Emulsion polymerization of chloroprene. II. Molecular weights

Morton, Maurice; Piirma, Irja

doi:10.1002/pol.1956.120199316

Cited by 13 publications

(2 citation statements)

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“…1,2 For both technological and fundamental interest, the emulsion polymerization of CP has been intensively investigated. Industrially, poly(CP) is produced by the free radical emulsion polymerization of CP, in which xanthogen disulfide or mercaptan is employed as a conventional mediating chain transfer agent to regulate the molecular weight of the product.…”

Section: Introductionmentioning

confidence: 99%

“…Industrially, poly(CP) is produced by the free radical emulsion polymerization of CP, in which xanthogen disulfide or mercaptan is employed as a conventional mediating chain transfer agent to regulate the molecular weight of the product. 1,2 For both technological and fundamental interest, the emulsion polymerization of CP has been intensively investigated. 3,4 Anionic surfactants such as rosin or sulfonic acid species or nonionic surfactants such as poly(vinyl alcohol) or poly(oxyethylene) species are frequently employed to achieve a stable emulsion.…”

Section: Introductionmentioning

confidence: 99%

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RAFT‐mediated emulsion polymerization of chloroprene and impact of chain‐end structure on chloroprene rubbers

Ishigaki

Mori

2017

J of Applied Polymer Sci

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The reversible addition-fragmentation chain transfer (RAFT) polymerization of chloroprene (CP) in an emulsion system using a dithiocarbamate-type RAFT agent was studied. The controlled RAFT-mediated emulsion polymerization was achieved by the appropriate combination of a RAFT agent and nonionic surfactant (polyoxyethylene phenyl ether) using a water-soluble initiator (VA-044) at 35 8C. An almost linear first-order kinetic plot was observed until relatively high conversion (>80%) with molecular weights between 22,300 and 33,100 and relatively narrow molecular weight distributions (M w /M n Ϲ 1.5) were achieved. The amount of the emulsifier used and the pH of the system were found to affect the controlled character, polymerization rate, and induction period, which are related to the size of the emulsion particles. Large-scale RAFT-mediated emulsion polymerization was also employed to afford industrially applicable poly(CP) (M w > 25 3 10 4 , resulting product > 2300 g). The vulcanized CP rubber obtained from the RAFT-synthesized poly(CP) exhibited better physical properties, particularly tensile modulus and compression set, which may be due to the presence of the reactive end groups and the absence of low-molecular-weight products. We also evaluated the impact of the chain-end structure on the mechanical and physical properties of these industrially important CP rubbers with carbon black.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

RAFT‐mediated emulsion polymerization of chloroprene and impact of chain‐end structure on chloroprene rubbers

Ishigaki

Mori

2017

J of Applied Polymer Sci

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Emulsion polymerization. IV. Experimental verification of the theory based on slow termination rate within latex particles

Gardon

1968

J. Polym. Sci. A‐1 Polym. Chem.

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SynopsisA large body of data shows that the time dependence of conversion fits the equation P = At2 + Bt in the interval where, according to the Smith-Ewart model, the relationship should be linear. For latexes of very small particle size the Smith-Ewart linear relationship (P = Bt) is often observed, and for latexes of very large particle size the conversion was found to be proportional to te. The experimental value of parameter B was in good agreement with independent theoretical predictions. From A and B the ratio between termination and propagation constants was calculated and was in the 5-200 range. Independent estimates of this ratio give the same order of magnitude. These independent estimates are from the literature and are obtained from the increase in conversion rate at catalyst post-addition during emulsion polymerization or from emulsion polymerization initiated by intermittent irradiation or from homogeneous polymerization in the presence of inert polymers of high viscosity. The conversiontime curves describing the whole conversion process generally have sigmoid shape. The molecular weight is often found to pass through a maximum as the conversion increases. In one experiment this maximum coincided with the calculated maximum in the average number of radicals per particle &. The variation of experimental molecular weights with conversion accurately followed the theoretical predictions. The deviation from the Smith-Ewart model was often significant. The value of & was not 0.5, as the Smith-Ewart model requires it to be, but often reached values much larger, as large as 10.The particle size distribution broadened with increasing conversion and became increasingly skew. Numerous data taken from the literature are in good quantitative or qualitative agreement with the theory proposed in Part I11 and for these data the observed deviations from the Smith-Ewart theory are readily explainable. The new data obtained with styrene, n-butyl methacrylate, and methyl methacrylate are also in quantitative agreement with the new theory. One experiment involving methyl methacrylate is analyzed in great detail. The variation of time, of &, of molecular weight, of average particle size, and of particle size distribution with conversion are reported. The molecular weight distribution is also calculated from the conversion dependence of molecular weight.

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