Effect of spinning conditions on the structure of Vidlon polycaproamide textile fibres

Abstract

Combined thermal analysis showed that drawn polycaproamide fibres spun in spinnerets whose input zone is in the form of a hyperboloid are characterized by better thermal stability up to total melting in comparison to fibres spun in classic spinnerets. The lower weight loss and higher activation energy of thermal degradation of the fibres are evidence of this finding.In spinning of Vidlon polycaproamide (PCA) textile fibres, we tested [1] spinnerets from VEB Spind?senfabrik (Grobzig, Germany) where the entry zone is in the shape of a hyperboloid [2]. For comparison, we also used ordinary classic spinnerets [3,4]. In spinning on an EVP-2030 extruding machine using the experimental and classical spinnerets, no marked differences were found [5,6].Our other studies [7] showed that in spinning in severe temperature and pressure conditions, thermooxidative and thermomechanical degradation processes take place in polycaproamide. Mechanical degradation processes that result in breaking of some of the transfer chains in the macromolecules predominate under the effect of a temperature-force field. Thermooxidative and thermal mechanical degradation processes in the polymer determine the structure of the fibres and their behavior in drawing.We know from practice that spinning of PCA fibres at high spinneret draw values using spinnerets with small-diameter holes sharply cools the polymer melt to a temperature close to the glass transition temperature. For this reason, no supramolecular structure recordable by optical methods develops in the fibres [8].The study of the structure of as-spun fibres is complicated by actively occurring cross-linking processes [9]. This is primarily due to absorption of moisture from the oiling agent applied to the fibre and the environment, which changes the glass transition temperature and evolution of crystallization processes.Based on the premise in [10] that x-ray structural analysis is not suitable for studying the structure of spun fibres, we conducted the studies in a slightly different direction. We first determined the density and molecular orientation of the fibres. We found that the difference in the values of these characteristics of fibres spun in different spinnerets is so small that it is within the limits of error of the methods used. In our opinion, it is not possible to draw reliable conclusions based on these characteristics alone.We also found that fibres spun in different spinnerets have a different moisture sorption capacity and thus a different capacity for drawing. Fibres spun in the experimental spinnerets drew better. This finding led us to search for other methods of establishing the real difference in the structure of the fibres. In particular, the structural differences in PCA fibres can be judged by their thermophysical characteristics after drawing and heat treatment [11,12].The effect of the spinneret geometry on the structure of spun PCA textile fibres is examined here. For this purpose, PCA fibres spun in Spind?senfabrik spinnerets (samples A) and in classic spi...