Effect of the type of spinneret on the quality of polycaproamide fibres

Abstract

It was found that PCA fibres spun on spinnerets with a hyperboloid entry zone are characterized by lower density and higher birefringence. This improves the capacity of the fibres for orientational drawing and makes it possible to increase their physicomechanical indexes. The PCA textile fibres manufactured in the new spinnerets have good specific dyeing characteristics.Extrusion of a melt through spinneret openings is one of the most critical stages in spinning of polycaproamide (PCA) fibres [ 1 ]. The characteristics of this process are determined by the effect of a large number of parameters --the rheological indexes of the spinning medium, conditions of flow into the openings, size and geometric characteristics of the spinning capillaries, spinneret construction, etc. Industrial practice also shows that the stability of the spinning process and quality of the fibres obtained are determined to a great degree by the spinneret design and manufacturing quality.Conical-cylindrical openings have been the most common [2,3] due to the high technological effectiveness of their manufacture. However, practice shows that the existence of a dead zone in the corner of a channel can significantly alter the properties of the polymer (cross-linking, degradation, etc.) and the periodic change in the jet geometry causes marked inhomogeneity of the properties of the fibres [4].Spindbsenfabrik VEB (Grebzig, Germany) conducted special studies of the hydrodynamics of a polymer melt in the transition zone into a cylindrical channel and proposed a new spinneret design based on the results of these studies, where the entry zone is hyperboloid in shape [5,6]. According to their data, such shapes provide the most favorable hydrodynamic conditions in the capillary and eliminate eddy currents which can destabilize the spinning process. Regardless of this, there are no systematized data on technological substantiation of the spinneret design, and the information on this problem in the patent and technical literature is partial in nature. This situation led us to turn to studies to optimize spinneret design and to determine the effect of the conditions of flow in them on the properties of the fibres.PCA fibres are spun with high spinneret draws through spinnerets with openings of small diameter, causing sharp cooling of the polymer melt to a temperature close to the glass transition temperature. For this reason, no supermolecular structure recordable by optical methods develops in the fibres [7].We also know [8] that studying the structure of spun fibres is impeded by active cross-linking processes. This is primarily due to absorption of moisture from the oiling agent applied on the fibre and from the environment, which results in a change in the glass transition temperature and development of crystallization processes.We previously [9,10] tested the proposed .spinnerets and found no significant difference in spinning in experimental ( Fig. 1) and classic spinnerets. However, the fibres spun in both spinnerets differed in their capacity to ...

Structural changes in fabrication of vidlon polycaproamide textured twist thread

“…It was found in [9][10][11] that an oriented fibre has a laminar structure, and the outer layer exhibits high orientation of the macromolecules. The inside of the fibre is looser and has a spherulitic and fibrillar supermolecular structure.…”