Characterisation of the microstructure and deformation of high modulus cellulose fibres

Abstract

This paper reports on the microstructure and deformation of one type of high modulus cellulose fibre characterised using the techniques of Raman spectroscopy and synchrotron X-ray diffraction and it compares this fibre to a lower modulus conventional viscose fibre. The crystallinity of the fibres has been determined using X-ray diffraction. The orientation parameter has been determined by measuring the width of the (200) equatorial reflections for each fibre using microfocus synchrotron radiation and it has also been shown that the crystal orientation parameter varies from the skin to core of the fibres and is different for each type. Mechanical properties of the fibres are reported and it is shown that the high modulus cellulose fibres have very different stress–strain behaviour to the viscose fibres. Finally, it is shown for the high modulus fibre that the 1414, 1260, 1095 and 895 cm−1 Raman bands shift under the application of tensile deformation towards a lower wavenumber with the 1095 cm−1 band giving information about the backbone chain stretching of the cellulose. The viscose fibres show less significant shifts in this peak. The crystal modulus of the high modulus cellulose fibre has also been determined by calculating the change in the c-spacing upon the application of tensile deformation to individual cellulose monofilaments. This change in the c-spacing is determined from the change in position of the (002) meridional reflection giving a crystal modulus of 77 GPa. This value is a little low compared to other published data, and reasons for this are discussed. The shear modulus between crystallites is also calculated and compared to previously published data.