Poly zero-shear viscosity

Linear phosphonitrilic chlorides (LPNCs), silicone fluids and, 22 573 Linear photodiode arrays, 19 153 Linear polyesters, 14 116 Linear polyethylene fibers, 20 398 Linear polyimides, synthesis of, 20 273 Linear polymers, 20 391 25 455 high molecular weight, 23 733 zero-shear viscosity of, 19 839 Linear poly(thioarylene)s, 23 705 Linear PPS, 23 704. See also... 

The zero-shear viscosity r 0 has been measured for isotropic solutions of various liquid-crystalline polymers over wide ranges of polymer concentration and molecular weight [70,128,132-139]. This quantity is convenient for studying the stiff-chain dynamics in concentrated solution, because its measurement is relatively easy and it is less sensitive to the molecular weight distribution (see below). Here we deal with four stiff-chain polymers well characterized molecu-larly schizophyllan (a triple-helical polysaccharide), xanthan (double-helical ionic polysaccharide), PBLG, and poly (p-phenylene terephthalamide) (PPTA Kevlar). The wormlike chain parameters of these polymers are listed in Tables... 

Getmanova and coworkers attached polar groups to the periphery of the hyperbranched poly(carbosilane) obtained from the polymerization of methyldiallylsilane (Scheme 25)78. This modified hyperbranched polymer possessed certain properties, such as zero shear viscosity, 7 g and surface tension, that were similar to comparably modified carbosilane dendrimers81. 

Figure 6.20 (a) Viscosity of solution of poly(y-benzyl-L-glutamate) (PBLG molecular weight 231,000), in m-cresol as a function of shear rate at 29 C for various mass percentages ranging from dilute ( 0.31%) to semidilute (0.31-2.5%) to concentrated isotropic (5-9.5%). The different symbols and lines refer to data taken on different instruments, (b) Zero-shear viscosity as a function of concentration, (reprinted with permission from Mead and Larson, Macromolecules 23 2524. Copyright 1990 American Chemical Society.)... 

Figure 7.10 The effect of poly-isobutylene (PIB) concentration on the zero-shear viscosity of the suspensions described in Fig. 7-9. The lines were calculated assuming / r,o(0) = K exp(—atTniin/A er), with values of the second virial coefficient A2 of 6 X 10 8 X 10 and 10 ". (From Buscall et al. 1993, with permission from the Journal of Rheology.)...

Ohshima, A., Kudo, H., Sato, T, and Teramoto, A., Entanglement effects in semiflexible polymer solutions 1. Zero-shear viscosity of poly(n-hexyl isocyanate) solutions. Macromolecules, 28, 6095-6099 (1995). 

According to Maerker and Sinton [197], lii r vis elastic behaviour of poly(vinyl alcohol)/borate gels is obtained at small drformation amplitudes only in that case the complex viscosity is five times as high as the zero sl r viscosity, whereas the complex viscosity measured at drformation amplitudes of 100% is equal to the zero shear viscosity. 

Laine, C. and Cassagnau, P. (2006) Prediction of zero-shear viscosity of poly (vinyl chloride) plastisols. Appl. Rhed.. 16 (2), 136-144. 

Fig. 5.5. Zero-shear viscosity qQ as a function of the temperature T for poly (acrylamide) (PAAm) and poly(A/-iso-propyl-acrylamide) (PipAAm) In aqueous solution (c=0.1 wt%).The viscosity for the solvent water as a function of the temperature Is plotted as well. Data from [77]...

The solvating envelope of the polymer chain can increase when the polymer-solvent interaction (solvent quality) increases with the temperature. The rising solvation of the chain leads to an expansion of the polymer coil and therefore to an increasing intrinsic viscosity. Figure 5.7 shows this increase of the intrinsic viscosity with the temperature for poly(acrylamide) in aqueous solution. The zero-shear viscosity of the same sample decreases with the temperature in Fig. 5.5. 

