The present invention is concerned with a material comprising: a matrix material comprising a plurality of urethane and/or urea and/or isocyanurate groups and having a hardblock content of more than 75% (hereinafter called matrix A); and a polymeric material which 1) has no groups which are able to form a urethane, urea or isocyanurate group with an isocyanate group, 2) exhibits a phase change as measured by differential scanning calorimetry (DSC) in the temperature range −10° C. to +60° C. with an enthalpy ΔHm of at least 87 kJ/kg, 3) is interpenetrating said matrix A, and 4) has an average molecular weight of more than 700 and comprises at least 50% by weight of oxyalkylene groups, based on the weight of this material, wherein at least 85% of the oxyalkylene groups are oxyethylene groups (hereinafter called polymeric material B); and wherein the relative amount of said matrix A and of said polymeric material B, on a weight basis, ranges from 15:85 to 75:25. Process for preparing such material.