defined in the plastics industry, is a resin containing a high concentrate (20-50%) of pigment and other fillers that is subsequently reduced in a compound resin to accommodate the end-use requirement. 

Both one-part and two-part neoprene sealants are made most commonly using general purpose neoprenes of the GN and W types. Two-part compositions contain 25-30% neoprene plasticized with materials such as dioctyl sebacate or resinous plasticizers, stabilized with phenolic antioxidants, filled with reinforcing pigments such as carbon black and hard clays, and modified with cure-rate regulators and acid acceptors such as zinc oxide and magnesium oxide. Cure accelerators such as polyamines (i.e., tetraethylene pentamine) are used at 5-10 phr based on neoprene. Heat-reactive phenolic resins are also effective. One such composition is shown in Table 12. 

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