Keyboard keycaps
ABS is moulded into the small shells pressed by a typist's fingers.
Material
Keycap body: ABS
Material selection rationale
- Detailed moulding
- Forms the top surface, thin walls and switch attachment.
- Rigid and light
- The shell holds its shape without adding much moving mass.
- Stem and surface serve different jobs
- The internal stem must fit a switch, while the outside carries texture and a legend. Wear of the legend need not mean the ABS body failed.
How it becomes a product
- Mould the shell: ABS fills a keycap mould and cools around the required internal geometry. Moulding fixes wall thickness and stem geometry; the selected legend process is a separate design choice.
- Add the legend: Lettering is printed, marked or made with a further moulding step, depending on the keycap design.
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.
- ABS: monomers and manufacturing routesINEOS
- Reference document on best available techniques in the production of polymersEuropean Commission, Joint Research Centre · 2007
From benzene and ethene to styrene
- Benzene + Ethene → Ethylbenzene
Alkylation joins an ethyl group to the benzene ring. Both feedstocks belong to this step.
- Ethylbenzene → Styrene
Dehydrogenation removes hydrogen and creates the vinyl double bond used in the next polymerisation step.
- Polystyrene: from benzene and ethene to solid and expanded productsChemical Industry Education Centre, University of York
From propene to acrylonitrile
- 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.
- Lima: acrylonitrile manufacture from propene, ammonia and airINEOS Nitriles
- The Sohio acrylonitrile processAmerican Chemical Society