RF Absorbing Materials?

I'm researching the tech specs for the iphone, because I would love to design a case for mine. however, I wonder about the potential to resell this to customers with a model which is open for purchase and customization.

According to this (from apple) there are certain materials you should not use:

Cases for Apple devices should not contain materials or coatings that absorb radio frequency energy. Such materials can impair or degrade the performance of cellular communication antennas or GPS, WiFi, or Bluetooth antennas. Examples include (but are not limited to) the following:
Metals (e.g. steel, aluminum, magnesium, titanium, etc.) Plastics with any carbon content Plastics with any glass content Plastics with metallic plating
Metallic paints Black paints with high carbon loading White paints with high titanium dioxide loading Metallic Physical Vapor Deposition (PVD) coatings

********************************
Newbie question here - are the materials available at shapeways safe for this purpose?

********************************

You should be fine with plastics. Just stay away from metals and alumide, to be safe.

That's just hilarious. They probably meant "metalic" content.

Almost by definition.. ANY plastic is a long-chain hydroCARBON molecule.

This is absolutely wrong. I'm an RF engineer and have measured the properties of most rapid prototyping materials.

From shapeways, only their WSF is acceptable. Everything else is incredibly lossy and will cause reception problems/dropped calls.

However, due to the porosity of WSF, it will absorb water and will become lossy over time. It needs to be sealed with an appropriate sealant.

Or maybe they mean plastics with carbon fibre reinforcement? Just like they mention "Black paints with high carbon loading" too.

The machines used for WSF can work with CarbonMide, carbon-fibre filled polyamide 12. Or with a glass filler, as PA 3200 GF.

PS: PrimePart DC or PrimeCast 101... ^_^