Thread-line

In preparation of permselective hoUow-fiber membranes, morphology must be controUed to obtain desired mechanical and transport properties. Fiber fabrication is performed without a casting surface. Therefore, in the moving, unsupported thread line, the nascent hoUow-fiber membrane must estabUsh mechanical integrity in a very short time. 

Thorough washing of the fibres is mandatory to remove traces of acid which otherwise have adverse effects on the tenacity. It is usual for the thread line to be sprayed with a weakly alkaline solution before final washing in water and subsequent drying. 

The entity of the reversed spins in the crystal at h = h may be presented in the form of individual threads (lines), parallel to the external magnetic field and carrying an additional quantum of magnetic flux. 

In order to get certification according to OEKO-TEX Standard 100, aU components of a textile product have to conform to the required criteria without exception, meaning that in addition to the outer material also sewing threads, linings, prints, etc. as well as nontextile accessories such as buttons, zip fasteners, rivets, etc. have to comply with the requirements. The OEKO-TEX certificate is valid for a duration of 12 months. 

Melt fracture has been a very perplexing but fascinating problem ever since it was discovered. Another problem that seems to have the same degree of perplexity and fascination is draw resonance. Both are instabilities in polymer flows. (Draw resonance may also occur in Newtonian fluids.) Draw resonance is a periodic variation in the diameter of a spinning thread line above a critical drawdown ratio. Polypropylene and high-density polyethylene are both particularly susceptible to draw resonance. Petrie and Denn have presented a comprehensive review of the numerous theoretical and experimental studies of draw resonance conducted prior to 1976 [99]. 

The metering pumps are precision-made positive-displacement gear pumps, especially designed for melt spinning. They are used to ensure that a precise proportion of the melt from the extruder is delivered to each thread line and that the thread line denier does not vary with time. Modern pressure-feedback-controlled extenders operate remarkably steadily, but not steady enough for multifilament spinning without meter pumps. 

Guides Fittings of various shapes for controlling the path of a thread line. Tortora PG (ed) (1997) Fairchild s dictionary of textiles. Fairchild Books, New York. 

A similar technique can be employed when dry-spinning PHB from solution. In fact there is somewhat greater latitude in the drawing conditions for this process since the spherulitic morphology of solution-cast PHB is much finer and intrinsically more ductile than that of melt-cast polymer. Moreover, residual solvent in the thread line can act as a temporary plasticizer to aid the drawing process. 

The main difficulty with dry spinning PHB is in obtaining a sufficiently concentrated and viscous dope that can form a continuous fibre when pushed through a spinneret and maintain this stable condition despite the full weight of the thread line tending to draw it down prematurely into individual droplets. PHB homopolymer tends... 

A fiber can be defined as a material whose length is at least 100 times its diameter. Synthetic fibers are organic or inorganic materials that have been processed (spun) into the fiber form (thread lines). The synthetic fiber can be categorized as either staple (short) or continuous filament (very long). 

A simulation of the effects in melt spinning on crystallization is shown in Fig. 12-22, where temperature-time plots for crystallization are given for sheared, quiescent melts as well as for melt spinning itself. Changes in the crystallinity along the spinning fiber thread line are shown in Fig. 12-23 for high-density polyethylene. 

The thread lines are entangled with compressed air and then lubricated with special chemicals (spin finish) that give the yam the required physical properties. Some effluents and fumes are produced in this section and sent to a treatment facility. 

From there, the melted polymer is passed through spinnerets to produce thread lines. The thread lines are drawn, dressed with processing aids, and intermingled to give the yam its excellent mechanical properties. They are then wound up onto packages called cheeses . 

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