Effect of Beech bark Content on Physical and Mechanical Properties of Bark Flour-Polypropylene Composites

In this study, physical and mechanical properties of composites made of bark flour and polypropylene were studied and compared with those of wood flour-polypropylene composites. Bark flour content were adjusted at three levels (40, 50 and 60%) and compounded at absence and presence of 2% compatibilizer (MAPP) in a twin screw extruder to produce the bark flour-polypropylene composites. The wood flour-polypropylene composites also were manufactured at 60 filler weight wood flour loading. The results showed that water absorption and thickness swelling of composites containing bark flour increase with increasing bark flour content. The composites containing bark flour exhibited lower water absorption and thickness swelling than those made from wood flour. In absence of MAPP, bark content had no significant effect on flexural modulus of the composites but flexural strength and un-notched Izod impact strength significantly decreased with increase in bark content. The use of MAPP had no significant effect in increasing the mechanical properties. A comparison indicates that in absence of MAPP, bark flour-PP composites exhibited higher mechanical properties than wood flour-PP composite but in presence of MAPP, results were quite inversed.