Spinning Preparation

Table 1.29. Comparison of CL-isothermal and oven tests on PP fibres with spin preparation...

After the harvest, the seeded cotton is ginned. The number of cleaning stages necessary depends on the condition of the raw cotton still containing the seeds. The cleaning is done with regular beaters, like those used by spinning preparation machinery. There are two kinds of machines the saw gin and the roller gin. 

Figure 3.2 schematically depicts a typical spinning preparation line (blow room) for cotton. It starts on the left with a bale breaker, followed by several cleaning units and a mixer, and is completed with a dust and foreign matter extractor. The next step is carding (not shown). 

The card is the first machine in the spinning preparation that delivers a sliver. The main tasks of the card are... 

Klein, W. (2008c), The Rieter Manual of Spinning," Vol 3 Spinning Preparation, Rieter Machine Works Ltd., Winterthur, Switzerland... 

Spectrogram 357 Spinning jenny 6 Spinning preparation 98 Spun-bonded nonwovens 207... 

In the usual preparatioii-evohition-detection paradigm, neither the preparation nor the detection depend on the details of the Hamiltonian, except hi special cases. Starthig from equilibrium, a hard pulse gives a density matrix that is just proportional to F. The detector picks up only the unweighted sum of the spin operators,... 

Polyimides for use ia molded products and high temperature films can be produced by the reaction of pyromelHtic dianhydride [89-32-7] and 4,4 -diaminodiphenyl ether [13174-32-8] ia DMAC to form a polyamide that can be converted iato a polyimide (13). DMAC can also be used as a spinning solvent for polyimides. AdditionaUy, polymers containing over 50% vinyHdene chloride are soluble up to 20% at elevated temperatures ia DMAC. Such solutions are useful ia preparing fibers (14). 

Acrylonitrile and its comonomers can be polymerized by any of the weU-known free-radical methods. Bulk polymerization is the most fundamental of these, but its commercial use is limited by its autocatalytic nature. Aqueous dispersion polymerization is the most common commercial method, whereas solution polymerization is used ia cases where the spinning dope can be prepared directly from the polymerization reaction product. Emulsion polymerization is used primarily for modacryhc compositions where a high level of a water-iasoluble monomer is used or where the monomer mixture is relatively slow reacting. 

HoUow fibers can be prepared from almost any spiunable material. The fiber can be spun directly as a membrane or as a substrate which is post-treated to achieve desired membrane characteristics. Analogous fibers have been spun in the textile industry and are employed for the production of high bulk, low density fabrics. The technology employed in the fabrication of synthetic fibers appUes also to the spinning of hoUow-fiber membranes from natural and synthetic polymers. 

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