Raman spectroscopy of stressed high modulus poly( p-phenylene benzobisthiazole) fibres

Abstract

A Raman microscope has been used to investigate the deformation of high modulus poly( p-phenylene benzobisthiazole) (PBT) fibres. The structure of the fibres has been characterized using wide-angle X-ray diffraction and their mechanical properties have been determined using standard fibre tensile testing methods. It has been found that the as-spun fibres have a modulus of about 160 GPa and that this increased to about 240 GPa following heat treatment. This increase in modulus is accompanied by an improvement in structural order. Well-defined, intense Raman spectra can be obtained from individual fibres and three main bands at 1175, 1480 and 1600 cm −1 have been identified. It has been found that all bands are strain sensitive with the 1480 cm −1 band being the most sensitive, moving by −1 12.1 ± 0.6 cm −1/% strain for the heat-treated fibres. The reasons for the strain sensitivity of the Raman bands is discussed in relation to deformation of the bonds in the individual PBT molecules. The possibility of using the strain-induced band frequency shifts to follow the micromechanics of deformation in composites reinforced with PBT fibres is discussed.