Spin stretch factor

Spin stretch factor Tex per filament Tenacity Elongation (%) Initial modulus Orientation angle... 

The spinning speed is 800 m min, and the filaments are thus accelerated in the spin-line by a factor of 800/8.87 = 90. In practice this is viscous flow rather than molecular orientation. Calling this a draw ratio is misleading draft , drawdown or spin stretch factor are better notions. 

Example No. Resin Melt Flow Rate (g/lOmin) Spinning Temp., Die Diameter, mm Die Land Length, mm Shear Rate, sec Wind-up (Draw) Speed, m/min Spin Stretch Factor... 

The latter figure shows the mechanical properties, measured at room temperature, of as-spun poly(l,4-phenylene terephthalamide) fibers plotted against the polymer concentration of the solutions from which the fibers were produced. The draw-down ratio, or spin-stretch factor (wind-up speed/ extrusion rate) was adjusted for each concentration to maintain a constant fiber diameter. Remarkably, these reported results display no discontinuity in the fiber tensile strength or stiffness at the onset of the formation of the anisotropic phase. 

As in the case of the aromatic polyamides minimum values of >/i h for the production of good fibres are quoted and the useful number average molecular weight range for the polymers based on VIII and IX is said to be 50000-100000. Spin stretch appears to be a factor in the development of the as-spun properties. ... 

A fluorescence decay of the ensemble of many CV molecules on a PMMA film is shown in Fig. 12. The decay was not fitted to a single exponential function and a stretched exponential function, but was well fitted to a biexponential function I(t) = Af exp(-t/xf) + Asexp(—t/ts), where tf and ts are time constants and Af and As are pre-exponential factors. We obtained tf = 0.43 ns and ts = 1.76 ns, and the ratio As/Af = 1.14. Compared with the excited state lifetime of CV (2-3 ps) in methanol and ethanol [5-8,58-68], the fluorescence lifetime of CV on a PMMA film increased more than two orders of magnitude [9-12] thus, so did the fluorescence quantum efficiency. The enhancement of the fluorescence efficiency of CV on a PMMA film made it possible to observe single CV molecules. Figure 13 shows fluorescent spots on a PMMA film on which a drop of 1-nM CV in methanol was spin-coated. The number of fluorescent spots in an image linearly increased with increasing concentration of a CV methanol... 

The factors in determining the barriers to ring-inversion in the spin paired and odd-electron molecules are proposed to be different bond lengths and angles associated with the oxygen atoms, related stretching and bending force constants, tor-... 

The structure of a molecule that one observes will depend on the timescale of the experiment relative to the dynamics of the molecule. Crystallography yields the space-averaged structure. One obtains information regarding the average position of the atoms, the dynamics are swallowed up in the temperature factors. The calculation proceeds by first identifying the dominant vibrational mode(s) involved in the coupling. For d and high-spin d" complexes, this is the U2(ML6) asymmetric skeletal stretch depicted in Fig 7 below ... 

Table 9 records the calculated vibrational frequencies of the triplet aniline and scaled with appropriate factors. The v(C—N) stretch frequency is predicted at 1252 cm-1, which is marginally smaller than that of 1293 cnr1 of ANI ground state. However, the corresponding IR intensity is much reduced in the high spin state. The vibronic structure of phosphorescence bands was analyzed, but they are puzzling, very different from those obtained under other experimental conditions. However, the presence of b modes is always observed149. 

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