Carbon Black Testing for Cables

Cables used for outdoor applications will be subject to higher levels of UV radiation than those used indoors unless specifically protected from it. The effect of prolonged exposure of plastic materials to UV radiation sees a degradation of the molecular structure of the polymer, causing premature ageing and embrittlement.

One means of protecting the polymer from these issues is by the addition of special UV absorbers, the most common of which is carbon black content. Carbon black absorbs the UV rays and transforms them into less harmful thermal energy. Typically, an addition of 2% carbon black will offer a reasonable degree of UV resistance. As a result, carbon black testing (or UV resistance testing as it is also known as) is useful in determining the likely UV resistance of a material.

UV resistance testing can be assessed by thermographic analysis. The test methodology for this carbon black testing sees the samples heated from 30^oC to 700^oC at a rate of 10^oC per minute, under a nitrogen flow to determine the carbon content in the materials. The nitrogen flow prevents any oxidisation of the carbon black so that the residual mass remaining at the end of the test procedure is equivalent to the carbon black content in the material. TGA thermographs are used to record the process.