Electrical cable covering
Flexible PVC around a metal conductor.
Material
PVC insulation or sheath: PVC
Material selection rationale
- Electrical insulation
- Separates conductors from each other or from contact.
- Flexibility
- Allows a formulated cable covering to bend with the cable.
- Flexible insulation geometry
- A continuous covering must bend with the conductor without exposing it; an electrically insulating polymer still needs controlled thickness and formulation.
How it becomes a product
- Formulate for flexibility: PVC is mixed with plasticisers, stabilisers and other additives selected for the cable.
- Extrude around the core: The compound is extruded around a conductor or cable core and cooled as a continuous covering. The compound is cooled around the moving conductor, with the specified thickness and continuity checked for the finished cable.
Preparation routes
Vinyl chloride route
Free-radical addition polymerisation. Vinyl chloride molecules link into PVC chains. The resin is then formulated differently for rigid pipes and flexible coverings. The original double bond is consumed, while the C–Cl bonds remain in the repeat unit. Flexible and rigid PVC can therefore have the same polymer origin.
An initiator starts chain growth. Stabilising additives and, for flexible formulations, plasticisers are separate from the monomer. Plasticiser acts mainly by altering chain mobility; it is not a second polymerising feedstock.
- PVC: monomer production, polymerisation and usesChemical Industry Education Centre, University of York
From ethene to vinyl chloride
- Ethene + Chlorine → 1,2-Dichloroethane
Direct chlorination adds chlorine across ethene's double bond.
- 1,2-Dichloroethane → Chloroethene
Industrial cracking removes hydrogen chloride, leaving the double bond in vinyl chloride.
- PVC: monomer production, polymerisation and usesChemical Industry Education Centre, University of York
Sources
- PVC: monomer production, polymerisation and usesChemical Industry Education Centre, University of York