The viscosity is independent of the shear rate y at low shear rates as it can be clearly seen in Fig. 5.8. This viscosity is called the zero-shear viscosity /Jq. Above a critical shear rate Ycrit=80 s for the PAAm and Ycrit=5 s for the xanthan gum solution the viscosity decreases with the shear rate. Table 5.2 shows some examples for aqueous solutions of poly(acrylamide) of different molar masses and concentrations. The critical shear rate is generally shifted to lower values for higher molar masses. 

Figure 3.2 from Gupta et al. (2005) shows the combined zero-shear viscosity for seven poly(methyl methacrylate) (PMMA) samples ranging in Mw from 12,470 to 365,700 (g/mol) dissolved in dimethylformamide (DMF) illustrating this dependence. A change in file gradient of the plot occurs at a... 

Figure 10.5 shows a simulation of the poly(ethylene terephthalate) pilot plant experiments of George that were discussed in Section 7.4.4. PET is a difficult material to work with, and it has very small G and normal stresses. No uniform uniaxial extensional data are available. As noted in Chapter 7, Gregory has published extensive data on the zero-shear viscosity and relaxation time of PET, where the relaxation time is defined as the reciprocal of the shear rate at which non-Newtonian... 

Figure 4.1 The dependence of zero-shear viscosity /Jq on molecular weight for homopolymer melts (1) poly (dimethyl siloxane), (2) polyisobutylene,...

Using the analytical result (Eq. 8.37), they found that for mildly polydisperse systems, the zero-shear viscosity depended only on the weight average molecular weight as has often been reported, but that for broader distributions, the zero-shear viscosity varied with the poly-dispersity. They reported an approximate form of this dependency, valid when M IM > 1.5, which is shown here as Eq. 8.38. 

Zero-shear viscosity versus molecular weight for nearly monodisperse linear hydrogenated 1,4-poly butadienes at 190 °CThe lines showthe fits ofthedatatotheMilner-McLeish model... 

Figure 9.15 Zero-shear viscosity versus vol. fraction stars for bidisperse 1,4-poly butadiene star-linear blends as at 7= 25 "C.The symbols are for mixtures of a three-arm star of molecular weight 127,000 with linear polymers (M = 36,800) (M = 100,000) A(M = 68,000).The curves are the predictions of the theory of Milner etal. [23] using a = 4/3. The solid lines are for predictions with disentanglement relaxation and the dashed lines are without disentanglement relaxation.The data are from Struglinski etal. [35].The parameter values are the same as in Fig. 9.6. From Park and Larson [27].

FIGURE 11.7 Comparison of zero-shear viscosity and molecular weight for various PLA materials, squares PLLA at 180 °C open circles Poly(85%L-co-15% D-lactide) at 100 °C filled circles Poly(85%L-co-15% D-lactide) at 85 °C. (Reprinted with permission of the publisher from Lim et al., 2008.)... 

Effect of molecular weight on zero-shear viscosity and elasticity coefficient for poly(L-lactic acid) (PLLA) at 200 >C (Cooper-White and Mackay, 1999). 

Fig. 5.4. Ratio of Maxwell-constant to intrinsic viscosity as a function of molecular weight for linear oligomers of poly oxy-propylene glycol in cyclo-hexanol at 20° C (full circles). Ratio of birefringence to shear stress in the limit of zero shear stress for the same oligomers in bulk (temperatures 20—60° C) (open squares). The experimental point at the righthand side is obtained on a high molecular weight sample, Tsvetkov, Garmonova and Stankevich (166)...

A broad molecular-weight distribution (MWD) typically increases the shear and pressure sensitivity of polymer melts. However, the effect of MWD on zero shear-rate viscosity varies a broad MWD increases the zero shear-rate viscosity of polyethylene and HIPS, but decreases t o for ABS and poly(vinyl chloride). The effect of MWD on temperature sensitivity also seems polymer-dependent. 

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