Q: I am trying to ascertain whether polyvinyl chloride (pvc) or other halogen-containing insulation is in any real danger of getting superseded in the foreseeable future by non-halogen types in the United States for wire and cable insulation applications. Any comments on this?
Prof. Edward D. Weil
A: Tests comparing pvc and zero-halogen conductors indicate that zero-halogen-insulated conductors have a delayed ignition, emit less dense smoke and less total smoke, are six times less corrosive than pvc conductors, are three times less toxic than pvc conductors, and have significantly lower carbon monoxide emission levels. However, without a regulatory mandate, I do not personally see low-smoke/zero-halogen cables gaining a foothold in the telecommunications-cable market in the United States. Why? Increased cost to the end-user.
I recently spoke with several manufacturers of telecommunications cable regarding what percentage of their total production and domestic sales were zero-halogen. Less than 1% was the answer I received.
Halogens found in insulating materials include chlorine, bromine, and fluorine. The most common halogenated insulating material is polyvinyl chloride (pvc). Plasticized pvc compounds have been used for decades for insulation and jackets for building cables.
While halogens improve certain properties?flame, chemical and oil resistance?they also have some negative effects. During combustion of halogenated insulating materials, the gases produced react with moisture to form halogen acids. These acids?for example, hydrogen chloride and hydrogen bromide?create corrosion, smoke obscuration, and toxicity.
Donna Ballast is a communications analyst at the University of Texas
at Austin and a bicsi registered communications distribution designer (rcdd). Questions can be sent to her at Cabling Installation & Maintenance or at PO Drawer 7580, University of Texas, Austin, TX 78713; tel: (512) 471-0112, fax: (512) 471-8883, e-mail: email@example.com.