Structure of kapok fibre
Kapok fibre wall is different from that of cotton fibres both in the lateral and the longitudinal sections of the fibre. The cell wall is divided into five basic walls or layers: an outer skin S, a primary wall W1, secondary wall W2, tertiary wall W3 and an inner skin IS. IS is thin (40–70 nm) and acts as a protective layer for the fibre. W1 is thicker than S, but thinner than both W2 and W3 its thickness varies from 160 to 240 nm, with an average of about 200 nm. The thickness of W2 is about 500 nm, which is similar to that of W3. The inner skin IS is very thin and uneven in thickness, with an average thickness of about 40 nm that could be distinguished easily in the cross-sections. Additionally, there were transition layers L1 and L2, observable between W1 and W2 and between W2 and W3 respectively.
The fig 2.1 and 2.2 shows SEM and TEM images of kapok fibre respectively.
Kapok fibres are characterized of having high levels of acetyl groups (13.0%). Usually cell walls
of plants contain about 1%–2% of acetyl groups attached to non-cellulosic polysaccharides.
Kapok fibre are significantly super hydrophobic and do not get wet with water