PVAc latexes

We have found that in the system of presulfate initiator, the PVAc latexes are not dissolved transparently in the methanol-water mixture [8], and in the system of HPO initiator, the extraction of the polymer from the PVAc latex films with acetone greatly depends on the polymerization condition [9]. These results suggest that if a polymerization method can be found in which the grafting polymerization of VAc onto PVA is controlled to the minimum, a large portion of PVAc in the latex film will have a chance of extraction with solvents. In this Chapter, the preparations of the unique porous films from the PVAc latexes containing PVA as a protective colloid by an extraction of the PVAc particles with acetone and the characteristic properties of the porous films are summarized. 

There are three important processes for preparing PVAc latexes in the presence of PVA as a protective colloid batch, semi-continuous, and delayed addition of monomer [10]. In this Chapter, the effects of the addition of VAc and initiators on the properties of PVAc latexes are discussed using the three methods under the same charge of ingredients for polymerization as shown in Fig. 1 [1,11]. 

In methods [1] and [III] using APS, the PVAc iatexes coagulated during polymerization or cooling. In the HPO-TA system, stable PVAc latexes were formed using high conversion in every polymerization method. The results of the polymerization and properties of the PVAc latexes obtained are summarized in Table 1 [11]. 

In order to prepare the PVAc latexes with Newtonian character or dilatancy behavior, the polymerization... 

As mentioned previously, the properties of the PVAc latexes prepared in the presence of PVA have something to do with the reaction between PVA and initiators during the polymerization. 

The PVAc latex was cast 1.8 mm in thickness on a poly(-ethylene) plate and dried at room temperature. The latex film was dried further in a vacuum desiccator for 24 h, and extracted in Soxhlet extractor with acetone for 20... 

Figure 2 Electron microphotographs of crack surface (a) and (b) and upper surface (c) and (d) of PVAc latex film. Acetone extraction (a) and (c) before, (b) and (d) after.

Figure 3 Formation model of porous PVA film from PVAc latex.

There has been a conventional sense that the PVAc latexes prepared in the presence of PVA as a protective colloid contain the graft copolymer of PVA and PVAc, so that PVAc particles in the dried latex film are not extracted at a high ratio with solvents. In this Chapter, it has been defined without an influence by the usual sense that the porous PVA-PVAc composite can be prepared from the PVAc latex film with acetone extraction. The porous film consists of the spherical cells of PVA... 

The determination of adsorption isotherms at liquid-solid interfaces involves a mass balance on the amount of polymer added to the dispersion, which requires the separation of the liquid phase from the particle phase. Centrifugation is often used for this separation, under the assumption that the adsorption-desorption equilibrium does not change during this process. Serum replacement (6) allows the separation of the liquid phase without assumptions as to the configuration of the adsorbed polymer molecules. This method has been used to determine the adsorption isotherms of anionic and nonionic emulsifiers on various types of latex particles (7,8). This paper describes the adsorption of fully and partially hydrolyzed PVA on different-size PS latex particles. PS latex was chosen over polyvinyl acetate (PVAc) latex because of its well-characterized surface PVAc latexes will be studied later. 

Figure 2 The upper critical flocculation temperature is shown plotted against the applied pressure. refers to the PMMA latex while, o refers to the PVAc latex. The solid line represents 9 conditions for a solution of PIB + 2-methylbutane while the dashed line represents the theoretically calculated UCFT as a function of pressure.

When pressure is applied to the latex, the UCFT is seen to move to higher temperatures as indicated in Figure 2. It was found that the PMMA latex stabilized by PIB of Mn - 2 x lCrcould be fitted to the same curve as the PVAc latex stabilized by PIB of Mjj 4 x 10. A linear regression analysis of the UCFT as a function of applied pressure gave ... 

Edelhauser (3) has explained his results on the interaction of anionic surfactants (sodium lauryl sulfate and sodium dodecyl-benzene sulfonate) with a PVAC latex as a two-step mechanism involving surface adsorption followed by surfactant penetration into... 

Presence of non-ionic surfactants such as Igepal CO-630 seems to prevent the thickening of PVAC latex by NaLS, as shown in Table IV. This can be interpreted as to show that the presence of non-ionic surfactant at the PVAC latex surface prevents the penetration of NaLS into the particle. 

Polyfvinyl acetate) (PVAc) latexes produced by batch and continuous emulsion polymerization were used in this study. Details for the apparatus and the polymerization procedure can be found in Penlidis et al. (6,12,K3). Samples taken during the reaction were subsequently analyzed to follow conversion- and particle growth-time histories. The batch experimental runs were designed to yield similar conversion-time histories but different particle sizes. Conversion was measured both off-line, by gravimetric analysis, and on-line using an on-line densitometer (a U-tube DPR-YWE model with a Y-mode oscillator with a PTE-98 excitation cell and a DPR-2000 electronic board by Anton Paar, Austria). A number of runs were repeated to check for reproducibility of the results. Four batch runs are described in Table I below and their conversion histories are plotted in Figure 1. 

A dry packed column with porous material was used for the characterization according to size of the PVAc latex samples. The packing employed was CPG (Controlled Pore Glass), 2000 A, 200-400 mesh size. Deionized water with 0.8 gr/lit Aerosol O.T. (dioctyl sodium sulphosuccinate), 0.8 gr/lit sodium nitrate and 0.4 gr/lit sodium azide served as the carrier fluid under a constant flowrate. The sample loop volume was 10 pC A Beckman UV detector operating at 254 nm was connected at the column outlet to monitor particle size. A particle size-mean retention volume calibration curve was constructed from commercially available polystyrene standards. For reasons of comparison, the samples previously characterized by turbidity spectra were also characterized by SEC. A number of injections were repeated to check for the reproducibility of the method. 

Polyvinylacetate (PVAc) has not been used in the pharmaceutical held until recently. During the polymerization, especially at high conversion, free radicals are transferred to dead polymers, resulting in the formation of branched polymers. These branched polymers are susceptible to deterioration. Because the PVAc latex particles are produced by an emulsion polymerization technique, this provides a good process for the water-based dispersion in him coatings. The main purpose of this polymer is the him coating of sustained release dosage forms. The polymer is used as a precursor in the production of polyvinylalcohol (PVA), which cannot be prepared directly by polymerization due to the unstable, isomeric monomer of acetaldehyde. 

Figure 4. (top) Effect on polymerization rate of solutions at 60° C. (bottom) Adsorption isotherms at 20° C on PVAc latex. 

Keyclde . [Witco] Tributyltin oxide mildewcid antimicrobial for PVAc latex paints. 

The effect of plasticizer (i.e., dibutyl phthalate) content in PVAC latexes on the strengths of PVAC-modified mortars is represented in Fig. 4.12.i i Like SBR-modified mortars, the strengths are governed by the nature of polyvinyl acetate (with variation of the plasticizer content), and is reduced with an increase in the plasticizer content. 

Figure 4,12 Effect of plasticizer content in PVAC latexes on flexural and compressive strengths of PVAC-modified mortars.

CAS 111-77-3 EINECS/ELINCS 203-906-6 Uses Solvent for coatings incl. nongrain-raising wood stains, printing inks, dye pastes for textiles coalescing aid tor PVAc latex paints solvent in stamp pad and stencil inks diluent tor hydraulic brake fluids deicer in jet fuel deactivator in pesticides coalescent for floor polishes solvent in cosmetics... 

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