Visualisation of dislocations in hemp fibres: A comparison between scanning electron microscopy (SEM) and polarized light microscopy (PLM)

Dislocations are areas of the cell wall in natural fibres where the direction of the microfibrils (the microfibril angle) differs from the microfibril angle of the surrounding cell wall. Such regions affect the quality of natural fibres for industrial use. Dislocations may be studied using a number of techniques, and in this study two of them were compared: scanning electron microscopy (SEM) and polarized light microscopy (PLM). Images are presented that show exactly the same dislocations using these two techniques. The comparison showed that dislocations are more numerous and more clearly visible in images from PLM than in images from SEM, as dislocations are only seen in SEM if they are so large that they result in topographical changes of the fibre surface, i.e. a buckling of the S1 wall or a folding of the whole cell wall. However, for such large dislocations details are seen in the cell wall using SEM, while only a large bright region is seen in PLM.