CD jewel case

Rigid polystyrene is moulded into clear protective panels for a CD.

CD jewel case, illustrative image

Material

Clear case panels: PS

Material selection rationale

Clarity
Leaves the disc or paper insert visible.
Rigid detail
Hinges and closing features can be moulded into the panels.
Notch sensitivity
A rigid clear lid can protect a flat disc while its small hinge remains vulnerable to cracks; toughness and hardness describe different behaviour.

How it becomes a product

  1. Mould the panels: Clear PS is injection-moulded into the lid and base. The lid’s hinge features form in the tool before it is connected to the base; they are not a flexible PP-style living hinge.
  2. Assemble: The cooled panels are joined with the tray and paper inserts as required.

Preparation routes

Styrene route

Addition polymerisation. The vinyl groups join into a carbon backbone carrying phenyl side groups. Making foam is a later processing choice, not a second polymerisation reaction. The benzene ring is retained as a side group rather than opened into the growing chain. Solid PS and expanded PS therefore share this molecular route.

Initiation and temperature control support chain growth. Expandable grades also contain a blowing agent, which is not a monomer; rubber-modified grades have additional polymer content. Rubber addition or bead expansion changes material structure beyond this simple backbone trace.

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

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

Sources

  1. Standard CD jewel case: polystyreneHama
  2. Polystyrene: from benzene and ethene to solid and expanded productsChemical Industry Education Centre, University of York