Expandable-polymer-particle material comprising at least one thermoplastic polyurethane (TPU) with Vicat softening point (in accordance with ISO 306/ASO) below 80° C. and from 5 to 95% by weight of at least one polymer obtainable via free-radical polymerization, based on the entirety of TPU and of the polymer obtainable via free-radical polymerization, where the polymer obtainable via free-radical polymerization has been bonded to the TPU in a manner that gives a comb polymer, graft polymer, or copolymer, is suitable for the production of moldings, in particular for use as insulation material.