Effect of Molecular Weight on Viscosity

Figure 2.4. Effect of molecular weight on viscosity of adipates at 20°C.

As with resoles, the central issue in design of novolacs is molecular weight. The effects of formaldehyde-to-phenol molar ratio and formaldehyde conversion on molecular weight of novolacs has been well studied and reported [192,193]. The effects of molecular weight on most of the important properties are also available [193]. These include Tg, melt viscosity, gel time, hot-plate flow, glass-plate flow. 

Recently, we explored the effect of molecular weight on the pattern and employed post-dewetting processes to alter the shape of the dewetted polymer droplets. Since the viscosity of a polymer solution is nonlinear with respect to concentration and also strongly dependent on polymer weight, we expected a drastic effect. Figure 11.4... 

Godunov SK, Romenskii El (1972) Non-steady state equation of non-linear theory of elasticity in Euler co-ordinates. Zh Prikl Mech Technich Phys 6 124-144 (in Russian) Golovicheva IE, Sinovich SA, Pyshnograi GV (2000) Effect of molecular weight on shear and elongational viscosity of linear polymers. Prikl Mech Tekhnich Fiz 41(2) 154-160 (in Russian)... 

Figure 2. Effect of molecular weight on reduced bulk viscosity expressed as a master curve for fractionally precipitated samples of (BAB)X which contain 50 wt % polystyrene and MA = 13,500. T = 463°K.

Figure 4. Effect of molecular weight on the concentration dependence of vis-cosity at 1.3 s K Solvent is 2.0 wt % NaCl. Hydrophobe monomer is 1.0 mol % N-n-octylacrylamide. Hydrolysis level is 18 mol %. Intrinsic viscosity (dL/g) , 2.0 u, 7.6 x, 8.4.

Figure 8, Effect of molecular weight on current noise spectra for aqueous solutions of PEO having approximately ual apparent viscosity at a shear rate of 250 sec. (top] 1 % PEO, Mw 4 (middle) 43%, 6 10 (bottom) 6%, 10 - Direct current, 20 fxA ...

The absorption spectra of polyaniline films cast from sulfuric acid are strongly dependent on the molecular weight (viscosity). Figure 2 shows spectra of three thin films spin-cast from sulfuric acid solution, and subsequently treated by 0.5M HCl solution to achieve full protonation. To study the effect of molecular weight on the absorption spectrum, we used emeraldine base samples fractionated from the same preparation batch (polymerization and compensation) as described in the previous section. This procedure prevents any uncertainty in the viscosity value, and avoids slight variations in the preparation procedure. 

The molecular weight and molecular weight distribution affect many of the physical properties of PVA. These include solution viscosity, tensile strength, block resistance, water and solvent resistance, adhesive strength, and dispersing power. These effects are well documented (1,9-11). Reliable and accurate methods are required to understand the effect of molecular weight on physical properties and, ultimately, the performance of PVA in any application or process. 

Figure 8.9 The effect of molecular weight on the zero shear viscosity (ZSV) of Thermx LNOOl [5]. 

FIGURE 3.6 Effect of molecular weight on the viscosity of PVAC solutions. PVAC polymers (Cairn) (Table 7.1) were dissolved in cyclohexanone to form 40% solutions (by weight). These were dyed to aid visibility. The test tubes were tipped over and photographed after 2seconds. The low-molecular-weight polymer solutions flowed faster (a) S2. (b) SI. (c) S27. 

The empirical equation relating viscosity at zero-shear rate (t]o) to molecular weight for linear amorphous polymers is used to compare PLLA melts with those of conventional polymers. The form of this equation has been applied to the elasticity coefficient, Aq, to further quantify the effect of molecular weight on the elasticity (Cooper-White and Mackay 1999) ... 

Figure 6.4 Effect of molecular weight on zero-shear viscosity and elasticity coefficient for PLLA at 200°C (Ferry 1980).

Flory, R, Kinetics of polyesterification A study of the effects of molecular weight and viscosity on reaction rate,/. Am. Chem. Soc., 61,3334-3340,1939. 

Effect of Molecular Weight on the Zero-Shear Viscosity of Disordered Diblock Copolymers... 

The effect of molecular weight on the solution viscosity of a surface coating determines the non-volatile (solids) content of the surface coating. As the molecular weight increases, additional solvent will be required, to maintain the viscosity at a level suitable for application. This is illustrated in Figure 1-61. 

Figure 2.3. Effects of molecular weight on the property of synthetic fibers and the viscosity of polymer melt or solution.

Equations 8.48 and 49 show the effect of molecular weight on the zero-shear viscosity. The formation of polymer fibers is carried out at high shear rates. Figure 8.19 shows the viscosity-molecular weight relationships at different shear rates. It is seen that at, the shear rate does not affect the viscosity-mo-... 

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