On Line study of optical and structural behaviour of annealed as spun isotactic polypropylene fibres under creep Deformation

Double-arm of multiple- beam Fizeau system in transmission, attached with a modified creep device was used to investigate the opto-viscoelastic properties of isotactic polypropylene (iPP) fibres under different annealing conditions. The mean refractive index, birefringence, orientation, density and crystallinity were calculated for the annealed iPP fibres during creep deformation. Crystallinity behaviour was investigated during creep experiments at different annealing conditions which indicated a remarkable improvement in the properties of the investigated samples. The creep compliance curves were obtained at three different values of stresses for different annealing temperatures and different times of annealing. An empirical formula was suggested to describe the creep compliance curve of annealed iPP fibre and the constants of this formula were determined from the fitting parameters of the obtained creep curves. Kelvin chain was used to model the mechanical behaviour of iPP fibre under creep process. Illustrations using graphs and microinterferogrames are shown.