Microvoids in fibers as studied by small‐angle scattering of x‐rays

Abstract Commercial and experimental fibers show diffuse small‐angle x‐ray scattering which varies in amount and shape, depending upon how the fibers were produced and also upon what aftertreatments they have received. Evidence is given showing that the amount of scattering should be interpreted in terms of the void content or microporosity in the fiber. These voids are too small to be seen by the light microscope, but are found to be measurable in the 15–200 A. range by present techniques. The spinning method greatly affects a fiber's void content. Wet‐spinning and dry‐spinning of a polymer solution produces fibers with a high void content. Melt‐spinning produces yarns with relatively low void content. The cause of this difference is discussed. Voids are shaped by the spinning process in almost all cases. The fiber can be visualized as having longitudinal cracks, crevices, or ellipsoidal. voids in the as‐spun condition, even though no molecular alignment is observed. This shaping was found to arise from a combination of ( 1 ) a shearing action of the spinneret and ( 2 ) tension on the windup. The voids are further elongated as the fiber is drawn.