4.0 Spinning University of Massachusetts （4.0旋转马萨诸塞大学）.pdfVIP

Tuesday, February 16, 1999 Fiber Spinning Page: 1 4.0 Spinning 4.1 Melt Spinning 4.2 Dry Spinning 4.3 Wet Spinning As mentioned previously, fibers are formed by the extrusion of the polymer melt or spin dope through tiny holes in a spinneret plate. Such a plate may contain 1,000 holes or more. Textile fibers are relatively fine, so the diameter of the hole may be only a few mils, where one mil is 0.001 inches (25.4 µm). The thickness of the filament is generally not given in linear dimensions, but rather in terms of mass per length. For some reason the fiber industry has adopted the terms denier and denier per filament, dpf, to express the filament size. One dpf corresponds to a mass of 1 g in a length of 9000 meters! If the density of the polymer is 1 g/cm3, this would correspond to a diameter of 1.2 x 10-3 cm, or about half a mil. Typically, textile fibers are in the range of 3 to 15 dpf. Recall that one g is roughly 1/30 of an ounce. In melt spinning, the filaments are normally drawn down, or stretched, just downstream of the spinneret holes. The stretch is of the order of 2 to 3x, so the spinneret hole may be 50 to 75% larger than the filament diameter when it is first cooled. Additional post formation stretching may also be used, however, so that the final filament diameter may be one-half or less than the diameter of the spinneret hole. The spinneret hole is usually only slightly longer than its width, in part to minimize pressure drop at the plate. But the plate still has to be strong enough to withstand the upstream pressure. For this reason, the melt passes through a conical section before reaching the final spinneret hole, so that the plate can be relative thick (see slide)