Argus Embedded systems leading service provider in foam. Foam is a polyethylene foam filled with carbon (as are all black ESD foams),
giving it its conductive properties and color. Foam is designed for repeat use and will act as a Faraday cage when an item is fully enclosed within it.
A conductive foam will drain batteries if their contacts have a path the foam, so care must be taken static dissipative foam layer between the conductive foam and the item being packed). There are two grades of conductive foam: lead-insertion grade and component grade.
Lead-insertion grade conductive foam is designed to have components directly mounted into the foam via their leads and will drain charge off of attached components.
Anti-Static foam is a polyurethane foam that is chemically doped with an anti-static agent (surfactant) and colored with a pink dye for identification. An anti-static foam will not generate a static charge when it rubs against itself, but will happily pass a charge through itself to anything contained within (thanks to EEVblog for explaining that one).
Because anti-static foam does not provide shielding it must be placed within a shielding bag. Another key property of anti-static foam is that it has a shelf life when exposed to the environment. Thus it is usually used as a one-time foam for shipping components. It is the least expensive type of ESD foam. It has a surface resistance of 10^9 to 10^10 Ohms or less (the higher this number the more slowly a charge is dissipated).
There are many different types of foam available, and each has its unique characteristics and applications to meet customer requirements.