EPP Foam
Expanded Polypropylene, also known as EPP, is an engineered plastic foam material. This foam is extremely durable and lightweight, because it is made out of little bubbles of CO2 and polypropylene resin. This type of RC foam is inexpensive to manufacture, making the price of the airplane usually lower also. This foam will withstand even the hardest crashes.
Elapor Foam
With the increase of DIY airplanes, many RC fanatics are complaining that EPP foam is not mold-able. Elapor foam is made primarily out of Styrofoam; so, while it isn't the most durable, it is able to twist and turn into new things unlike its EPP sister. If you are looking for a somewhat tough, flexible foam, than Elapor may be the choice for you.
EPO Foam
Expanded Polyolefin is a durable, flexible, and adhesive-friendly foam made primarily for RC gliders. It is both durable and lightweight, but it is quite expensive as it isn't the standard foam used by companies. Expanded Polyolefin (EPO) is ready, however, to take any kind of glue, tape or finish needed for the touch-ups on your airplane. The EPO foam is a great all-around performer for your airplane.