Preparation and morphology of polypropylene/wood flour composite foams via extrusion

In this study, polypropylene (PP)/wood flour composites foams with an average cell size lower than 100 μ were successfully produced by extrusion. The effects of the coupling agent (maleated PP), wood flour content (20%, 30%, and 40% weight), initial wood moisture, and blowing agent content on the cell structure are reported. It was found that the addition of a coupling agent increases the blowing agent efficiency and helps to reduce the density of the composites. Moreover, wood moisture appears to be an effective secondary blowing agent under specific conditions. POLYM. COMPOS., 26:731–738, 2005.