Spinning and Quenching

In the normal polypropylene operation, one large spinneret is employed (may be two or three), with the number of spinneret orifices corresponding to the number of filaments 

After exiting the spinnerets, the filaments travel a short distance and enter a water-quench tank. Guides are arranged within the tank to ensure the filaments travel a proper distance for quenching. For a uniform product, the distance between the spinnerets and the water should be held constant. The water temperature should be maintained within close limits throughout the tank, and care should be taken to ensure the water contains no turbulent regions. 

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The orientation of the spun monofilaments and, consequently, the draw ratio necessary for producing a satisfactory product depend on the stretch rate during spinning and quenching, just as they do in the air-quench process. The larger the stretch rate, the higher the spin-line stress, the higher the orientation, and the lower the required draw ratio. 

Tensile Properties. Tensile properties of nylon-6 and nylon-6,6 yams shown in Table 1 are a function of polymer molecular weight, fiber spinning speed, quenching rate, and draw ratio. The degree of crystallinity and crystal and amorphous orientation obtained by modifying elements of the melt-spinning process have been related to the tenacity of nylon fiber (23,27). 

Figure 3.17. Three sequential variable-temperature X-ray scans (X = 1.797 A) performed on the same spin-coated KSb5S8 film after an initial heat and quench treatment. In each case, the heating rate is 1 °C/s and the sample is quenched to room temperature at the end of the heating portion of the cycle. White coloration in the plot corresponds to higher X-ray intensity.

The magnetic moments of the Ni clusters are dominated by the contribution from surface atoms.48,69 The analysis of Wan et al. indicates that the orbital and spin local moments of cluster atoms with atomic coordination 8 or larger are similar to those in the bulk (p spin 0.55 and orb 0.05 pB) 73 that is, the orbital moment is almost quenched for internal cluster atoms. In contrast, there is a large enhancement of the spin and orbital moments for atoms with coordination less than 8. This enhancement increases with the coordination deficit, and it is larger for the orbital moment. Wan et al.48 also analyzed the quantum confinement effect proposed by Fujima and Yamaguchi,56 i.e., the... 

Another class consists of extrusion immediately followed by an additional stage. This includes blow moulding, film blowing, quenched film forming, fibre spinning, and extrusion coating. 

The physical basis of the second type of approach rests upon the effect of the local electrostatic potential upon dynamic interactions at encounters with charged quenching molecules resulting in fluorescence (phosphorescence) (Vogel et al., 1986 Anni et al., 1994) or between a stable radical, e.g. nitroxide, and another charged paramagnetic species (Likhtenshtein et al., 1972 Likhtenshtein, 1976, 1988,1993). In such cases, the relaxation parameters, i.e. the life-time of the fluorescence (phosphorescence) chromophore or spin-spin and spin-lattice relaxation rates of paramagnetic species are dependent upon the frequency of encounters, and, therefore, on local electrostatic fields... 

There are no steric restrictions that militate against the formation of planar (CHjs. However, by the same principle that stabilizes benzene, (CH)5 should have an unpaired spin and residual angular momentum of h along z, because of the odd number of pxy- electrons. In order to quench the angular momentum one p2-electron could transfer to pxy and to pair the odd spin, the molecule may accept an extra electron. The most efficient solution would be accepting an electron with angular momentum, e.g. by photochemical electron transfer. This may account for the ease whereby (CH) sandwiches... 

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