Initiation viscosity effect

The most comprehensive simulation of a free radical polymerization process in a CSTR is that of Konopnicki and Kuester (15). For a mechanism which includes transfer to both monomer and solvent as well as termination by combination and disproportionation they examined the influence of non-isothermal operation, viscosity effects as well as induced sinuoidal and square-wave forcing functions on initiator feed and jacket temperature on the MWD of the polymer produced. 

Ultrasonic waves also bring about a reduction in the viscosity of nitrocellulose. The effect is more marked the higher the initial viscosity, and thus the longer the nitrocellulose chains (Sollner [93] Schmidt and Rommel [94]). For instance, nitrocellulose with a molecular weight of 123,000, estimated by means of Staudinger s viscosity equation, subjected in solution form to the action of ultrasonic waves suffered a degradation to a molecular weight of 70,000-80,000. 

Fig. 30. Relationship between intrinsic viscosity [q], and radiation dose (Ry Mrads.) finitial intrinsic viscosity. effective initial intrinsic viscosity after destruction of weak links, rgej radiation dose at gel point. Ratio of chain scissions to cross-links is 0.37 (87)...

At the comparison of concentration dependencies of the characteristic quantities (6.61) with experimental determinations, one has to remember that effect of excluded volume was not taken into account in equations (6.61), which allow us to say only about qualitative correspondence. The behaviour of the initial viscosity is the most widely studied (Poh and Ong 1984, Takahashi et al. 1985). The concentration dependence of the viscosity coefficient in the melt-like region can be represented by a power law (Phillies 1995). The index can be found to be approximately 25 + 1, in accordance with (6.61). There are some differences in the behaviour of polymer solutions, which are connected with different behaviour of macromolecular coils at dilution. 

Diluents are higher-MW components than solvents that are also added to the epoxy adhesive formulation to lower the viscosity and modify processing conditions. The primary function of a diluent in an epoxy resin formulation is to reduce its viscosity to make it easier to compound with fillers, to improve filler loading capacity, or to improve application properties. Solvents, certain curing agents, and flexibilized epoxy resins can also lower the viscosity of epoxy adhesive formulations, but this is not their primary function. The effect of various diluents on the initial viscosity of a diglycidyl ether of bisphenol A (DGEBA) epoxy resin is illustrated in Fig. 6.3. 

Dynamic solvent effect — is a phenomenon typical for adiabatic -> electron transfer and -> proton transfer reactions. This effect is responsible for a dependence of the reaction rate on solvent relaxation parameters. The initial search for a dynamic solvent effect (conventionally assumed to be a feature of reaction adiabatic-ity) consisted in checking the viscosity effect. However, this approach can lead to controversial conclusions because the viscosity cannot be varied without changing the -> permittivity, i.e. a dynamic solvent effect cannot be unambiguously separated from a -> static solvent effect [i]. Typically a slower solvent relaxation goes along with a higher permittivity, and the interplay of the two solvents effects can easily look as if either of them is weaker. The problems of theoretical treatment of the dynamic solvent effect of solvents having several relaxation times are considered in refs, [ii-iii]. 

Figure 2. Examining the cure chemorheology of HalChane 73-19 polyurethanes reveals the effect of temperature on initial viscosity, cold storage on shelf life, and side reactions on final cured properties.

Thin solid films of polymeric materials used in various microelectronic applications are usually commercially produced the spin coating deposition (SCD) process. This paper reports on a comprehensive theoretical study of the fundamental physical mechanisms of polymer thin film formation onto substrates by the SCD process. A mathematical model was used to predict the film thickness and film thickness uniformity as well as the effects of rheological properties, solvent evaporation, substrate surface topography and planarization phenomena. A theoretical expression is shown to provide a universal dimensionless correlation of dry film thickness data in terms of initial viscosity, angular speed, initial volume dispensed, time and two solvent evaporation parameters. 

The presence of NaCl has an important effect on initial viscosities. As seen in Figure 6 for Shell crude emulsions containing 3.0 and 4.0 x 10 moles NaOH/gram oil, the addition of NaCl first lowers the viscosities which go through minima and then rise with further addition of NaCl. At the optimum NaCl contents, viscosities were about 13% lower than the salt-free emulsions. 

Effects of Ironic Ions Fignre 5.22 shows the ferric ion (Fe ) effect on an HPAM viscosity at room temperatnre. The initial viscosity was 72.9 mPa s. We can see that when the Fe concentration was low, the viscosity loss was not... 

E, viscous activation energy initial viscosity Reaction and gel effects with no phase separation. k, constant... 

The effectiveness of a skimmer is rated according to the amount of oil that it recovers, as well as the amount of water picked up with the oil. Removing water from the recovered oil can be as difficult as the initial recovery. Effectiveness depends on a variety of factors including the type of oil spilled, the properties of the oil such as viscosity, the thickness of the slick, sea conditions, wind speed, ambient temperature, and the presence of ice or debris. 

Initial viscosity (Lo) Effect of mastication time and procedure of milling. Effect of peptisers... 

On the base of said above we suppose that presented formulation of polymerization rate with consideration of viscosity effect (equation 1) allows satisfactorily describing of initial stage of AG and MAG polymerization reaction at studied conditions. 

In the DHA-4VP studies, we found that copolymer yield and inherent viscosity varied considerably with the solvent used for polymerization (Table I). Solvents greatly affect free radical polymerization, although the mechanisms of some interactions is uncertain. For example, the effect of solvents on the rate of polymerization has been attributed to complex formation and to viscosity effects which alter rates of initiation, propagation, and termination (13, 14, 15). The data in Table I do not indicate any clear tendency, and no molecular weight-conversion correlation of the copolymers is apparent. The variation in copolymer yields is readily explained by differences in solubility of DHA. 

Tu et al. (1997) predicted NF flux by incorporating a gel-layer into the concentration polarisation model. Results corresponded well to filtration experiments with tannic acid. Gill %t al (1988) showed that viscosity effects in the boundary layer are more important than diffusivity. Concentration factors in UF of macromolecules were 40 to 400 times. A similar effect can be expected for large natural organic molecules. Kim et al (1992b) showed cake formation for low initial fluxes, and aggregation for high initial fluxes in protein UF. This demonstrated that solute-solute interactions in the boundary layer are important. 

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