Abstract
The relation between the draw resonance and filament irregularity in the melt spinning of polypropylene was studied. The derivation of equation between draw resonance and filament irregularity, approximation of the equation and its limiting values were made and the experimental verification of the theory and its simplification, and the shape of the fiber diameler variation caused by draw resonance were investigated. A photo-sensor was used for on-line measurements of the fiber diameter variations in the melt spinning process and the period of draw resonance was obtained by courier transfermation. By the use of courier series, a series equation expressing the irregularity CV(%) in terms of Fourier coefficients and Dmax/Dmin value, was derived. After comparing the actual CV(%) with the calculated CV(%) at various Fourier integer n values, it was found that the equation could be simplified by omitting courier coefficient subscript values neater than 6. The effect of spinning variables on the filament irregularity of polypropylene monofilaments were investigated by carrying out the melt spinning at both isothermal and nonisothermal conditions. The results showed that the filament irregularity CV(%) increased with the Dmax/Dmin values. The filament irregularity increased with the draw ratio at both isothermal and nonisothermal conditions, and the shape of fiber diameter variation was changed from quasi-sinusoidal waveform to a pulse train. Draw resonance was affiected by spinning conditions, but at the fixed draw resonance values the constant irregularity is obtained, independent of the spinning conditions. The fiber diameter variation showed a transition from quasi-sinu-soidal waveform to a pulse train at a Dmax/Dmin value of approximately 3. From the analysis of frequency spectrum obtained from courier transformation, the contribution of the 2nd and 3rd resonant frequency to the total fiber diameter variation increased with the draw ratio.