Spinning speed

Flow processes iaside the spinneret are governed by shear viscosity and shear rate. PET is a non-Newtonian elastic fluid. Spinning filament tension and molecular orientation depend on polymer temperature and viscosity, spinneret capillary diameter and length, spin speed, rate of filament cooling, inertia, and air drag (69,70). These variables combine to attenuate the fiber and orient and sometimes crystallize the molecular chains (71). 

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). 

In the coupled process (Fig. 7c), the draw ratio, which affects the tenacity and elongation, lowers with increasing spinning speed. As draw ratio is increased, tenacity and initial modulus increase and elongation decreases. 

Fig. 10. Dependence of the production on spinning speed (89), where LOY is low orientation yam MOY, medium oriented yam POY, partially oriented...

Fig. 11. Effect of spinning speed on properties of nylon-6 fibers, where (T) is the tangent modulus (° ), the tenacity and (A ), the elongation. To convert...

At low rotation rates, less than the chemical shifts anisotropy, however, the powder spectra contained disturbing side bands dispersed among the isotropic chemical shifts. In order to discriminate between sidebands and isotropic resonances two spectra obtained at different spinning speeds were multiplied together or the differentiation was made by visual inspection. 

Fig. 11 (a) 2D NCO experiment with optimal control element inserted for 15N — 13C transfer. Transfer efficiencies for the ocNCO experiment optimized for 12 kHz spinning speed as function of (b) resonance offsets for 13C and 1SN and (c) rf inhomogeneity/adjustment in terms of scaling factors on the nominal rf field strengths for 13C and 15N. (d) Experimental ocNCO 2D spectrum of uniformly 13C,15N-labeled ubiquitin with the projections to the left comparing ocNCO experiment most intense) and DCP (less intense) based NCO experiments [reproduced with permission from [161] (a, d) and [164] (c)]... 

In the fast ( infinite ) spinning speed regime, a>R 3> < >n- (14) can be simplified by averaging over a rotor period ... 

Fig. 7 Comparison of the 170 DOR and MAS NMR (30 kHz) spectra of Ba2P207 (a), Mg2P207 (b), and Na4P2Oy (c) at B0 = 17.4 T. Spinning sidebands (asterisks, plus symbol) arise due to the limited spinning speed of the outer rotor ( 1,400 Hz). (Reproduced with permission from [146])...

If the sample is spun exactly at fjRL = 54.736° and at infinite spinning speed, the first-order term /, vanishes (33) and the second-order anisotropic term yields... 

If j Rf is exactly the magic angle and infinite spinning speed is assumed, the first-order anisotropic terms are zero for both single and DQ coherence (33). This does not hold true for finite spinning speed, but a complete averaging of the first-order effect occurs at the exact rotor cycles. Therefore, the x evolution time has to match exactly a multiple of the rotor period. The second-order anisotropy refocusing occurs for... 

Fig. 7 Identification of cubic ZB and hexagonal WZ polytypes of GaN by chemical shift (indicated) and NQCC differences based upon MAS-NMR of nuclei of both elements, (a) 71Ga MAS-NMR, with vertical expansions (red) showing ST reflecting NQCCs (reprinted from [60]). (b) 14N MAS-NMR at indicated spinning speeds, with measured T1 values (original spectra, data cited in [60])...

Fig. 11 63CuMAS-NMR at 9.0 kHz spinning speed, partial spectra of y-Cul (ZB structure) diluted in an inert matrix, showing broadening of first three STs as temperature is increased. The spectra shift to the right due to the temperature dependence of the chemical shift. Quantitative analysis of the broadening yields an activation energy for Cu+ hopping of 0.64 eV. Reprinted from [122]...

The theory behind this coating technique involves the equilibrium between the centrifugal forces created by the rapid spinning and the viscous forces determined by the viscosity of the liquid.1,88 Die film thickness can be varied by controlling the spin speed and time, as well as the viscosity of the solution. 

Empirically, it has been observed that the him thickness (t) is inversely proportional to the square root of the spin speed (co angular velocity).88... 

Figure 3.15. (a) Cross-sectional SEM of a spin-coated KSb5Se8 film, prepared using a 0.12M precursor solution (in hydrazine) with 5000rpm spin speed and deposited on silicon coated with -lOOnm of thermal SiOx. (b) Similarly prepared KSb5S8 film, subsequently heated to 475 °C for 2 min on a hot plate and cooled to room temperature. 

---