Generally, single-used foam packaging is used by manufacturers to protect and preserve a wide array of food and industrial products. Expanded polystyrene (EPS) is used extensively in single-use packages due to its low density, thermal insulation, strength and low cost (Alliance of Foam Packaging Recyclers (AFPR), 1999). The objective of this study is to focus on the process variables (feed composition, die temperature and screw speed) affecting the cellular structure and the thermal properties of extrudates and to evaluate com/PVA extrudate as packaging material. The experimental results indicated that the cell size became smaller and uniform; moreover, the cell wall thickness became thinner with the increase in die temperature and screw speed. Moreover, increasing the PVA ratio ranged from 5% to 30% also made the cell sizes became smaller and uniform. The corn granules blended with 15% PVA (Treatment 26) have potential applications as thermal insulation for their high specific heat values. The formulation with 15% PVA (Treatment 26) had the highest specific heat. For all formulations, the specific heat increased linearly as the temperature increased. (c) 2004 Elsevier Ltd. All rights reserved.