Rheological Behaviour of PolypropylenelKenaf Fibre/Wood Flour Hybrid Composite

The hybridization of two types of short fibres having different lengths and diameters offers some advantages compared to each fibre being used alone in a single polymer matrix. In this study, the polypropylene/kenaf fibre/wood flour hybrid composites were prepared in an internal mixer. The temperature was 190°C and rotor speed was 60 rpm. The system was compatibilized by polypropylene grafted maleic anhydride. Based on dimensional aspects before and after processing, the kenaf as fibrous filler and wood flour as particulate filler were considered. The weight ratio of lignocellosic fillers was 40%. Dynamic rheological properties such as storage modulus, complex viscosity, damping factor were evaluated at 190°C. It was observed that, the non-linearity region of hybrid composites shifted to lower strains compared to virgin polypropylene. Due to higher probability of agglomerates formation in the sample containing 40% (by w1) of wood flour, the storage modulus and complex viscosity of this sample were higher than those of the other samples. A flattened section was observed in the tan 8 diagram which is attributed to different relaxation processes of composite and neat PP. The Cole-Cole diagrams of samples showed that the relaxation times shifted to higher values with the addition of fillers and the longest relaxation times were related to compos ites with pure wood flour.