Polyvinyl acetal viscosity

Polymer Type Polyvinyl Acetate Viscosity (cps) 1000-1400 Solids (% min) 55 pH 4.5-6... 

Bead Polymerization Bulk reaction proceeds in independent droplets of 10 to 1,000 [Lm diameter suspended in water or other medium and insulated from each other by some colloid. A typical suspending agent is polyvinyl alcohol dissolved in water. The polymerization can be done to high conversion. Temperature control is easy because of the moderating thermal effect of the water and its low viscosity. The suspensions sometimes are unstable and agitation may be critical. Only batch reaciors appear to be in industrial use polyvinyl acetate in methanol, copolymers of acrylates and methacrylates, polyacrylonitrile in aqueous ZnCh solution, and others. Bead polymerization of styrene takes 8 to 12 h. 

Polyvinyl Acetate. Two polyvinyl acetate samples (PVAc 1 and PVAc 3) also were analyzed. Both samples have been shown to be branched by Hamlelec (50) by a SEC/LALLS study. Table 8 shows the results obtained from SEC/Vlscometry along with some of the available data. It is seen that the intrinsic viscosity values for... 

Tager and co-workers (51) have invoked bundle structures to explain correlations between the viscosities of concentrated polymer solutions and the thermodynamic interactions between polymer and solvent. They note, for example, that solutions of polystyrene in decalin (a poor solvent) have higher viscosities than in ethyl benzene (a good solvent) at the same concentration, and quote a number of other examples. Such results are attributed to the ability of good solvents to break up the bundle structure the bundles presumably persist in poor solvents and give rise to a higher viscosity. It seems possible that such behavior could also be explained, at least in part, by the effects of solvent on free volume (see Section 5). Berry and Fox have found, for example, that concentrated solution data on polyvinyl acetate in solvents erf quite different thermodynamic interaction could be reduced satisfactorily by free volume considerations alone (16). Differences due to solvent which remain after correction for free volume... 

Fig. 8.13. Dimensionless shear rate /30 locating the onset of shear rate dependence in the viscosity in narrow distribution systems of linear polymers vs cM/qM. Symbols for data on additional polymers are A for undiluted 1,4 polybutadiene (322), for undiluted poly(dimethyl siloxane) (323), and O for solutions of polyvinyl acetate in diethyl phthalate (195). The dotted lines indicate the ranges of for the intrinsic viscosity...

Fig. 19. Viscosity (log n in Pa s) as a function of temperature for polymethacrylate (a) and polyvinyl acetate according to Eq. (44) (statistical theory, this work)...

Wagner, R. H. Intrinsic viscosities and molecular weights of polyvinyl acetates. J. Polymer Sci. 2, 21 (1947). 

The following Table 2.4 lists the components of the basic formulation that were successful in dissolving polyvinyl acetate and polybutyral in ethanol with an adjusted viscosity for proper application to tissue. 

Recent investigations have shown that the behavior and interactions of surfactants in a polyvinyl acetate latex are quite different and complex compared to that in a polystyrene latex (1, 2). Surfactant adsorption at the fairly polar vinyl acetate latex surface is generally weak (3,4) and at times shows a complex adsorption isotherm (2). Earlier work (5,6) has also shown that anionic surfactants adsorb on polyvinyl acetate, then slowly penetrate into the particle leading to the formation of a poly-electroyte type solubilized polymer-surfactant complex. Such a solubilization process is generally accompanied by an increase in viscosity. The first objective of this work is to better under-stand the effects of type and structure of surfactants on the solubilization phenomena in vinyl acetate and vinyl acetate-butyl acrylate copolymer latexes. 

It is well known (3,5,6) that sodium lauryl sulfate interacts with some polymers such as polyvinyl acetate causing solubilization of the insoluble polymer leading to an increase in viscosity. In Figure 3, viscosity of the homopolymer and 70/30 VA/BA at various NaLS/polymer ratio is shown. It is seen that the viscosity of the 2% latex dispersion increases with increase in NaLS/polymer ratio. Similar visoosity data for the 85/15 VA/BA was intermediate between the homopolymer and 70/30 VA/BA latexes. Surfactants that showed a normal saturation type adsorption behavior did not show any significant visoosity increase of the latex. 

