The study of fibre/matrix bond strength in short hemp polypropylene composites from dynamic mechanical analysis

This paper presents results from an experimental study on the static and dynamic mechanical and viscoelastic properties of short hemp fibre polypropylene composites. Composites containing 10-60 wt.% short noil hemp fibre were injection moulded. The maleic anhydride grafted polypropylene (MAPP) and maleic anhydride grafted Poly(ethylene octane) (MAPOE) were used as coupling agents for modifying the matrices. Dynamic mechanical thermal analysis (DMTA) of the composites were performed over a temperature range of 25-150 °C under frequency of 1 Hz. DMTA revealed no noticeable changes in α-transition temperature when the fibre content was increased or coupling agents were added. The composites revealed better temperature resistance at higher fibre content. However, the increase in storage modulus was negligible in composites reinforced with more than 40 wt.% hemp fibres; due to the agglomeration of the fibres. The results of the damping ratio analysis revealed that higher interfacial bonding was achieved by addition of MAPP coupling agent in comparison with addition of MAPOE coupling agent. This was also confirmed by tensile strength experiments and scanning electron microscope (SEM) observations.