A novel video opto-mechanical (VOM) device for studying the effect of stretching speed on the optical and structural properties of fibers

Using a novel video opto-mechanical (VOM) device, the effect of stretching speed on the optical and structural properties of polypropylene (PP) fibers during the dynamic stretching process is studied. The objective of the present study is to correlate the optical and mechanical properties of PP fibers with the speed of stretching using the multiple-beam Fizeau fringes system. The skeletonization of the multiple-beam Fizeau fringes are determined automatically by using one-dimension Fourier transform method. The stepper motor is adjusted in order to stretch the fibers continuously with constant and uniform speed until breaking of the fiber. The refractive indices, birefringence, transverse sectional area and the orientation function of PP fibers are studied as a function of the draw ratio at different speeds of stretching. An empirical formula is given to correlate the birefringence of PP fiber and both the draw ratio and the speed of stretching. Stretching process of PP with low speed (slow stretching) is recommended to overcome the necking deformation along the fiber. The VOM device could be used to measure the yield strain. The draw ratio-stretching speed superposition is discussed with some details. Microinterferograms are given for illustration.