Plasticised PVC is today’s most widely used electrical insulation material, not only for protecting wires in thousands of everyday machines and appliances but also as the preferred insulation and sheathing for data transmission cables and fibre optics.
In Europe, about 25% of all flexible PVC is used in the production of wire and cables for the electrical industries. Its popularity and widespread use are mainly due to its long-lasting and durable qualities, making all these end-products able to withstand a wide range of operating conditions at exceptionally competitive costs.
PVC's ability to bend and twist without cracking, thus releasing any physical stress, is a safety feature which makes it particularly suitable for an ample range of applications. The addition of plasticisers provides the required flexibility to insulate and sheath metal wires.
By varying the kind and quantity of the plasticisers employed with PVC, cable manufacturers are able to produce a wide range of sheathing strengths and thicknesses. The exact degree of flexibility can be altered to meet the mechanical and ageing requirements of the end-application. Road vehicles, for example, need very different wiring to household appliances.
Furthermore, the overall costs of the finished product can be kept relatively low because the equipment used by wire and cable producers for extruding PVC, although sophisticated, does not require high levels of investment.
It is precisely for their low cost, high permanence and versatility that high phthalates such as DINP, DIDP or DPHP are widely used as general purpose plasticisers. These high phthalates are efficient processing aids, improving PVC melt viscosity and increasing production speeds, resulting in better workability and less out-of-service equipment breakage.
General purpose high phthalates are vital for energy cables used in buildings and for power distribution wiring buried underground which must remain flexible even at low temperatures.
For more stringent cable operating conditions, such as, oil extraction resistance, high temperature resistance or fire resistance, general purpose high phthalates can be blended with or replaced by specialty plasticisers such as tri-isodecyl phthalates, trimellitates, phosphates or polmeric plasticizers.
Tri-isodecyl phthalates, linear undecyl phthalates or trimellitate plasticisers have become the first choice for very high-temperature resistant applications such as the wiring used in close proximity to vehicle engines.
Phosphate ester plasticisers are commonly used in applications where additional flame-retardant and smoke-suppressant properties are important.
Polymeric plasticisers are ideal for use in cables where oil resistance is necessary or when plastic materials other than PVC are susceptible to stress cracking when in contact with flexible PVC cables.
Metals like copper or aluminium account for over 50% of a cable value. With copper prices so high, all flexible PVC cables are recycled in plants specialised in electrical cable recycling. One good example is the SOLVIN Ferrara PVC recycling plant project which is a pioneering recycling operation based in Ferrara in northern Italy. The plant is designed to recycle PVC from cable insulation and other scrap materials. Nowadays many similar initiatives have materialised. Go to www.vinylplus.eu/ for additional information.
Some images reproduced with the kind permission of European Council of Vinyl Manufacturers