Application

Packaging

Keeping something intact, clean and saleable between the factory and the buyer — where roughly half of all plastic made ends up.

Packaging is a materials problem with an unusual objective function: the material has to protect the contents, survive distribution, carry printing, cost almost nothing, and then be thrown away. Nothing else is designed to be discarded as part of its specification.

That combination is why plastics took the market so completely. A glass bottle is inert, reusable and heavy; a steel can is strong and needs a coating; a plastic bottle is a tenth the weight, unbreakable, and shaped in one step from a preform that ships flat. Most of the environmental argument about packaging is an argument about which of those trade-offs was worth making.

Uses

Bottles, films, trays, closures, cans, cartons, cases and the pallets under them, in a hierarchy the trade calls primary, secondary and tertiary — what touches the product, what groups it, and what moves it.

Barrier performance decides most material choices and is invisible to the person holding the package. Oxygen ruins fat, moisture ruins biscuits, carbon dioxide escapes from a soft drink, and each of those is a different permeability requirement met by a different material — which is why so much modern packaging is a laminate of several, and why laminates are so hard to recycle.

Weight is the other governing constraint. A packaging material's carbon footprint is dominated by moving it, so a heavier material has to be substantially better at its job to be worth it — an argument glass frequently loses and occasionally wins on reuse.

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.

uses

Polyethylene terephthalate — material · the drinks bottle, which took the market from glass in about twenty years on weight and breakage alone
Polyethylene — material · film, bags and the majority of packaging by tonnage — the cheapest barrier there is against water
Polypropylene — material · food tubs and closures, which it took from polystyrene on temperature: it survives a dishwasher and a microwave
Polystyrene — material · as expanded foam for protective packing, and formerly for food service until a great many jurisdictions banned it
Soda-lime glass — material · inert, reusable and heavy, which is the whole trade-off — glass wins on reuse and loses on freight
Paper — material · cartons and cases, and the material most plastic packaging is now being asked to justify itself against
Aluminium — element · the drinks can and the foil laminate layer, where an impermeable barrier a few microns thick is worth the metal
ABS — material · rigid protective cases rather than disposable packaging — ABS is too expensive to throw away
PLA — material · food service disposables and film, sold on compostability that requires an industrial composter to deliver
5000 series aluminium alloy — alloy · the beverage can body, which is one of the largest single uses of aluminium there is
Aluminium beverage can — object · and the closed loop works because of the collection system rather than because of the metal
Plastic — material · roughly a third of all plastic by tonnage, and very nearly the whole of the public argument about the material

Sources

Material World
Our own writing

Questions this page answers

What is used for Packaging?

Where it comes from, and what it becomes

Follow Packaging 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

Packaging → uses (the drinks can and the foil laminate layer, where an impermeable barrier a few microns thick is worth the metal) → Aluminium → is extracted from (via alumina — bauxite is refined by the Bayer process before smelting) → Bauxite → is sourced from (the residue of prolonged tropical weathering, which strips the silica and alkalis out of an aluminosilicate rock and leaves the aluminium behind — basalt is one common parent among several) → Basalt → is sourced from (partial melting of mantle peridotite is what basalt magma is — the residue left behind stays peridotite, depleted of what went into the melt) → Peridotite → is composed of (the mineral that defines the rock and gives it its name — a peridotite is olivine-dominant by definition) → Olivine
Packaging → uses (film, bags and the majority of packaging by tonnage — the cheapest barrier there is against water) → Polyethylene → is produced by (from ethylene; chain length and branching decide whether it is a milk bottle or a fibre) → 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 brine; the salt is the feedstock for both products at once) → Halite
Packaging → uses (inert, reusable and heavy, which is the whole trade-off — glass wins on reuse and loses on freight) → Soda-lime glass → is produced by (drawn off the tin bath as a sheet flat on both surfaces) → Float glass process → takes as input (with difficulty, which is why flat borosilicate costs several times what window glass does) → Borosilicate glass → is produced by (with boron oxide replacing most of the soda, which is what drops the thermal expansion to a third and lets a hot dish go into water) → Glass melting → takes as input (as the stabiliser, and without it a soda-silica glass would slowly dissolve in water) → Limestone
Packaging → uses (the drinks bottle, which took the market from glass in about twenty years on weight and breakage alone) → Polyethylene terephthalate → is produced by (a condensation polymerisation rather than an addition one — the units join and release water, which is why the reaction runs in reverse when the polymer is processed wet) → 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 brine; the salt is the feedstock for both products at once) → Halite
Packaging → uses (food tubs and closures, which it took from polystyrene on temperature: it survives a dishwasher and a microwave) → Polypropylene → is produced by (polymerised from propylene with a Ziegler-Natta catalyst, which is what controls the arrangement of the side groups and so whether the product is a structural plastic or a gum) → 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 brine; the salt is the feedstock for both products at once) → Halite
Packaging → uses (as expanded foam for protective packing, and formerly for food service until a great many jurisdictions banned it) → Polystyrene → is produced by (straightforward addition polymerisation of styrene) → 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 brine; the salt is the feedstock for both products at once) → Halite

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