This paper mainly includes the preparation of a novel form-stable composite phase change material (PCM) by incorporation of lauric acid (LA) within the expanded perlite (EP), characterization of the composite by SEM and FT-IR techniques and determination of thermal properties and thermal reliability of the composite PCM using DSC analysis. The LA could be retained by 60 wt.% into EP without melted PCM seepage from the composite and therefore, this composite was described as form-stable composite PCM. SEM results showed that the LA confined into porous of EP. FT-IR analysis indicated that the composite formation of porous EP and LA was physical. The melting and freezing temperatures and latent heats of the composite were measured as 44.13 degrees C and 40.97 degrees C; 93.36 J/g and 94.87 J/g, respectively, by DSC analysis. Thermal cycling test showed that the form-stable composite PCM has good thermal reliability and chemical stability although it was subjected to 1000 melting/freezing cycling. Besides, thermal conductivity of the composite PCM was increased approximately as 86% by adding 10 wt.% expanded graphite (EG). As a result, this composite PCM could be considered to have good potential for thermal energy storage because of its good thermal energy storage properties, thermal and chemical reliability and thermal conductivity. (C) 2009 Elsevier B.V. All rights reserved.