Expanded EVA / PE closed-cell foam or sponge is usually made out of a blend of Ethylene Vinyl Acetate copolymer (also known as EVA) and polyethylene. The product is a lightweight foam material which has a smooth surface and does not absorb water. Generally EVA sheeting is priced competitively, compared with other blown materials and is available in different densities, thicknesses and colours.
It is one of the materials most popularly known as expanded rubber or foam rubber sheeting.
EVA foam is used to produce - among others - mouse pads, flip flops and sports mats. Sheets of the material can be used for manufacturing Participatory 3D Models.
Models made out of this material are well suited for humid tropical environments where carton board may deteriorate rapidly.
Manufacturing a 3D model using 'expanded EVA / PE closed-cell foam' compared to carton board implies a slightly higher cost and non biodegradable debris, but ensures a more durable output and a consistent vertical scale/exaggeration of the 3D model. Insertion of map and push pins is easy.
More information on the topic is found here.