THE USE OF INFRARED-SPECTROSCOPY TECHNIQUE FOR THE STRUCTURAL CHARACTERIZATION OF ISOTACTIC POLYPROPYLENE FIBRES

Isotactic polypropylene (iPP) fibres were produced by melt spinning method with take-up speeds between 2500 m/min and 4250 m/min. The effect of production parameters on structural parameters such as crystallinity and tacticity is investigated using infra-red spectroscopy together with density measurements. Samples were also characterized using Melt Flow Index (MFI) measurements. Curve fitting of IR spectra yielded accurate peak parameters which are in turn used in the evaluation of tacticity and fractional crystallinity values. Evaluation of isotacticity and atacticity fractions were performed using the absorbance ratios of the IR bands at 998, 841 and 973 cm-1 (A998/A973, A841/A973). Isotacticity fractions evaluated from A841/A973 are generally found to be higher than that evaluated from the ratio of A998/A973. Isotacticity fractions show an increasing trend after about the extrusion speed of 3000 m/min whereas atacticity fractions decrease accordingly. Crystallinity fractions obtained from density and infra-red spectroscopy methods are compared. In general, crystallinity fractions obtained from IR-spectroscopy are found to be slightly higher than the density based crystallinity fractions.