The invention relates to a spacing device substantially consisting of flexible structural supporting elements comprising open arches which are arranged near each other and one after another according to a grid pattern above a base plane and openings which are arranged according to a corresponding grid pattern and pass through the base plane at least below the arches. In a low-load interval, the feeding mass flow is increased with increasing load while the circulating mass flow is kept substantially constant, in a moderate load interval the feeding mass flow is further increased with increasing load and the circulating mass flow is reduced to zero. 01 to 15 percent, oligomers in an amount of 0. A concavo-convex cooperating structure is defined in the immovable portion and the movable portion to ensure the receiving structure being capable of receiving the heat pipe precisely.