Effect of Clay on Extrusion Foaming of Wf/PP/Clay Composites Using N2

The paper investigated the effect of clay on extrusion foaming of polypropylene (PP)/clay composites and wood fiber (WF)/PP/clay composites that contained a small amount of clay, up to 5 wt%. The composites were prepared by a melt blending masterbatch process. The clay dispersion in the composites was characterized by a X-ray diffractometer while the viscosity of the composites was evaluated by a rotational rheometer. The foaming behaviour of the composites was examined using an extrusion foaming system, in which N₂ was used for foams as a physical blowing agent. The results suggested that the organoclay provided higher cell density for PP/clay composites than the natural clay, and the addition of organoclay was more effective in improving the cell morphology (decrease of cell size and more uniform cell size) for the WF/PP/clay composites with lower fiber loading.