Rheological properties of polypropylene/hemp fiber composites

This study investigates the effect of hemp fibres on the shear and elongational rheology of polypropylene (PP). The parameters studied were hemp content (0‐30%) and maleic anhydride polypropylene (MAPP) addition (0‐0.6%). Shear rheology revealed that fibre content mainly influences low shear rate properties like yield stress and zero‐shear‐viscosity while coupling agent addition mainly influences intermediate to high shear rate parameters like relaxation time, power‐law index and Yasuda parameter. On the other hand, elongational rheology results showed a strain softening behaviour of the composites with increasing consistency and decreasing strain at break as fibre concentration increases. MAPP addition is also shown to improve the fibre‐polymer compatibility, but at the same time produces a plasticizing effect having a significant effect on rheological properties. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers