Raman spectroscopy of Kevlar fibres during deformation— Caveat emptor

It has been demonstrated that when aromatic polyamide fibres such as Kevlar 49 are subjected to mechanical deformation, significant frequency shifts are obtained for the peak position of the 1610 cm −1 Raman band using both 632·8 nm and 488 nm laser radiation. Two earlier reports of the deformation of fibres in a 488 nm argon ion laser beam reported no such frequency shifts. It has been shown that this wavelength of laser light can degrade Kevlar fibres. This causes premature failure of the fibres through chain scission and the fibres break at low strains before significant levels of stress or strain can be achieved. Hence, the previous conflicts can be resolved and it has been demonstrated that simultaneous Raman spectroscopy and mechanical deformation is a powerful method of following the micromechanics of fibre deformation.