Since the derivation of Eq. (40) tacitly assumes that solutions are sufficiently concentrated with respect to polymer, the viscosity data to be compared with it must refer to such systems, preferably including the pure polymer. Unfortunately, such data are available only for a limited number of polymer-diluent pairs in which polymers are exclusively of amorphous type, and we have to leave thorough testing of the theory for future work. Recent tests made with data on polystyrene, polyvinyl acetate, and polymethyl methacrylate [Fujita and Kishimoto (1961)] have indicated that Eq. (40) was obeyed fairly well except at relatively high diluent concentrations where the plots generally exhibited a downward curvature. The derived curves for f(0,T) vs. T approximately consisted of two straight lines intersecting at T near T° of the respective polymers. For polystyrene and polyvinyl acetate the slopes of these lines ior T>T°g were quite close to, but for polymethyl methacrylate it was much less than, the WLF value of a,. Furthermore, the f(0,T) curves deduced for polystyrene were essentially independent of the kind of diluent, as expected from the theory described above. 

M 6 Matsumoto, M., and Y. Ohyanygi Viscosity-molecular weigbt relationship for polyvinyl acetate. J. Polymer Sci. 46, 441 (1960). 

Plot the reduced viscosity of each solution against concentration, and extrapolate to zero concentration to obtain the intrinsic viscosity, [t ]. Finally, calculate the molecular weight of the polyvinyl acetate by the formula... 

In general, these groups of cellulose ethers have been used for their innate adhesive properties and to provide thickening to adhesive formulations. They are used for plywood adhesives, industrial adhesives, wallpaper paste, library paste, and latex adhesives. For example, methylcellulose is used in some adhesives as an additive to control viscosity, especially in the heat-cure phenol-formaldehyde glues and other hot-pressing adhesives. Hydroxyethylcellulose is used as an ingredient in polyvinyl acetate emulsions, where it acts as a thickener and protective colloid. 

Cellulose ethers have also been used in the ceramic industry (7). Since their appearance in 1959, water-based cellulose ethers have replaced solvent-based adhesives. The adhesives used for ceramic tile are ready-mixed products based on natural or synthetic rubber, polyvinyl acetate, and other resins, and they all contain cellulose ethers of one kind or another (e.g. MC, EC, HPMC, HEMC, HEC). These cellulose ethers reduce water loss, modify the viscosity of the mix, and can provide excellent adhesion for dry, very porous tiles. 

Kishimoto, a. Diffusion and viscosity of polyvinyl acetate-diluent systems. J. Polymer Sci. 2A, 1421 (1964). 

Viscosity (dynamic) the viscosity of a solution of polyvinyl acetate phthalate methanol (1 1) is 5000 mPas. In metha-nol/dichloromethane systems, viscosity increases as the concentration of methanol in the system increases. 

Solution—polymerization of monomers dissolved in solvents in which the polymer products are also soluble Lower viscosity than bulk and better heat transfer and mixing direct application of solution less reactor fouling Smaller reactor capacity than bulk high separation cost often inflammable and toxic solvents lower molecular weights SBR, polyvinyl acetate, polystyrene, acrylics... 

Emulsion—formation of small particles via micellar or homogenous nucleation Low dispersion viscosity compared to bulk high molecular weight good heat transfer Emulsifier impurity reactor wall fouling emulsifier impurity SBR, polyvinyl acetate, vinyl acrylics, etc. 

Figure 10. General pattern of viscosity change during bonding with cold-press glues such as the polyvinyl acetate-based, emulsion-type white and yellow glues and the animal glues. (Reproduced with permission from ref. 3. Copyright 1983 Pennsylvania State University.)...

Other attempts have been made to utilize dry powder polyvinyl alcohol and polyvinyl acetate as admixtures for the same purpose. The polyvinyl alcohol is readily soluble in water, and it requires significant amounts in addition to achieve any distinct advantages. Significant amounts of any viscosity range of polyvinyl alcohol contribute to an undesirable increase in viscosity in the cement mortar. Polyvinyl acetate in powder form has been used for this purpose with consequent improvements in working characteristics and physical properties. However, dry powder polyvinyl acetate does not form a true polymer emulsion when dissolved in water. It, therefore, may also be dissolved out of a cement mortar. 

Figure 10.2 Continuous process for production of low viscosity polyvinyl acetate in solution. (From Badr, A.L., Chem. Eng., p. 65, August 1, 1966. With permission.)...

Figure 8.23. SQELS-determined values of the transverse shear viscosity, dilational modulus and dilational viscosity for polyvinyl acetate spread at the air/water interface. After Kawaguchi et al. (1986).

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