Q: I ordered some vinyl disc binders and it looks like they are cracking along the spine. Why is this happening?
A: Most vinyl media packages have two types of vinyl: a hard inner layer that protects the media and a soft, flexible exterior. When exposed to changes in temperature (particularly when exposed to colder temperatures), the soft vinyl will expand and contract, while the stiffer vinyl doesn't expand or contract as much. The end result: a cracked spine. (Ouch!)
Dean Engel answers real questions from Polyline customers regarding disc publishing equipment, discs and media packaging.
Can CD jewel cases melt in a library drop box?
Q: Some libraries claim that their CD cases melt due to high temperature if they were left in a drop box for couple of days. Is that true? What is the melting temperature of a CD case?
A: Traditional CD cases are made of polystyrene, which has a melting temperature of around 374-500° F (190-260° C). Temperature can be an issue for polystyrene, but not because of its melting temperature; it's because of something called "glass transition temperature." This basically means the temperature at which a polymer turns from something that's hard and brittle to something that's soft and bendy.
A: Traditional CD cases are made of polystyrene, which has a melting temperature of around 374-500° F (190-260° C). Temperature can be an issue for polystyrene, but not because of its melting temperature; it's because of something called "glass transition temperature." This basically means the temperature at which a polymer turns from something that's hard and brittle to something that's soft and bendy.
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