Deformation studies of thermotropic aromatic copolyesters using NIR Raman spectroscopy

Near infrared (NIR) Raman spectroscopy has been used to investigate the deformation behaviour of highly oriented fibres and tapes made from thermotropic aromatic copolyesters. It has been found that a number of Raman bands of thermotropic aromatic copolyesters show linear shifts towards lower wavenumbers with stress and strain following tensile deformation. The strain and stress dependencies of the 1600 cm−1 band due to stretching of the p-phenyl ring, have been studied in detail and discussed in relation to values reported for high-performance aromatic polymer fibres. The behaviour has been discussed in terms of the microstructure of the thermotropic aromatic copolyester materials compared with that of other highly-oriented aromatic polymer fibres.