A mixt. contg. polyethylene, foaming agent, crosslinking agent, antioxidant and flame retardant was extruded as a granulate and as a film, crosslinked at 160 degrees C for 4 min, formed at 225 degrees C for 1.5 min and studied for apparent d., tensile strength and elongation at max. stress. The formed film quality met the std. requirements for packaging.