Effect of Atmospheric Air Pressure Plasma Treatment on the Thermal Behaviour of Natural Fibres and Dynamical Mechanical Properties of Randomly-Oriented Short Fibre Composites

The effect of atmospheric air pressure plasma (AAPP) on the dynamical-mechanical properties of randomly-oriented short lignocellulosic fibre-reinforced/cellulose-acetate-butyrate (CAB) composites was investigated. In addition, the thermal behaviour of the lignocellulosic fibres before and after AAPP treatment was investigated in order to quantify the thermal resistance of the modified fibres. A significant increase in the thermal resistance, i.e., onset of thermal degradation in air, of AAPP-treated lignocellulosic fibres as compared to the untreated fibres was found. The dynamical mechanical thermal analysis of the composites showed, as expected, that the incorporation of 30 wt% untreated lignocellulosic fibres into CAB leads to an increase of the storage modulus, which increases significantly further with the incorporation of AAPP-treated lignocellulosic fibres in to the matrix. The glass transition temperature of CAB as determined by DMTA was 120 degrees C and remained unaffected by the incorporation of (untreated) fibres but increases slightly to approximately 125 degrees C for all composites reinforced by AAPP-treated fibres. The slight increase in the mechanical glass transition temperature and the reduction in the mechanical damping (tan delta) might be an indication of an improvement in fibre-matrix bonding in the composites containing AAPP-treated fibres.