Emulsion polymerization radiation-induced

The goal of our work was to study the gamma-radiation-induced emulsion polymerization of some less common vinyl monomers, and to obtain more reliable data by refining the experimental technique. 

Seguchi T, Suwa T, Tamura N, Takehisa M (1974) Morphology of polytetrafluoroethylene prepared by radiation-induced emulsion polymerization. J Polym Sci Polym Phys Ed 12 2567... 

Radiation Induced Emulsion Polymerization of Vinyl Chloride... 

Molecular Weight of Polyvinyl Chloride Produced by Radiation Induced Emulsion Polymerization at 25°C... 

Experiments using no emulsifier were conducted in tbe same stainless steel autoclave equipment described above (Machi et nf.. 1975). Stable latices were obtained, believed to be achieved by hydroxyl end groups and adsorbed hydroxyl ions. As with a number of the experiments with emulsifiers the polyethylene had a considerable cross-linked gel content. Finally, the same group of workers studied tbe radiation-induced emulsion polymerization of ethylene in a flow system (Kodama et al, 1974). Both potassium inyristate and ammonium perfluorooctanoate were used as emulsifiers. At longer residence times (above 0.2 hr) the rate of polymerization was essentially constant. As with the batch system it was assumed that the number of particles remained constant. In this region the rate was found to be proportional to tbe 0.3 power of the potassium myristate concentration and the 0.5 power of the dose rate, not too different from the batch systems. The kinetics was developed and estimates of tbe propagation rate constants obtained. Despite other similarities between the two systems, these were quite different, however, from those extracted from the batch experiment. 

Machi et at. (1974) first reported an investigation of the radiation-induced emulsion polymerization of tetrafluorocthylene, with ammonium perfluorooctanoate as the emulsifier. A 200-ml stainless steel autoclave, equipped with a magnetically driven propeller-type stirrer, was used. The standard recipe used was 28gm of monomer in 150 ml of water with 1% emulsifier (based on tbe water). n-Hexadecane (2.0 ml) was added to inhibit any gas-phase polymerization. The polymerizations were conducted at... 

Radiation-Induced Emulsion Polymerization Vivian T. Stannett... 

There are numerous publications about radiation-induced polymerization in homogeneous phases 2, 12,14, 29, 36) but rather little is known about radiation-induced emulsion polymerization (EP). 

Main features of radiation-induced emulsion polymerization... 

Under correctly chosen conditions (mainly an appropriate emulsifier), the radiation-chemical yield of emulsion polymerization attains very high values. For instance, if sodium lauryl sulphate is used for the radiation-induced emulsion polymerization of methyl methacrylate, we have Gp = 105, and for that of butyl acrylate, Gp = 106 molecules/100 eV. 

Ballantine (4) observed that the y-induced emulsion polymerization of styrene is about 100 times faster and yields higher molecular weights (up to 2 X 10 ) than the y-induced bulk polymerization. He explains the large difference in reaction rates by the high radical yield (G/ value) of water, as compared with the G/j value of styrene. An over-all activation energy of 3.7 kcal. per mole was calculated from the temperature dependence of the reaction. Allen et al. (1) prepared and grafted polystyrene and poly (vinyl acetate) dispersions under the influence of y-radiation. Mezhirova et al. (28) found a temperature-independent reaction rate of the y-induced emulsion polymerization of styrene. 

Other polymerization methods such as coordination polymerization," " surface electro-initiated emulsion polymerization," radiation-induced graft polymerization (RIGP)," surface thiol-lactam-initiated radical polymerization (TLIRP)" and LbL click grafting" have been employed to graft polymers from CNT surfaces. 

Gamma radiation-induced mass and emulsion polymerization of vinyl monomers has been studied by the American, Metz, and the German, Hummel. 

Gamma-Radiation-Induced Polymerization of Some Vinyl Monomers in Emulsion Systems... 

Usually, free-radical initiators such as azo compounds or peroxides are used to initiate the polymerization of acrylic monomers. Photochemical and radiation-initiated polymerizations are also well known. Methods of radical polymerization include bulk, solution, emulsion, suspension, graft copolymerization, radiation-induced, and ionic with emulsion being the most important. 

Recently, Garreau et al. (1979) reported a careful and rather detailed study of the kinetics of the radiation-induced polymerization of styrene in emulsion with sodium lauryl sulfate under conditions found earlier to lend to close agreement with simple Case 2 Smilh-Ewart kinetics (Smith, 1948). Most of the normal reaction variables were studied, and the rates of polymerization were found to be independent of the luonomer-to-water... 

Ishigure e al. (1964) reported that the radiation-induced polymerization of tetrafluoroethylene and propylene in the liquid phase produced an essentially alternating rubbery copolymer. Ito et al. (1974a) and Matsuda et al. (1974a) studied the same system in emulsion using a variety of mixed and pure emulsifiers. The experiments were conducted in a stirred 200-ml... 

Wang X., Zhang Z., Preparation of polystyrene latex particles by gamma-rays-induced emulsifier-free emulsion polymerization, Radiat. Phys. Chem., 2006,75,1001-1005. 

Radiation-induced polymerization can be carried out in bulk, in solution, in emulsion (suspension), in the gas and solid states, and in the glassy state in other words, just as in other methods of initiation (conventional, thermal, photochemical initiation, etc.). 

Hence, in order to ensure a relatively high rate of radiation-induced polymerization in the emulsion, low dose rates (0.1-1 Gy/s) and low absorbed doses are required. For all these reasons, radiation emulsion polymerization is particularly advantageous from an economical standpoint. Its activation energy, just as for other processes of radical radiation-induced polymerization, is 15-35 kJ/mol. The molecular weight of polymers increases with temperature, as in the case of typical free-radical processes (to a certain extent). This increase is due to an increase in kp with temperature, whereas k, does not depend on the temperature. 

Apart from the advantages of radiation emulsion polymerization indicated above and those characteristic of radiation-induced polymerization in general, the following advantages should also be mentioned. 

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