EXTRUSION FOAMING OF CELLULOSE FIBER REINFORCED POLYPROPYLENE COMPOSITES

摘要

This paper investigates the effect of polypropylene type and cellulose content on the foaming behaviour of cellulose fiber reinforced polypropylene composites in extrusion. Two types of polypropylene (linear and branched structures) are used as a polymer matrix. The thermal properties of the composites are characterized by a differential scanning calorimeter (DSC), and the viscosity of the composites is evaluated by a rotational rheometer. The foaming behaviour of the composites is examined using an extrusion foaming system, in which carbon dioxide (CO2) is used as a physical blowing agent for foams. The results suggest that with the increase of cellulose content, the cell density increases, whereas the void fraction decreases, but only up to a cellulose content of 20 wt%. When the cellulose content is increased to 40 wt%, the void fraction then increases. The results also indicate that the two types of polypropylene have a minimal effect on the foaming behaviours of the cellulose fiber composites.