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New methods of bulk and surface modification of polypropylene filaments at the stage of their forming from a melt are presented. Modification of polypropylene filaments by introducing a small amount of stabilized metal-containing nanoparticles into the fiber-forming polymer during the melt generation step is considered. It was found that the modified filaments exhibits high quality characteristics. A method for surface modification based on applying a suspension of finely dispersed polytetrafluoroethylene to the surface of a semi-cured polypropylene filament during the sizing stage is also considered. The modified filament acquires an extremely high chemical resistance and a very low coefficient of friction. [ABSTRACT FROM AUTHOR]

The influence of the spinneret draw ratio and subsequent solid-state stretching of polypropylene multifilament yarns (PMY) on changes in the orientation of crystallites and molecular chains in the polymer amorphous regions was studied using x-ray structure analysis. It was shown that crystallites and molecular chains of amorphous polypropylene (PP) became significantly more oriented already for a yarn spinneret draw ratio of 2400% and changed little if it was increased further. Additional solid-state stretching of yarns at elevated temperature had practically no effect on the orientation of PP crystallites but did halve the misorientation angle of molecular chains in the polymer amorphous regions. This phenomenon suggested that the substantial decrease of the elongation at break and increase of PMY physicomechanical parameters could be attributed to distribution of the applied load onto a larger number of continuous chains. [ABSTRACT FROM AUTHOR]

The method of statistical modeling is used to determine the relationship between the thickness of filaments and the coefficients of variation for time and density. It is shown that the standard deviation of the outgoing flow is directly proportional to these coefficients individually and in combination. The mathematical model which was constructed allows these relationships to be used to design new systems for controlling the passage of a polymer solution through a spinneret. [ABSTRACT FROM AUTHOR]

We have studied the basic characteristics of spinneretless electrospinning of polyacrylonitrile fibers. We show the effect of the viscosity and the type of solvent on the fiber drawability of the solutions. [ABSTRACT FROM AUTHOR]

We present comparative results of tests on commercial and experimental platinum/palladium spinnerets in forming polyacrylonitrile filament yarn of 50 tex. The experimental spinnerets were made with holes of high precision diameter (0.08 ± 0.001 mm). The spinnerets were characterized by their integrated throughput (the flow-through time for distilled water) while the filament yarns were characterized by their linear density. We demonstrate a correlation between the filament linear density and the flow-through time. In this case, the criteria for uniformity of the filament with respect to linear density (variance, range, mean-square deviation, coefficient of variation) are statistically significantly smaller for the experimental spinnerets than for the commercial spinnerets. [ABSTRACT FROM AUTHOR]

A calculation scheme is proposed which allows establishing the effect of creep on the sag of the spinneret plate in a spinneret feeder and its lifetime. The sag increases and the feeder lifetime decreases with an increase in the stresses arising when the plate is loaded. [ABSTRACT FROM AUTHOR]

The scientific principles of direct dissolution of cellulose in the NMMO—water system demonstrate the major possibility of obtaining concentrated spinning solutions and spinning hydrated cellulose fibres from them. The specific features of the properties of NMMO (high boiling point and insufficient thermal stability) that dissolves the NMMO—water system (narrow concentration range, optimum for dissolution of cellulose) makes it necessary to recycle the washing water by evaporating it, which causes high power consumption for this process. It is expedient to examine the possibilities of membrane technologies, including electrodialysis, for solving problems of recycling the solvent and cutting power consumption. However, this path only allows partially concentrating used washing water, since there is the danger of crystallization of NMMO di-and monohydrate. Spinning through an air gap from highly viscous solutions with long relaxation times at high spinneret draw ratios results in highly oriented fibres with high tensile rigidity (high deformation modulus). Fabrication of fibres whose properties correspond to ordinary viscose fibres will perhaps require “going away” from highly viscous solutions to a lower concentration and spinning by the ordinary wet method, but the volume of solvent used increases significantly, recycling it is more difficult, and power consumption increases. For the same reason of high orientation, the fibres exhibit important fibrillation when wet, and a “peach skin” effect is formed in the finished textiles. To reduce fibrillation, special treatments of the fabrics must be used, biofinishing, for example. During use of the articles, fibrillation can reappear, in laundering, for example. The technology for fabricating fibres of the Lyocell type requires solving many problems. Developing research on selecting alternative solvents and dissolving systems for direct dissolution of cellulose to obtain concentrated spinning solutions is simultaneously useful. [ABSTRACT FROM AUTHOR]

To obtain stable spinning of glass and basalt fibres, it is necessary to significantly increase the angle of wetting of the bottom of the spinneret feeder by the spinning melt at the time the fibre is loaded. To increase the angle of wetting in loading the fibre, more intensive cooling in the zone under the spinneret can be used. [ABSTRACT FROM AUTHOR]

By modeling the movement of viscose rayon through a spinneret by the finite element method, we establish the dependence of the filament quality on the stability of a number of factors. We demonstrate the relationship of the boundary temperature gradients and the shape of the heat flux distribution in the solution. The mathematical model developed allows us to use the identified relationships in synthesis of control systems. [ABSTRACT FROM AUTHOR]

Experimental data supporting the feasibility of application of Poiseuille equation for determining the dimensions of the inner spinneret channel and the height of the hydrostatic melt column above the spinneret plate are reported. These data can be used to develop a method for calculating the strength and rigidity of the key components of the spinneret feeders. [ABSTRACT FROM AUTHOR]