Spinning techniques

The most common use of the polyamides is for the production of yams and fibres for different applications  

The polyamide chips are melted in special equipment at about 300 °C, and then sent through a heated pipe to the spiiming heads, where the melt spins produce the yam. Each yam is made up of a different number of filaments coming from the same spiimeret this gives the final product specific properties. 

The dimension of the yam is usually determined in deniers (weight in grams of 9000 metres of yam) lower deniers ( 100) usually characterise textile yams, higher deniers (up to some thousands) characterise BCF and technical yams. 

After being cooled with conditioned air, the yam undergoes different treatments in order to reach the required specifications  

The yam is normally wound up onto bobbins, but can be also cut and baled (staple fibres). 

The wet-spiminq method is used for polymers that decompose on 

In gel spinning, extrusion spinning, or gel-extrusion spinning, 35-55% solutions are used. The resulting filaments have a greater dimensional stability because of their lower solvent content, so that the rates of filament production can be greater ( 500 m/min). Polyfacrylonitrile) and poly(vinyl alcohol) are spun by this method. 

Dispersion spinning is a special spinning process for insoluble and nonmelting polymers. The dispersions of the polymers for spinning have other organic polymers added to increase their viscosity and to stabilize the fibers. This polymer is then burned off after the filaments have been 

In polymerization spinning, the monomer is polymerized together with initiators, fillers, pigments, and flame retardants, or other desired additives. The polymerizate is not isolated, but directly spun at rates of about 4000 m/min. The process is only suitable for rapidly polymerizing monomers. 

RAWAL and S. MUKHOPADHYAY, Indian Institute of Technology Delhi, India 

Key words extruder, filament, polymeric fluid, melt spinning, spinneret. 

Screen Adapter Breaker Spinning pack heater plate head 

In order to improve their structure and mechanical properties, the drawing of the filaments can further be carried out in a single- or two-stage process between take-up of the as-spun fiber and the final winding roller. Ideally, the filament formation in terms of spinnability requires the following conditions (Beyreuther and Brunig, 2007). 

In general, the spinnability of the polymeric melt is determined by the maximum possible DDR for a given polymer. As indicated above, steady-state conditions are a prerequisite for filament formation through the melt spinning route. These steady-state conditions are fundamentally dependent on the physical balance equations of mass, energy, and momentum as discussed below (Ziabicki, 1967 Beyreuther and Brunig, 2007). 

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The spinnerets in a production line assembly consist of multiple groupings of orifices thus the number of fibers from a single spinning ceU can vary. AU three spinning techniques mentioned above commonly employ spinning lines that carry as many as 250 fibers (sometimes referred to as a rope) drawn from a single multiorifice spinneret. 

A variation on the wet-spinning technique involves extruding into a heated gas environment. In this dry-spinning process, the temperature and composition of the gas control the extraction process. 

Improvements in melt spinning techniques and film filament processes have made polypropylene accessible for fiber production. Low-cost fibers made from polypropylene are replacing those made from sisal and jute. 

Spinning Tantalum can be formed by all conventional spinning techniques, provided a lubricant such as tallow is employed, and can be spun into configurations which cannot be produced by other forming methods. 

Reservoir or coaxial fibers can be produced from the glycolide/ lactide polymers (53,55). Two different methods have been investigated. Dunn (53) utilized a melt-spinning technique in which the drug was introduced during the spinning process as a suspension or solution in a suitable lumen fluid. Eenink (55) developed a dry-... 

CL produced in the presence of exogenous NADPH or NADH, which has been studied in Refs. [97,100], may originate from other sources than superoxide generation [90]. In our opinion [98], the data obtained on the basis lucigenin CL measurement, especially with the use of small lucigenin concentrations provide the reliable estimate of superoxide concentration while the use of ESR spin technique underestimates it, particularly in vascular tissue and cells (see Chapter 32). 

O 00 Freeze-in by ultrafast cooling Metals Melt splatting or spinning techniques... 

In order to study the cure behavior of the PTEB system, 1JC NMR of uncured and cured PTEB in the solid state was performed using crosspolarization magic-angle spinning techniques. The results show the polymerization to be via aromatization. The extent of cure versus cure temperature was determined quantitatively. It was found that the material was almost completely cured after one hour at 215°C. As the cure goes to completion, the ability to react decreases due to the corresponding rapid increase in Tg. Chemical shifts of the resonances in the cured material are consistent with a highly crosslinked condensed aromatic network. 

FIGURE 18.3 Fiber production using the three major spinning techniques. 

Table 9.5—NMR chemical shifts of the principal types of protons in organic molecules (reproduced by permission of Spectrometry Spin Techniques). 

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