From the figure, the highest absorption rate was recorded by
water as the immersed solution followed by salt water, petrol,
engine oil and finally diesel. It was reported in [35] that it was possible
for natural fibres to uptake a large amount of water flow into
their fibre cell wall due to the fact that cellulose, lignin and hemicelluloses
posses polar hydroxyl groups which are highly attractive
to the hydrogen bonds of water. Absorption of water by the cell wall
of these lingnocellulosic fibres caused swelling of the cell wall, thus
increasing the absorption rate of the composite. On the contrary,
the polar hydroxyl groups are less attracted to solutions such as
diesel, petrol and engine oil. This contributed to low absorption rate
of the composite which may have been due to the trapped solution
in the hollow spots of the fibre’s outer surfaces embedded in the
matrix (c.f. Fig. 1). The effect of absorption rate on the different
types of solutions used concerning wear and friction performance
of T-OPRP composite will be discussed in depth in Section 4.