ABS

A rigid, impact-modified plastic used in toy bricks, keycaps and printed parts.

Also known as
acrylonitrile butadiene styrene, ABS plastic

In everyday products

Structure and behaviour

Styrene–acrylonitrile matrix + butadiene-derived rubber phase

ABS has rubbery butadiene-derived domains in a styrene–acrylonitrile-rich matrix, with grafting helping connect the phases. It cannot be described faithfully by one fixed three-monomer alternating repeat unit.

  • The relatively rigid matrix holds fine features such as brick studs and keycap stems.
  • Rubbery domains help absorb deformation around a developing crack, improving impact behaviour over an unmodified rigid styrenic plastic.
  • Monomer proportions, rubber particle structure and additives alter the balance of stiffness, finish and toughness.
  • Injection moulding replicates a tool; filament printing builds layers with different interlayer and in-layer behaviour.
  • Compared with ordinary PLA filament, ABS tolerates higher-temperature applications but is more demanding to print without distortion.

Preparation routes

Three-monomer route

Multistage addition and graft polymerisation. A representative emulsion route first makes butadiene-derived rubber particles, then polymerises styrene and acrylonitrile with grafting onto the rubber. A styrene–acrylonitrile matrix surrounds the rubber phase. The staged route produces a multiphase material rather than a regularly alternating A–B–C chain. The rubber phase and matrix explain the combination of toughness and rigidity.

Initiators, emulsifiers and process control support the stages. The three monomers are all part of the material's origins, not interchangeable options or a claim that they are charged at once. A different ratio or particle structure produces a different grade even when all three monomer names stay the same.

  1. ABS: monomers and manufacturing routesINEOS
  2. Reference document on best available techniques in the production of polymersEuropean Commission, Joint Research Centre · 2007

From benzene and ethene to styrene

  1. Benzene + Ethene → Ethylbenzene

    Alkylation joins an ethyl group to the benzene ring. Both feedstocks belong to this step.

  2. Ethylbenzene → Styrene

    Dehydrogenation removes hydrogen and creates the vinyl double bond used in the next polymerisation step.

  1. Polystyrene: from benzene and ethene to solid and expanded productsChemical Industry Education Centre, University of York

From propene to acrylonitrile

  1. Propene + Ammonia + Oxygen from air → Acrylonitrile

    Propene reacts with ammonia and oxygen over a catalyst to produce acrylonitrile. The three-carbon feedstock becomes a molecule containing both C=C and C≡N groups. Nitrogen is supplied by ammonia; this industrial conversion is different from extending a halogenoalkane chain with cyanide ions. Product separation removes co-products including acetonitrile and hydrogen cyanide.

  1. Lima: acrylonitrile manufacture from propene, ammonia and airINEOS Nitriles
  2. The Sohio acrylonitrile processAmerican Chemical Society

Material limits

An ABS part is not automatically UV-stable or suitable for an elevated-temperature load. Printing needs control of cooling, enclosure conditions and ventilation; colour alone reveals none of those choices. Mixed resins, coatings and attached electronics complicate recovery, so keep an ABS shell distinct from the complete assembled product.

Sources

  1. ABS: monomers and manufacturing routesINEOS
  2. Materials used in building elementsLEGO Group
  3. Low Profile ABS LSA Full Set KeycapsKeychron
  4. ABS printing: mechanical parts, shrinkage and process limitationsPrusa Research
  5. Sustainable plastics: the role of chemistryRoyal Society of Chemistry