Some soil types provide the breeding ground for termites. Termites attack telecommunication infrastructures that lead to potential damages to the whole system. Cables that are buried directly in the soil are more exposed to the attack from termites. Therefore, termite-resistant cable sheathing compounds are required to protect fiber optic cables from the attack of termites.
Polyamide-12 (Nylon-12) is one of the most widely used materials to protect products from termite attacks. Alternatively, termite-resistant additives can also be added to the sheathing compounds. Usually, fiber optic cable manufacturers use Polyethylene (HDPE, MDPE, LDPE or LLDPE) or PVC (Polyvinyl Chloride) as the outer sheath material. If a termite-resistant additive is mixed with sheathing compounds, compatibility of both materials shall be tested and verified.
A carrier resin is used in termite-resistant additives that will ensure the compatibility with the main sheathing compound. Some termite-resistant additive suppliers make use of Ethyl Vinyl Acetate (EVA), which has good compatibility with PVC and PE compounds.
Though there are different solutions to achieve termite resistant, use of Bifenthrin as an active ingredient in the additive is common due to safety factors. Bifenthrin is an insecticide in the pyrethroid family. Pyrethroids are manmade versions of pyrethrins, which come from chrysanthemum flowers. Bifenthrin is used on various agricultural crops and in homes. Bifenthrin was first registered for use by the United States Environmental Protection Agency (U.S. EPA).
The specific gravity of the termite-resistant additive containing Bifenthrin may range from 0.9 to 1.1 g/cubic cm. It is free from Pb (lead) and has good heat resistant properties. The chemical formula is C23H22ClF3O2.
Exposure to high doses of Bifenthrin should be avoided. Tests conducted have proven that lower doses are safer to handle. Water solubility is less than one part per billion. Since the chemical is not soluble in water, it does not pose any threat to the soil where the cables would be deployed.
In order to provide sufficient termite-resistant properties to the outer sheaths, a recommended ratio of sheathing compound to additive is 98:2, which is equivalent to 2% additive.