A new cable and wire insulation option is giving purchasers greater choice when safety, size, weight and durability are important considerations
While PVC insulation is a mainstay of the wire and cable industry thanks to its mechanical and electrical properties and low cost, it presents environmental issues. PVC is a halogen-containing material hazardous to health and equipment when burned.
Halogens are elements such as fluorine, chlorine, bromine and iodine. Halogens are highly reactive and can be harmful to people and animals. Common cable insulation, such as PVC, contain high amounts of halogens. The C in PVC is chloride, which is an ion of chlorine. PVC contains about 29 per cent chlorine by weight. FEP and PTFE contains about up to 76 per cent fluorine. FEP, when burned, produces toxic acid. Under normal circumstances halogens are stable and present no danger. Problems arise when they burn.
A halogen-containing plastic can release hydrogen chloride, hydrogen fluoride and other dangerous gases when burned. When hydrogen chloride comes in contact with water, it forms hydrochloric acid, which is also dangerous. Beyond being toxic to humans and animals, these gases are also highly corrosive to metal.
Thus, the concern with common wire and cable insulating materials is that they will emit toxic gases, smoke and acids when they burn.
Newer materials, principally low-smoke, zero-halogen (LSZH) plastics, emit no dangerous gases or smokes when burned. They may contain miniscule trace amounts of halogens, well under one per cent, but they essentially are halogen free. The drawback to LSZH is that it cannot be conveniently recycled and reused. Like PVC, it will sit in a landfill for centuries.
Alpha Wires new EcoWire hook-up wires use flexible Noryl insulation to provide an environmentally friendly alternative to PVC. Noryl is a modified polyphenylene ether (mPPE) thermoplastic that is inherently lighter, tougher and more flame resistance than PVC.
As a replacement for PVC, mPPE brings many advantages including:
Environmentally friendly, mPPE contains no halogens, phthalates or heavy metals and meets RoHS and WEEE requirements.
Superior dielectric properties allow a reduced wall thickness while maintaining the same electrical properties as PVC. Diameter of equivalent wires can be 25 per cent smaller. Fig 1 compares an 18 AWG hook-up wire in PVC to the same wire in mPPE. Both wires have the same performance characteristics.
Low specific gravity (1.03) is 25 to 40 per cent lower than other insulation materials, such as PVC, polyethylene, and cross-linked polyethylene. Along with the reduced wall thickness, the low specific gravity yields significant weight savings of around 25 per cent.
Even with the thinner walls, mPPE offers 10-times better abrasion and pinch resistance than PVC.
mPPE offers the same flammability rating as PVC, meeting UL VW-1.
Wires and cable with mPPE insulation meet UL 1581 requirements for operation at 80 and 105oC. With a higher temperature range than PVC, mPPE does not need secondary processing operations as required with cross-linked polyethylene.
Regarding recycling, mPPE is a thermoplastic which is relatively easily recycled because it does not contain hazardous materials.
After the advantages, are there any drawbacks? Naturally,
mPPE-insulated wires and cables are somewhat more expensive than PVC wires, plus they are new. Engineers specifying wire and cable can be risk adverse, selecting the known over the unknown. A cost-benefit analysis including safety, size, weight and durability, may well prove mPPE insulation is the best choice. Such analysis depends on the application.
Adoption of mPPE-based products like Alpha EcoWire hook-up wire should not be hindered by its apparent novelty. Underwriters Laboratories has approved mPPE as a suitable insulation for over fifty AWM cable styles, so it can be confidently applied when a tough, compact and non-halogenated wire or cable is required.
