Semicontinuous emulsion polymerization of vinyl acetate IX. Decomposition of the initiator

Abstract

The way in which the decomposition reaction of a persulfate initiator is influenced by the nature of reactants of the polymerization medium and by the working conditions during the semicontinuous polymerization and copolymerization of vinyl acetate is studied. The rate of the splitting reaction of potassium persulfate is higher in the aqueous phase containing a protective colloid and surfactant. The splitting rate is smaller in the presence of vinyl acetate. The presence of hydrophobic comonomers decreases the rate ofinitiator decomposition. An increase of the addition rate of monomers leads to an increase of the obtained polymer and of the splitting rate of the initiator. Semikontinuierliche Emulsionspolymerisation von Vin.dacetat. IX. Zer.~etziingsreuktion rles InitiatorsDer EinfluD der Reaktanten im Polymerisationsmedium und der Reaktionsbedingungen auf die Zersetzungsreaktion eines Persulfatinitiators wird untersucht. Die Geschwindigkeit der Spaltungsreaktion von Kaliumpersulfat steigt bei Anwesenheit eines Schutzkolloids und einer oberflkhenaktiven Substanz in der wPDrigen Phase. in Gegenwart von Vinylacetnt ist die Spaltungsgeschwindigkeit niedriger. Bei Anwesenheit hydrophober Comonomere nimmt die Zersetzungsgeschwindigkeit dcs Initiators ab. Ein Anstieg der Zufiihrungsgeschwindigkeit der Monomere erhoht die Menge an erhaltenem Polymer und die Spaltungsgeschwindigkeit des Initiators. DONESCU and FUSULAS: Scmicontinuous emulsion polymerizntion of vinyl acetate. 1X Systcm')Acta Polymcriu 42 (1Wl) Nr. 10

Microemulsions of a Vinyl Acetate/2-Ethylhexyl Acrylate Monomer Mixture

“…These results, supplemented with the data published so far, [3][4][5][6][7][8]12,15,17 evidence the usefulness of the conductometric method in uncovering structural changes of microemulsions that contain monomers. The concentration domain A corresponds to the o/w type microemulsions, B to bicontinuous ones, and C to w/o ones.…”

“…In surfactant/SCC/water systems the existence of hydrocarbonated zones does not represent an argument in favor of micellization. RES 16 and surface tension measurements 11 could not evidence the micellization of NPEO 25 in alcohol/water mixtures. To characterize the structure of alcohol type cosurfactants in solutions, critical microstructuring concentrations were established which depend on the chemical nature of the partners.…”

“…The formation of microemulsions is based on the very pronounced decrease of the interfacial tensions between organic and aqueous phases . In the case of a PrOH/H 2 O mixture the air/liquid interfacial tension decreases with increasing alcohol concentration and, above a certain concentration, it is no longer modified by the presence or nature of the surfactant . Therefore in “surfactant-free” systems one can obtain microemulsions only above the high PrOH concentration range (Figures a and a) while in the presence of the surfactant they may be formed over concentration ranges rich in aqueous phase (Figures b and b).…”

“…26 In the case of a PrOH/H 2 O mixture the air/liquid interfacial tension decreases with increasing alcohol concentration and, above a certain concentration, it is no longer modified by the presence or nature of the surfactant. 11 Therefore in "surfactant-free" systems one can obtain microemulsions only above the high PrOH concentration range (Figures 1a and 2a) while in the presence of the surfactant they may be formed over concentration ranges rich in aqueous phase (Figures 1b and 2b). The increase of the more hydrophobic EHA comonomer concentration reduces the number of microemulsions in the presence of NPEO 25 from 29 (VAc/EHA ) 80/20) to 26 (VAc/EHA ) 50/50).…”

“…Nonylphenol ethoxylate monomaleate resulted from the reaction between NPEO25 and maleic anhydride 1 mol/1 mol, at 65 °C for 3 h. 22 The homogeneous systems, microemulsions, were obtained as in previous contributions. [15][16][17]23 PrOH mixtures: 10/90, 30/70, 50/50, 70/30, and 90/10 (w/w). Each mixture was added to nine ratios (1/9 to 9/1) of organic phase with aqueous phase (w) which contained 33% surfactant or plain water.…”