Have you ever looked up at the sky and asked yourself, “Why is that blue”? (It is complicated, but blue light scatters more than the other wavelengths and thus is more visible. For more information see Rayleigh scattering.) I have asked myself similar questions. Questions that consistently come up in the rubber industry are: Why is neoprene black? Why is fluorosilicone blue? Why is silicone a bright red?
As problem solvers here at NEDC, we have the answer to all of those questions.
The most popular rubbers are nitrile, neoprene, SBR, fluoroelastomer, and butyl rubber. The majority of rubbers are black, originating from something called the filler in the rubber compound. The filler typically used is called “carbon black,” which is dispersed throughout the elastomers and ends up producing a black color. Carbon blacks do not just provide color, but they generally provide an increase in mechanical properties such as tear, hardness, tensile, and abrasion. An example of an elastomer that typically does not contain carbon black is silicone.
Silicone has a bright red color that is quite unique; this color comes from the red iron oxide in the rubber compound. The iron oxide contributes to silicone’s excellent heat resistance and is typically considered an additive as opposed to a filler. Silicone’s heat resistance can exceed 600°F if compounded correctly. When it is said the silicones color is “natural” they are referring to red; even upon curing the silicone, the red color is maintained. While silicone is most often provided in red, it is also provided in a variety of colors, such as translucent, white, blue, and black. However, it would be wise to be cautious when a silicone is blue because it may be fluorosilicone.
Fluorosilicone is usually identified by its notable bright blue color. You would assume that fluorosilicone is typically blue without additives, but on the contrary, this blue is created on purpose. The fluorosilicone is typically dyed blue for identification purposes to differentiate fluorosilicone from other elastomers. Fluorosilicone without the blue additive is a beige color, but blue is preferred and sometimes required by some fluorosilicone specifications (such as AMS-R-25988, and AMS 3329). Fluorosilicone exhibits great resistance to oil and other hydrocarbons; a polymer that does not offer this great resistance is natural rubber.
All of this started back in 1839 when Charles Goodyear first discovered vulcanization on that potbellied stove. Natural rubber has a naturally occurring cream like color, a result of the aggregate of naturally occurring chemicals in the rubber such as: fatty alcohol esters, unsaturated fatty acids, and more.
NEDC provides elastomers ranging the color spectrum. While certain colors are not typically provided, some abnormal colors may be available upon request. If you have an application that requires the rubbers listed above, please contact firstname.lastname@example.org.