FIBER STRUCTURE FORMATION IN HIGH SPEED MELT SPINNING OF POLY (ETHYLENETEREPHTHALATE)

EFFECT OF TAKE-UP VELOCITY ON UNIT CELL PARAMETERS AND SUPERSTRUCTURE OF FIBERS

Abstract

Fine structures of high speed spun PET filaments obtained at take-up velocity, 1000-9000m/min, were investigated by X-ray analysis. Crystalline density calculated from the measured unit cell parameters increased with increasing take-up velocity from 5000 to 700 m/min and then decreased slightly by further increase of take-up velocity. The crystalline density of 7000m/min filaments was calculated as 1.494g/cm³. Crystallite sizes and crystalline imperfection parameters were estimated from wide-angle X-ray diffraction. The crystallite sizes in the lateral directions as well as chain direction increased with spinning speed. In contrast, the imperfaction parameter along the chain axis decreased with take-up velocity. The crystallite sizes of as-spun filaments obtained at 8000m/min were 2 times larger in the chain direction and 1.5 times larger in the lateral directions than those of low speed spun, drawn and annealed fibers. Using the crystallite sizes obtained from wide-angle analysis, small-angle X-ray scattering diagrams were simulated according to the Tsvankin method. The super-structure of high speed spun filaments were estimated as follows. In the range of take-up velocity from 5000 to 6000m/min, the interface between crystalline and amorphous phase in the microfibril is highly inclined with respect to the plane perpendicular to the fiber axis, and in the range from 8000 to 9000m/min, this inclination is rather small, and many voids exists between the microfibrils.