I'm interested in the composition material of standard, clear plastic
jewel cases.  I've seen contradicting listings saying that they are
composed of either Polyethelyne, polyvinyl chloride (PVC), and
polypropolene.  Thanks.

Hi dekan,

As mister2u speculated, it's polystyrene.

References:

Answer to a similar question posted on the Plastics & Rubber Advisory
Service (PRAS) Questions & Answers Forum on the British Plastics
Federation website.
http://www.bpf.co.uk/answers.cfm?question_id=875

A news release from Dow Chemical says "Now in its third decade of use,
the polystyrene jewel box has achieved a high level of consumer
confidence."
http://www.dow.com/dow_news/prodbus/2002/20020903b.htm

A review of DiscSavers CD cases on the Dan's Data website says "your
ordinary CD jewel case is made out of polystyrene."
http://www.dansdata.com/discsavers.htm

Media Heaven description of Standard CD jewel case
http://www.mediaheaven.co.uk/jewel-case.htm

Media Sciences FAQ answer on jewel cases
http://www.mscience.com/faq22.html

More than you ever wanted to know about polystyrene
http://www.polystyrene.org/polystyrene_facts/facts.html


If you need any more information about this, please ask for a clarification.

Regards,

--efn

Even more mysterious question is who puts jewels in them?

Did anyone guess acrylic?

Injection moulding is the process that moulds plastic through heat and
pressure, by injecting molten plastic polymer into the desired mould.

Injection moulding is the most commonly used process for moulding
plastics because it gives a good surface finish and can be used for
very complex mouldings. Injection moulding, although requiring a
substantial capital investment, becomes very economically viable in
mass production and gives a very low unit production cost. Injection
moulded plastics are invariably thermoplastics because thermosetting
plastics assume their final shape through heat and so can not be
moulded with this process.

Familiar products manufactured by injection moulding include: computer
enclosures, milk crates, CD cases and mobile phones.

The plastics that are used in injection moulding include: polythene,
low density polyethylene (LDPE), high density polyethylene (HDPE),
polystyrene (PS), polypropylene (PP) and acrylonitrilebutadienestyrene
(ABS).
It's probably polystyrene(the others are flexible)