Polyvinyl acetate, effects

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. 

Lucie, S., Kovacevic, V., Packham, D.E., Bogner, A., Gerzina, A., Stearate-modified calcium carbonate fillers and their effect on the properties of polyvinyl acetate, composites. Proc. 2nd Int. Symp. Polymer Surface Modification Relevance to Adhesion, Newark, NJ, 24-26 May, 1999. 

The combined results of kinetic studies on condensation polymerization reactions and on the degradation of various polymers by reactions which bring about chain scission demonstrate quite clearly that the chemical reactivity of a functional group does not ordinarily depend on the size of the molecule to which it is attached. Exceptions occur only when the chain is so short as to allow the specific effect of one end group on the reactivity of the other to be appreciable. Evidence from a third type of polymer reaction, namely, that in which the lateral substituents of the polymer chain undergo reaction without alteration in the degree of polymerization, also support this conclusion. The velocity of saponification of polyvinyl acetate, for example, is very nearly the same as that for ethyl acetate under the same conditions. ... 

At a concentration of 5 to 25 wt %, increased the effective kill-life of the lindane spray up to 10 times. May have been used in chlordane and BHC insecticide formulations. In polyvinyl acetate emsulsions to impart strong bonding power in adhesives (Monsanto, 1960). 

Branching effects of polyvinyl acetate (PVAc) were... 

The effect of structural regularity on properties of polymers may be illustrated by the hydrolytic products of polyvinyl acetate (PVAc). PVAc is insoluble in water, but because of the presence of polar hydroxyl groups, partially hydrolyzed PVAc is soluble in water. 

When tested in other polymers, maleimides did not affect the rate of cross-linking in polydimethylsiloxane, polyisobutylene, and polyvinylchloride. In polyethylene, the addition of 5 wt.% of m-phenylene dimaleimide increased the G(X) from 1.8 to 7.2. In the polyvinylacetate the effect was even more pronounced the dose for gelation was reduced by about a factor of 50. Contrary to the cross-link enhancing effect found for m-phenylene dimaleimide, cross-linking was retarded in polyvinyl acetate by the addition of monomaleimides. When analyzing the mechanism of the reaction it was concluded that monomaleimides are not expected to affect cross-linking in saturated polymers. ... 

Long,V.C. Thesis The effect of branching on the dilute solution and bulk properties of polyvinyl acetate. University of Michigan 1958. 

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... 

The observations in Sect. 2.6.1 clearly apply to the barrier effects in Fig. 2.62 especially with regard to the moisture or water vapor permeability. The permeability of water vapor for polyvinyl alcohol is unacceptable compared to acceptable levels in polyvinyl acetate, polybutyral and cyanoacrylate. A high level of moisture... 

Fig. 2.60 Topological views of formulated polyvinyl acetate over agar (a) and plain agar (b) in Petri dishes after having been inoculated with Staphylococcus aureus and incubated for 7 days at 37°C note the original yellow drop of bacteria suspension in (a) and the prolific growth in (b) which demonstrates the barrier effect...

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. 

EFFECT OF NON-IONIC SURFACTANT ON THICKENING OF POLYVINYL ACETATE-SODIUM LAURYL SULFATE (NaLS) ( 1)... 

O Reilly, J. M. The effect of pressure on glass temperature and dielectric relaxation time of polyvinyl acetate. J. Polymer Sci. 57, 429—444 (1962). 

Sharonov, Yu. A., andM. V. Volkenstein Co-operative effects in the annealing and softening range of polyvinyl acetate. Vysokomol. Soed. 4, 917—921... 

For the reaction of polyvinyl acetate radicals and substituted phenols (Fig. 1), Simonyi et al. (1967c) suggested a Hammett-type correlation for the isotope effect dependence ... 

The latter compound and its substituted derivatives readily react with polyvinyl acetate radicals. Substituents in the aromatic ring were found to influence the reactivity of the hydroxylamine slightly p = — 0-16 0-04 (Simonyi et al., 1967a). In comparing this value with those of phenols, the decreased substituent effect can be rationalized by considering two factors. First, the 0—H bond is more remote from the aromatic ring in hydroxylamine than in phenol. Second, the stability of phenyl nitroxide radicals is higher than that of phenoxy radicals. It is... 

To improve the properties of PLA, plasticizers, special additives such as chain-extenders, polymer blends, and composites are commonly investigated. Martin and Averous (10) have studied the effects of various plasticizers on the properties of PLA. Pilla et al. (11-12) have investigated the effects of chain-extenders on the foaming properties of PLA. In addition, a vast number of studies have been conducted to enhance the properties of PLA by blending it with various polymers such as polyethylene oxide (PEO), polypropylene oxide (PPO), polyvinyl acetate, polyolefins, polystyrene, HIPS (high impact polystyrene), polyacetals, polycarbonate, and acrylonitrile butadiene styrene (ABS) (13-26). 

Polyvinyl acetate emulsions for manual application in the production of adhesive bound books were examined for stability. It was found, among other things, that plasticized homopolymers had poor or moderate stability, while copolymer types showed very high stability. The addition of calcium carbonate and calcium acetate could improve the lasting qualities of unstable materials but had little effect on the very stable ones. The addition of these buffering agents made the adhesive less acid and less damaging to papers (6). 

Possible Effect of Charged End-groups. A possible reason for differences between samples might be the process used for polymerising the original polyvinyl acetate. Emulsion polymerisation is likely to introduce a proportion of ionic (sulphate or carboxyl) end-groups which would not be expected if bulk polymerisation with benzoyl peroxide had been used. An Antweller Microelectrophoresis apparatus was used to measure rates of electrophoresis of polyvinyl alcohols in solution in a pH 7.8 phosphate buffer. No significant difference was observed between... 

We originally suggested - that trauisfer to the polyvinyl alcohol could explain the effect of Elvanol 32-22 in reducing the rate of polymerisation of vinyl acetate solutions. The importance of this transfer reaction has recently been confirmed by Dimonie et al.(6) who use ferrous ion/hydrogen peroxide redox Initiation. However Okamura, Yamashlta, and Motoyama determined the transfer rate constant of vinyl acetate to polyvinyl acetate and polyvinyl alcohol in homogeneous solution they found for... 

The effects of commercial grades of polyvinyl alcohol obtained from several manufacturers on the rate of polymerisation of vinyl acetate aqueous solutions and emulsions initiated by potassium persulphate at 60°C have been investigated. Increasing concentrations of polyvinyl alcohol in the same range tend to reduce the rate of polymerisation of the solutions but Increase the rate of polymerisation of emulsions. Considerable differences were noted between the effects of nominally simileir grades from different sources. Attempts to correlate the effect on the rate of polymerisation of vinyl acetate solutions with the acetyl content and molecular weight of the polyvinyl alcohol appear to have been confounded by an uncontrolled variable. A subsequent publication from the U.S.S.R. indicates that this may be the concentration of a by-product formed during the hydrolysis of the polyvinyl acetate. Other factors which may account for the effects are also discussed. 

Povidone can also be used as a hydrophilic component or pore former in preparations that contain sustained-release auxiliaries like polyvinyl acetate, cellulose derivatives like HPMC [490, 509, 660], alginate [461], cetylacohol [600], polylactic acid [5o6],Gelucire [510],polyvinyl alcohol [522],ceresine wax [523], stearic acid [606] or methacrylate copolymers [491] to control or regulate the release of active substances, as binders and/or sometimes as plasticizers. They can also be extruded together with the active substance in melted stearyl alcohol and filled into hard gelatin capsules to achieve the same effect [471]. Ocular delivery systems are also described [598]. 

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