Viscosity retardation effect

TrialkylPhosphates. Triethyl phosphate [78-40-0] C H O P, is a colorless Hquid boiling at 209—218°C containing 17 wt % phosphoms. It may be manufactured from diethyl ether and phosphoms pentoxide via a metaphosphate intermediate (63,64). Triethyl phosphate has been used commercially as an additive for polyester laminates and in ceHulosics. In polyester resins, it functions as a viscosity depressant as weH as a flame retardant. The viscosity depressant effect of triethyl phosphate in polyester resins permits high loadings of alumina trihydrate, a fire-retardant smoke-suppressant filler (65,66). 

Additives. Because of their versatility, imparted via chemical modification, the appHcations of ethyleneimine encompass the entire additive sector. The addition of PEI to PVC plastisols increases the adhesion of the coatings by selective adsorption at the substrate surface (410). PEI derivatives are also used as adhesion promoters in paper coating (411). The adducts formed from fatty alcohol epoxides and PEI are used as dispersants and emulsifiers (412). They are able to control the viscosity of dispersions, and thus faciHtate transport in pipe systems (413). Eatty acid derivatives of PEI are even able to control the viscosity of pigment dispersions (414). The high nitrogen content of PEIs has a flame-retardant effect. This property is used, in combination with phosphoms compounds, for providing wood panels (415), ceUulose (416), or polymer blends (417,418) with a flame-retardant finish. 

An increase in viscosity usually accompanies competition. Water molecules bound by the hydrocolloid are no longer effective as solvent molecules and the concentration of the solution is thereby increased. Increase in viscosity itself has a retarding effect on crystal growth. 

An explanation for the form of the curve in Fig. 10.10 and also of those in Fig. 10.9 may be had by considering Nr to be decreased by using a series of fluids of increasing viscosity but keeping all other quantities the same. Starting with a low viscosity and a high NR, the coefficient is seen to be approximately constant. As NR decreases, a point is reached at which the viscosity is sufficient to retard effectively the flow of the film of fluid over the upstream face of the orifice plate and thus to reduce the contraction of the jet. Further increases in viscosity continue to reduce the contraction until finally the size of the jet is equal to that of the orifice. Thus, Cc continuously increases from its initial low value at high Nr until it equals 1.0. 

The concept of a retardation coefficient is associated with the idea of a uniform surface retardation, since in the absence of retardation the velocity distribution along the surface is also expressed by a sinusoidal relation. The considerations of surface viscosity in Boussinesq s theory and of the retarding effects of surfactants in Frumkin s theory result just in such angular dependence. Therefore, the discussion presented below can be carried out without predetermining the value of the retardation coefficient Xb ... 

The normal liquid chlorinated paraffins used as plasticizers for PVC have viscosities ranging from 100 to 40,000 MPa.s at 20°C. Products with chlorine contents ranging from 30 to 70% are on the market. Compatibility with PVC increases with increasing chlorine content but the plasticizing effect is reduced. The low viscosity products (chlorine content 30%—40%) are used as secondary plasticizers for PVC. They have a stabilizing effect on viscosity in plastisols. Chlorinated paraffins can be used up to a maximum of 25% of the total plasticizer content of the PVC plastisol without the risk of exudation. As chlorine-containing substances, these plasticizers also have a flame-retarding effect. 

Other effects are likely to influence emulsion viscosity, particularly high-intemal-phase-ratio emulsions in which the drops are separated by thin Aims. Both dynamic phenomena such as streaming potential or interfaciai viscosity retardation could take place at the drainage rate of these films. Electrical and steric repulsion, as well as surface hydration, are probably also important in these kinds of emulsions. These phenomena, that arc due to the pre.sence of ad.sorbed. surfactant onto approaching interfaces, have been studied in relation to stability problems but not for their effect on viscosity. However, it can be said as a rule of thumb that any effect that would tend to reduce the flow of inlerdrop film would result in increased viscosity or, rather, in impaired flowing ability. 

Although there has been extensive research (e.g., [1-9]) on the fire retardation effects of nanoclay on neat polymers, relatively few studies [15-31] have been conducted with polymer blend systems. In Table 8.1, the polymer blends as well as the tests conducted in [ 15-31 ] are presented. From this table, it is clear that the majority of these studies have been devoted to the morphology and thermal stability of polymer blend nanocomposites very few studies actually focused on their fire performance. Nonetheless, these studies [15-31] have generally led to the conclusion that the addition of nanoclay to polymer blends can result in remarkable improvement in (a) mechanical properties, (b) compatibilization, (c) viscosity, (d) thermal stability, and (e) flammability. 

Melamine cyanurate is used primarily in unfilled polyamides. Upon thermal decomposition, melamine is partially volatilized, whereas cyanuric acid catalyzes chain scission of polyamides. This leads to a decrease in melt viscosity and enhanced melt flow and dripping, which removes heat from the polymer and the polymer is extinguished. The vaporizing melamine probably prevents drips from flaming. The Are retardant effect of melamine cyanurate deteriorates significantly in glass-filled polyamides because glass fibers prevent free melt flow. ... 

The NO2 first must be absorbed by the water into the liquid film before it can react with the caustic. In such a liquid phase, two competing reactions take place NO2 with water and NO2 with NaOH. If the NaOH concentration in the liquid film is deficient, NO gas is released back into the gas phase in accordance with Equation 5-15. The diffusion rate of NaOH into the liquid film is a function of the liquid-phase solution concentration. For this system, 3 normal (12 wt%) NaOH seems to provide optimum absorption efficiency. Higher solution concentrations are less effective because the associated greater liquid viscosity retards the diffusion rate of the NaOH, as well as the products of reaction. 

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