Effects of Composition Levels on the Cellular Structure and the Thermal Properties of Biodegradable Cushioning Extrudates

Abstract

Response surface methodology (RSM) was used to analyze the effect of polyvinyl alcohol (PVA) and calcium carbonate (CaCO3) on the cellular structure and the thermal properties of a biodegradable cushioning extrudate. A central-composite design (CCD) was used to develop models for the objective responses. The experiments were run at 105 C with a feed rate of 27.8 L/h, a screw speed of 500 rpm and a die diameter of 3.92 mm. The responses were most affected by changes in polyvinyl alcohol (PVA) levels and to a lesser extent by calcium carbonate (CaCO3) levels. The objective of this study is to focus on the composition levels affecting the cellular structure (average pore size) and the thermal properties (specific heat capacity and thermal conductivity) of extruded foams and to evaluate the possibility of using corn/PVA extrudates as packaging and insulating materials. The experimental results indicated that: 1. The cell sizes become smaller and more uniform and the cell walls become thinner with the increase in the PVA ratio. Moreover, using the CaCO3 also made the cell sizes become smaller and more uniform. 2. For all the treatments, the specific heat increased linearly as the temperature increased. 3. Several treatments have potential applications for thermal insulation because of their relatively high specific heat values and low thermal conductivity values.