Material · Engineered · C2H3Cl

Polyvinyl chloride

The polymer that is over half chlorine by weight — cheap, rigid or flexible on demand, and the reason chlor-alkali plants run at the scale they do.

Construction material Insulator

Polyvinyl chloride is unusual among plastics in being mostly not oil. Chlorine accounts for more than half its weight, and that chlorine comes from salt, so PVC is the polymer least exposed to the price of petroleum and the one that gives chlor-alkali electrolysis its reason to run at scale.

Its other distinction is range. The same polymer is rigid pipe and soft flooring depending on how much plasticiser is added, which is why one material appears in so many unrelated products — and why the additives, rather than the polymer, are usually what is being argued about.

Uses

Construction takes most of it: pressure and drainage pipe, window and door frames, cladding, flooring, and the insulation and sheathing on low-voltage cable. Rigid PVC does not rust, does not rot, and does not need painting, which is the whole argument for it underground.

Flexible PVC, plasticised, becomes hose, sheeting, artificial leather and the tubing used throughout medicine — where its clarity, flexibility and low cost matter more than its longevity.

Environmental impact

PVC is the most contested of the common plastics, on three separate grounds. Its plasticisers can migrate out of the product; some of its historic stabilisers were lead or cadmium compounds; and burning it uncontrolled produces hydrogen chloride and, at the wrong temperatures, dioxins.

Each has been addressed rather than settled — tin and calcium stabilisers replaced the heavy metals, and controlled incineration scrubs the chlorine — and PVC's durability in the ground remains simultaneously its main advantage in a pipe and its main objection in a landfill.

Medium confidence Weak evidence

How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.

How this connects

Where a connection has been confirmed by an outside reference, that reference is named beside it.

contains

Chlorine — element · more than half the polymer's weight, and the reason PVC is the plastic least exposed to the oil price
Carbon — element
Hydrogen — element

is sourced from

Chlorine — element · the chlorine arriving from chlor-alkali electrolysis of salt
Ethylene — compound · via ethylene dichloride and vinyl chloride — the chlorine comes from the chlor-alkali industry, and PVC is where about a third of world chlorine production ends up

is used in

Construction — industry · pipe, window frames, cladding and cable, which is where most of it goes

is an alternative to

Copper — element · in plumbing: PVC displaced copper for drainage and much of supply on cost and on not corroding, at the price of a lower temperature limit and a material nobody wants to burn
Polyethylene — material · in pipe and packaging: polyethylene is tougher and easier to weld and contains no chlorine, where PVC is stiffer and cheaper per unit of pressure rating
Leather — material · as synthetic leather, which is mostly PVC or polyurethane over a fabric backing — cheaper, uniform, and it does not develop a patina because there is no collagen to age

is produced by

Polymerisation — process · from vinyl chloride, itself made from the chlorine of chlor-alkali electrolysis

is an input to

Extrusion — process · pipe and window profile, which is most of what PVC is by tonnage and nothing to do with the packaging it is blamed for

belongs to the group

Plastic — material · the third, and the only commodity plastic that is more chlorine than carbon by mass

Sources

Material World
Our own writing
Wikidata
Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)

Questions this page answers

Where it comes from, and what it becomes

Follow Polyvinyl chloride back to what it starts as, and forward into what it becomes. Each step is a documented one — a real route material takes, not a chain of inference.

Upstream — what it comes from

Polyvinyl chloride → is sourced from (the chlorine arriving from chlor-alkali electrolysis of salt) → Chlorine → is produced by (at the anode) → Chlor-alkali electrolysis → takes as input (the largest single use of salt, and the process the whole chlorine and caustic soda industry rests on) → Salt → is produced by (in the solar route — the same process, read from the other end) → Brine evaporation → takes as input (the feedstock for solar salt and, in the salars, for the far stronger brines that lithium comes from) → Seawater
Polyvinyl chloride → is produced by (from vinyl chloride, itself made from the chlorine of chlor-alkali electrolysis) → Polymerisation → takes as input (as vinyl chloride, which is why more than half of PVC's weight is salt rather than oil) → Chlorine → is produced by (at the anode) → Chlor-alkali electrolysis → takes as input (as the brine the cell electrolyses, and as the source of the hydrogen that comes off the cathode) → Water → is sourced from (by desalination, where energy is cheap and coastline available — the only route that adds fresh water rather than moving it) → Seawater
Polyvinyl chloride → is sourced from (via ethylene dichloride and vinyl chloride — the chlorine comes from the chlor-alkali industry, and PVC is where about a third of world chlorine production ends up) → Ethylene → is produced by (the principal product, and the largest-tonnage organic chemical made anywhere) → Steam cracking → takes as input (the European and Asian cracker feed; North American crackers mostly run on ethane from natural gas instead, and make a different product slate as a result) → Naphtha → is sourced from (the fraction boiling between about 30 and 200 °C, separated by distillation rather than made) → Crude oil
Polyvinyl chloride → is produced by (from vinyl chloride, itself made from the chlorine of chlor-alkali electrolysis) → Polymerisation → takes as input (as tetrafluoroethylene, which is where a substantial share of industrial fluorine chemistry ends up) → Fluorine → is produced by (electrolysis of potassium bifluoride, which is molten and conducts — there is no chemical oxidant strong enough to displace fluorine from a compound, so electricity is the only route and always has been) → Molten salt electrolysis → takes as input (after concentration, as one of the two routes to lithium chloride) → Lepidolite
Polyvinyl chloride → is sourced from (the chlorine arriving from chlor-alkali electrolysis of salt) → Chlorine → is extracted from (by electrolysis of brine, which yields chlorine and sodium hydroxide together) → Halite
Polyvinyl chloride → is sourced from (the chlorine arriving from chlor-alkali electrolysis of salt) → Chlorine → is produced by (at the anode) → Chlor-alkali electrolysis → takes as input (as the brine the cell electrolyses, and as the source of the hydrogen that comes off the cathode) → Water → is sourced from (by desalination, where energy is cheap and coastline available — the only route that adds fresh water rather than moving it) → Seawater

These are the most distinct paths back. Polyvinyl chloride can be traced through others besides.

Downstream — what it becomes

Polyvinyl chloride → is used in (pipe, window frames, cladding and cable, which is where most of it goes) → Construction
Polyvinyl chloride → is an input to (pipe and window profile, which is most of what PVC is by tonnage and nothing to do with the packaging it is blamed for) → Extrusion