Emulsion Polymerization of Vinyl Acetate

El‐Aasser, M. S.; Vanderhoff, J. W.

doi:10.1007/978-94-009-8114-0

Cited by 53 publications

(1 citation statement)

References 42 publications

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“…In general, particle stabilization is achieved by the use of various surfactants which are employed in emulsion polymerization formulations. The anionic and nonionic surfactants are the most widely utilized because of en-hanced compatibility with negatively charged latex particles (usually as a result of persulfate initiator fragments) as compared to other emulsifiers [3][4][5]. Recent years, particle stabilization can be achieved via novel surfactants such as oligomeric, polymeric, AB type, ABA type etc.…”

Section: Introductionmentioning

confidence: 99%

Emulsion Polymerization of Vinyl Acetate in the Presence of a New Cationic Surfactant

Saraç¹,

Şenkal²,

Yildirim³

2014

AJAC

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In this study, the emulsion homopolymerization system containing vinyl acetate, potassium persulfate, a new cationic polymeric surfactant and water was studied by the applying semi-continuous emulsion polymerization process. The effects of new polymeric emulsifier on the physicochemical properties of obtained vinyl acetate latexes were investigated depending on vinyl acetate percentage in the polymerization recipe, and two thermal initiators in homopolymerization.

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Section: Introductionmentioning

confidence: 99%

Emulsion Polymerization of Vinyl Acetate in the Presence of a New Cationic Surfactant

Saraç¹,

Şenkal²,

Yildirim³

2014

AJAC

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Emulsion polymerization of styrene with disproportionated rosin acid soap as emulsifier

Mayer

Meuldijk

Thoenes

1996

J of Applied Polymer Sci

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In the industrial production of rubbers and latices, disproportionated rosin acid soap (DRAS) is often applied as an emulsifier. Titov et al.' showed that phenanthrenetype cyclic compounds with aliphaticor aromatic-type double bonds, which are present in DRAS, may act as a chain-transfer agent. As a result of radical transfer to these chain transfer agents, the rate of radical desorption from the particles into the water phase is enhanced. For batch emulsion polymerizations with DRAS as an emulsifier, Mayer et al.2,3 showed that limited particle coagulation occurs in interval 2. In spite of the decrease of the particle concentration, the polymerization rate was not significantly influenced. Apparently, the effect of the decrease of the particle number is compensated by the increase of the average number of growing chains per particle. This result is typical for emulsion polymerizations where radical desorption and radical absorption are of the same order of magnitude, i.e., Smith and Ewart case 1 kinetic^.^^^ Mayer et al.'s3 also showed that the polymerization rate in a latex with DRAS as an emulsifier can be predicted over a wide range of operating conditions with the solution of the radical population balance over the particle-size distribution and a proper rate coefficient for radical desorption, kdes. The value of kdes depends on the concentration of DRAS in the recipe.However, there is possibly another mechanism by which most experimental results obtained by Mayer et al. can be explained Nonmonomeric compounds with a double bond which are present in DRAS may react with a growing chain. When the chain-end radical formed in this way propagates a t a very slow rate, the characteristic time for propagation may even be considerably longer than the characteristic time for absorption of a second radical and subsequent instantaneous bimolecular termination. This means that a significant number of growing chains are excluded from the propagation process so that the growth rate of the particles is considerably retarded. According to this mechanism, the unsaturated compounds present in DRAS are built into the polymer chains. The total effect is a decrease of the initiator efficiency. Since the rate of radical absorption increases with increasing particle diameter, inhibited radicals are terminated at a faster rate in large particles than in small particles.increase of the radical absorption rate with increasing particle diameter causes the polymerization process in large particles to be restarted a t a faster rate than in small particles. This leads to a more pronounced dependence of the growth rate on the particle diameter, making the polymerization process similar to a process where radical desorption is dominant. Note that, the "desorption mechanism" and the "inhibition mechanism" predict a similar molecular weight (distribution).Whether the "desorption mechanism" or the "inhibition mechanism" will be dominant depends on the ratio of the total rate coefficient for radical transfer k, and the rate coefficient for pr...

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Electrostatic effects on the polymerization of vinyl acetate in three-component anionic microemulsions

Sosa¹,

López²,

Peralta³

et al. 1999

Macromol. Chem. Phys.

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SUMMARY: The polymerization of vinyl acetate (VA) in three-component microemulsions stabilized with Aerosol OT is examined as a function of pH. To investigate the role of electrostatic effects on the polymerization kinetics, two initiators (potassium peroxodisulfate and V-50) that decompose into negatively-charged and positively-charged free radicals, respectively, were used. The pH of the reacting medium influences the efficiency of potassium peroxodisulfate (KPS) to initiate the reaction but it has no effect on V-50 efficiency. At neutral pH, faster reaction rates and higher conversions (after 90 min) are achieved with KPS. At equal free radical fluxes and pH's, KPS gives faster reaction rates and larger conversions than V-50 because of the different electrostatic interactions of KPS and V-50 free radicals with the negatively-charged microemulsion droplets and the reacting particles. Final latices contain nanosize polymer particles with particle size of ca. 30 nm in reactions initiated with KPS and between 26 and 40 nm in polymerizations initiated with V-50. In all cases, linear poly(vinyl acetate) is obtained because chain transfer to monomer is the controlling mechanism of chain growth, even at high conversions. This appears to be due to the small particle size that allows the fast desorption rate of the monomeric free radicals from the particles.

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Emulsion Polymerization of Vinyl Acetate

Cited by 53 publications

References 42 publications

Emulsion Polymerization of Vinyl Acetate in the Presence of a New Cationic Surfactant

Emulsion Polymerization of Vinyl Acetate in the Presence of a New Cationic Surfactant

Emulsion polymerization of styrene with disproportionated rosin acid soap as emulsifier

Electrostatic effects on the polymerization of vinyl acetate in three-component anionic microemulsions

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