INTRODUCTION: WOOD-PLASTIC COMPOSITES (WPC) ARE MATERIALS IN WHICH THE WOOD OR AGRO-BASED FIBERS OR FLOUR COMPOSE WITH A POLYMERIC MATRIX IN A MOLDING OR EXTRUSION PROCESS. ADDING COUPLING AGENT WILL LEAD TO BETTER BONDING BETWEEN THESE TWO MATERIALS. SEVERAL ADVANTAGES OF THESE PRODUCTS, INCLUDING: ACCEPTABLE STRENGTH, LOW WEIGHT AND ECONOMIC ISSUES HAVE CAUSED TO A RAPID GROWTH OF PRODUCTION AND CONSUMPTION. IN IRAN, SOME LOCAL MANUFACTURERS DEMONSTRATE THEIR FAVORITES FOR PRODUCTION OF THESE MATERIALS. THIS SHOWS THAT UNDERSTANDING THE BEHAVIOUR OF THESE PRODUCTS IS INTERESTING.