Abstract: The present invention provides a wave absorber holding both nonflammability and flexibility and having advantageous properties regarding the lightness in weight, the thermal insulation, the sound insulation, the sound isolation, and the workability to ensure a certain freedom in shaping. Each of wave absorbing materials A1, A2, and A3 given as embodiments of the present invention include a conductive filler, an inorganic endothermic filler, and an organic binder as main constituents. A wave absorber A30 for wave anechoic rooms and semi-wave anechoic rooms is prepared by using any of these wave absorbing materials A1, A2, and A3.

Abstract: The present invention provides a method of treating waste magnetic tapes characterized in that waste magnetic tapes such as video tapes and cassette tapes are cut or crushed to a length of 1 to 50 mm, and heated at a temperature of 100.degree. to 200.degree. C. so that they are contracted in the form of curl, and a method of manufacturing building material boards characterized in that waste magnetic tapes such as video tapes and cassette tapes are cut or crushed to a proper size, heated, and then, supplied with a binder and molded under pressure.