Structure-Property Relationships in Natural Cellulosic Fibres Part Ⅱ: Fine Structure and Tensile Strength

摘要

This is the second in a series of research papers featuring structure- property relationships in natural cellulosic fibres, mainly focussed on flax fibres originating from the straw-waste product from linseed-oil production. This part gives an insight into the fine structure of natural fibres as examined by light and electron microscopy in conjunction with X-ray-diffraction techniques and the difficulties associated with the measurement of tensile strength by both the single-fibre and the fibre-bundle techniques. The information gained by light microscopy (LM) is supplemented by scanning electron microscopy (SEM) and by X-ray diffraction (XRD). XRD results obtained by both photographic and diffractometric methods reveal the extent of crystallinity and orientation in the fibres. The information is available for assistance in understanding the physico-mechanical properties such as tensile strength, together with absorption and degradation characteristics, in order to utilise natural fibres most effectively for new end-uses. It is shown that different parameters, such as the stage at which the fibre was harvested, the degree of retting, and the mechanical or chemical processing carried out, have to be taken into consideration before quoting any final figure for fibre tensile strength. A large number of measurements have to be made in order to reduce the degree of variability and obtain a reliable and reproducible value with a low standard deviation. It is also concluded that the single-fibre test gives more accurate results than fibre-bundle tests, since the former makes no assumption regarding the cross-section of the fibres and the number of ultimate fibres actually present in a bundle.