Polychlorinated naphthalene

Polychlorinated naphthalene (PCN) products are made by chemically reacting chlorine with naphthalene, a soft, pungent solid made from coal or petroleum and often used for mothproofing. The generic chemical formula is C₁₀H_10-nCl_n. Commercial PCNs are mixtures of up to 75 chlorinated naphthalene congeners plus byproducts and are often described by the total fraction of chlorine. As the chlorine proportion grows, PCNs become increasingly waxy or firm solids at room temperature. Some PCNs make effective insulating coatings for electrical wires. Others have been used as wood preservatives, as rubber and plastic additives, for capacitor dielectrics and in lubricants.

PCNs started to be produced for high-volume uses around 1910 in both Europe and the United States. In Europe the largest volume products were called Nibren waxes, made in Germany by Bayer. Other European PCN tradenames included Seekay (UK, from ICI), Clonacire (France), Cerifal (Italy) and Woskol (Poland). In the United States, the largest volume PCN products were called Halowax, from a New York company of the same name that was later owned by Union......
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