Material · Synthetic

ABS

Three monomers doing three jobs — the tough, opaque plastic of appliance housings, car interiors and the LEGO brick.

ABS is not a single polymer but a two-phase material: rigid styrene-acrylonitrile with particles of polybutadiene rubber dispersed through it. Each component does one job — styrene gives rigidity and gloss, acrylonitrile gives chemical resistance and heat tolerance, butadiene gives impact toughness — and the ratio is adjusted grade by grade.

The rubber phase is what makes it tough rather than brittle. A crack propagating through the matrix meets a rubber particle, which stretches and absorbs the energy instead of letting the crack run. Polystyrene without that phase shatters; ABS does not.

It is amorphous, so it has no melting point. It softens over a range around 105 °C, which is why an ABS part deforms in a hot car and why boiling water in an ABS cup is a bad idea.

Processing

Injection moulded, above all — it flows well, reproduces fine detail and holds tight tolerances, which is why it is the LEGO brick. Also extruded as sheet for thermoforming, and used as a filament in desktop 3D printing, where its tendency to warp as it cools makes it markedly harder to print than PLA.

It takes electroplating better than almost any other plastic. The butadiene phase can be etched away chemically to leave a keyed surface, so chrome-plated plastic trim is nearly always plated ABS.

Uses

Appliance housings, power tool bodies, vacuum cleaners, keyboard keycaps, luggage, car interior trim and instrument panels, pipe fittings, and the LEGO brick — which is the demonstration piece, moulded to a few micrometres so that bricks from different decades still fit.

It sits where polystyrene is too brittle and polycarbonate too expensive, and that is most of the consumer durables industry.

History

Developed in the 1940s and commercialised in the early 1950s, as an answer to polystyrene's brittleness. LEGO switched from cellulose acetate to ABS in 1963, and the reason was dimensional stability rather than strength: acetate bricks absorbed moisture, changed size and lost their clutch, so older sets stopped working with newer ones. ABS does not, which is why the compatibility guarantee has held since.

Environmental impact

Recyclable in principle as a thermoplastic, and rarely recycled in practice, because it arrives in complex assemblies bonded and screwed to other materials rather than in a clean sorted stream. Electronics recycling recovers it where separation is economic.

It degrades under ultraviolet light — yellowing and embrittling — which is why old computer cases go beige and why outdoor ABS is either pigmented, stabilised, or replaced by something else.

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.

is sourced from

Styrene — compound · one of the three monomers, supplying rigidity and gloss to the continuous phase

contains

Carbon — element · the backbone of all three monomers
Hydrogen — element · the balance
Nitrogen — element · in the acrylonitrile, and the source of the chemical and heat resistance the other two do not supply

is produced by

Polymerisation — process · styrene and acrylonitrile polymerised in the presence of polybutadiene rubber, so the rubber phase is grafted in rather than blended

is an input to

Injection moulding — process · the standard material for a moulded housing, and the LEGO brick's tolerance is the demonstration of what the process can hold
Mechanical recycling — process · recovered from electronics where separation is economic, and otherwise lost inside assemblies

is used as

Additive manufacturing — application · tougher and more temperature-tolerant than PLA, and markedly harder to print because it warps as it cools
Packaging — application · rigid protective cases rather than disposable packaging — ABS is too expensive to throw away

is an alternative to

Polystyrene — material · ABS is polystyrene with a rubber phase and acrylonitrile added, and it won the durable-goods market on the toughness that gives it
Polycarbonate — material · in housings: polycarbonate is stronger and more heat resistant, ABS is cheaper and moulds more easily, and blends of the two are common precisely because the trade is close
Zinc die-casting alloy — alloy · the competition for a small moulded component: zinc gives weight, heat resistance and shielding, and ABS gives cost and colour

succeeded

Phenolic resin — material · in consumer goods: thermoplastics took the housings, the radios and the telephones on colour, toughness and moulding speed, and phenolic retreated to the places where not melting is the point

is used in

Automotive manufacture — industry · interior trim and instrument panels, and plated ABS for anything that looks like chrome and is not

is used to make

Transistor — object · not the device but the package and the board hardware around it — the plastics are most of what a reader actually handles

belongs to the group

Plastic — material · the durable-goods plastic — housings, tools and the LEGO brick

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 ABS 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

ABS → is produced by (styrene and acrylonitrile polymerised in the presence of polybutadiene rubber, so the rubber phase is grafted in rather than blended) → 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
ABS → is sourced from (one of the three monomers, supplying rigidity and gloss to the continuous phase) → Styrene → is sourced from (via ethylbenzene: ethylene alkylates benzene, and the product is dehydrogenated) → 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
ABS → is produced by (styrene and acrylonitrile polymerised in the presence of polybutadiene rubber, so the rubber phase is grafted in rather than blended) → 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
ABS → is sourced from (one of the three monomers, supplying rigidity and gloss to the continuous phase) → Styrene → is produced by (by way of ethylbenzene, which is ethylene and benzene joined and then dehydrogenated) → 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
ABS → is produced by (styrene and acrylonitrile polymerised in the presence of polybutadiene rubber, so the rubber phase is grafted in rather than blended) → Polymerisation → takes as input (as vinyl chloride, which is why more than half of PVC's weight is salt rather than oil) → Chlorine → is extracted from (by electrolysis of brine, which yields chlorine and sodium hydroxide together) → Halite
ABS → is produced by (styrene and acrylonitrile polymerised in the presence of polybutadiene rubber, so the rubber phase is grafted in rather than blended) → Polymerisation → takes as input (as tetrafluoroethylene, which is where a substantial share of industrial fluorine chemistry ends up) → Fluorine → is extracted from (the only significant source; hydrofluoric acid is made from it and everything fluorinated follows) → Fluorite

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

Downstream — what it becomes

ABS → is used to make (not the device but the package and the board hardware around it — the plastics are most of what a reader actually handles) → Transistor → is used in (the component every other modern technology is assembled from, and one nobody ever sees) → Electronics manufacture → is associated with (and the supply chain it produced is the deepest and most concentrated in the world economy) → The semiconductor era complete chain
ABS → is an input to (the standard material for a moulded housing, and the LEGO brick's tolerance is the demonstration of what the process can hold) → Injection moulding
ABS → is an input to (recovered from electronics where separation is economic, and otherwise lost inside assemblies) → Mechanical recycling
ABS → is used as (tougher and more temperature-tolerant than PLA, and markedly harder to print because it warps as it cools) → Additive manufacturing
ABS → is used as (rigid protective cases rather than disposable packaging — ABS is too expensive to throw away) → Packaging
ABS → is used in (interior trim and instrument panels, and plated ABS for anything that looks like chrome and is not) → Automotive manufacture

These are the most distinct paths onward. ABS ends up in others besides.