The preparation of Phase Change Materials (PCM) with improved thermal conductivity, based on linear low-density polyethylene (LLDPE), paraffin wax with a melting point of approximately 42 degrees C and expanded graphite as well as the investigation of their physical behavior is reported in this paper. The absorption of heat energy is realized by phase transitions in the wax structure, i.e., solid solid transitions between different crystalline structures of wax and, primarily, by a solid liquid transition. An estimate of the total heat energy that can be reversibly absorbed or released by the designed materials was determined using Differential Scanning Calorimetry (DSC). The improvement in the thermal conductivity of the polymeric materials was obtained by incorporating expanded graphite into the blends. Expanded graphite has a reinforcing effect on the PCM, resulting in an increase in the toughness (Young's modulus) Significant amounts of wax are leached from the samples, and a higher wax content also results in more wax leakage. Graphite significantly reduces the wax loss from the samples. (C) 2015 Elsevier B.V. All rights reserved.