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PVC WIRES AND CABLES: BRINGING ESSENTIAL BENEFITS TO SOCIETY

Without wires and cables, our society, as we know it, would not exist. Electricity, electronics, transports, IT, home automation depend on cables, especially in our interconnected and digitalised society. Wires and cables are widely used to power countless appliances and electrical equipment. They are the largest application sector for flexible PVC in Europe, absorbing 7% of PVC resins production.

PVC wires and cables account for around 46% of the European cables market. PVC is used for the production of electric and data transmission cables as well as insulation and sheathing in various fields: classic electric cables for power transmission at low and medium voltage for homes and offices; telephone cables; coaxial cable TV/computer/hi-fi; cables for cars; battery cables and robotics; data transmission cables, LAN and IT.

PVC has in fact several intrinsic characteristics which make it the ideal choice for a range of different applications. For example, PVC is fire retardant and can reduce or suppress combustion in case of fires, preventing flames spreading.

PVC provides insulation, strength and protection at a wide range of operating temperatures: it maintains high thermal stability and resistance to degradation at operating temperatures from 70 °C up to 125 °C and retains its flexibility over very long life-span, at high and low temperatures, including in cold environment well below -30 °C.

Furthermore, PVC wires and cables can last up to 80 years under normal conditions of use. Flexible PVC is a sensible choice for cables and wires because it is affordable, durable, a good insulator and it can be recycled. In 2017, 126,000 tonnes of PVC cables were recycled within the framework of VinylPlus® – the European PVC industry’s sustainability programme (www.vinylplus.eu), representing 20% of the total recycled volumes. Plasticisers make PVC soft and bendable, essential characteristics to produce wires and cables and to ensure durable performance for decades.

The use of plasticiser, as for any other chemical substance, is regulated in Europe by the REACH Regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals) supporting their safe use in many flexible PVC applications with no risk to consumers’ health or to the environment.

Formulations for PVC cables can be defined and optimised choosing among a number of different families of plasticisers. The selection of the right plasticiser is determined by the performance specification of insulation and jacketing (cable performance) and with respect to the process requirement in dry blending and extrusion.

For example:

  • High-temperature specification requires thermally stable and permanent plasticisers;
  • Low-temperature specification requires plasticisers with high flexibility even at the lowest temperature;
  • Resistance to hydrocarbons require high molecular weight or polymeric plasticisers.

The following table summarises the correspondence between cable requirements and plasticiser characteristics.

Cable requirements

Plasticiser characteristic

Good compatibility with PVC 

Similar polarity like PVC

 Good stability

Thermal (oxidative) stability & resistant to hydrolyses

High permanency

High molecular mass
• low-vapor pressure, low volatility
• low migration, high resistance to extraction

Low-temperature flexibility 

In general, a high degree of linearity

Cost effectiveness 

• Good efficiency
• Good processing; high extrusion throughput

Safety 

• Retained flexibility over time-permanency
• Regulatory compliance

The choice of plasticiser also depends on the maximum operating temperature for the cable type.

This operating temperature defines the ageing conditions (ageing temperature and duration), where operating temperature is different from ageing temperature.

European cable producers can choose from a range of plasticisers available on the market; the main plasticisers used in wire and cable applications in Europe are:

  • High ortho-phthalates, such as DINP, DIDP, DPHP, DTDP (C11-C14, C13 rich) and linear phthalates (C9-C11, DUP i.e. Linear C11)
  • Trimellitates, such as TOTM and Linear trimellitates (C8-C10).

Other plasticisers can also be used to address specific technical requirements:

  • Aliphatics, such as adipates or azelates • Polymerics (mainly polyadipates)
  • Phosphates, such as alkyl aryl and triaryl phosphates
  • Terephthalates, such as DEHTP (or DOTP)
  • Valerates, such as PETV (pentaerythritol tetravalerate)
  • Cyclohexanoates.

The PVC value chain is engaged in the research and development of new formulations to ensure maximum safety and protection of the environment and of the health of users and consumers.

VinylPlus® commitment on the sustainable use of additives, for example, resulted in the replacement of lead-based stabilisers in PVC applications in the EU-28 by the end of 2015, whilst European plasticiser producers (www.plasticisers.org) are committed to science and research to offer substances meeting the highest performance and the strictest regulatory standards, adapted to the evolving market demand.

New formulations for PVC cables are currently under development to further improve their performance in fires.

PVC WIRES AND CABLES – PROPERTIES

  • High insulation characteristics
  • High versatility in terms of formulations
  • High thermal stability/resistance to degradation at operating temperatures from 70 °C up to 125 °C
  • Flexibility over very long life-spans, at high and low temperatures well below -30 °C
  • High productivity and energy efficiency during cable manufacture at relatively low cost
  • Resistance to hydrocarbons
  • Flame retardancy and fire ignition and propagation prevention
  • Recyclability