EPP Foam – Why use it?

A customer asked me to make a custom insert for 2 of this small flowmeter package. Sure, no problem except that they wanted EPP (Expanded Polypropylene) foam, and I have only used EPE (Expanded Polyethylene) before. Well, they had to have EPP, so I researched the differences between the two types of foam and found out that EPP is substantially more chemical resistant than EPE, so I got to learn something. The EPP was very expensive compared to what I usually use and I had to special order it, but the job got finished and the customer was happy.