ISSN:0007-1641    

DOI:10.1002/pi.4980020101

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractKinetic data on the emulsion polymerisation of styrene are discussed in the light of the Smith‐Ewart theory as modified by Gardon. It is shown that at least in the beginning of the reaction serious discrepances exist between experimental results and the theoretical concept. An electrolytic effect in cationic emulsifier systems was found. Emulsion polymerisation of vinyl acetate was investigated and the mechanism is discussed. The polymerisation of vinyl acetate in aqueous solution without added emulsifier begins as a true solution polymerisation but very soon changes to a suspension polymerisation. The latex particles formed are an order of magnitude larger than those obtained in the emulsion polymerisation and have a very narrow size distribution. There seems to be a very short period of particle formation in this syste

ISSN:0007-1641    

DOI:10.1002/pi.4980020102

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractAn investigation of continuous emulsion polymerisation kinetics was carried out using a series of three continuous stirred tank reactors (CSTR), and styrene and methyl acrylate as types of monomer with different solubilities in water.Steady‐state conversion fluctuations reported in the literature could be suppressed by holding the feed rates constant.The results obtained are only partly in agreement with the theory proposed by Gershberg&Longfield, who combined the basic assumptions of the Smith‐Ewart theory with steady‐state CSTR kinetics.An explanation for the deviations from this theory is therefore suggested which takes into account the tendency of relatively water‐soluble monomers to form particles from the homogeneous solution and to undergo so‐called interparticle termination as a result of migration of radicals between the latex

ISSN:0007-1641    

DOI:10.1002/pi.4980020103

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractA wide range of compounds of the Group VIII metals has been investigated as possible catalysts for the polymerisation of butadiene and isoprene in the aqueous phase. The compounds studied included the fluorides, chlorides, bromides, iodides, nitrates and sulphates, and also certain chelate complexes of the Group VIII metals. Substantial amounts of polybutadiene were obtained using rhodium chloride, rhodium bromide, iridium chloride, platinous iodide, and iron (III) acetylacetonate. The first three gave stereoregular (hightrans‐1,4‐) polybutadiene; the last two gave mixed microstructures. With isoprene, significant polymerisation was observed with iridium chloride, platinous iodide, and iron (III) acetylacetonate. In each case, the product was non‐stereoregular.A more detailed study of the rhodium chloride‐butadiene system has indicated that the locus of the polymerisation is the aqueous phase, probably the surfactant micelles. A mechanism for the polymerisation has been proposed in the light of these results. This mechanism suggests certain predictions regarding the effects of chloride ions and of isoprene upon the polymerisation rate. These predictions have been tested experimentally, as also has the prediction that the polymer should contain chemically combined sur

ISSN:0007-1641    

DOI:10.1002/pi.4980020104

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractExperiments are described in which the rate of radical production, in the emulsion polymerisation of vinyl chloride, has been increased or decreased in the course of the reaction. The results strongly support previous conclusions. The mechanism of desorption and re‐absorption of radicals and the kinetic consequences of the interparticle termination are discusse

ISSN:0007-1641    

DOI:10.1002/pi.4980020105

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe influence of the chemical structure of the emulsifier on the rate of polymerisation, the yield and the properties of the polymer in the emulsion polymerisation of vinyl chloride was studied. The highest molecular weights were obtained with the sodium salts of the sulphuric acid esters of fatty alcohols with a chain length of 10 and 18 C atoms. In the group of aliphatic sulphonates, sulphates and salts of fatty acids there was no great difference. In general the effect of emulsifiers increases with the chain length. Unsaturated emulsifiers decrease the rate of polymerisation. Non‐ionic emulsifiers are less active than ionic one

ISSN:0007-1641    

DOI:10.1002/pi.4980020106

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractA small‐scale calorimetric method developed for following the rate of polymerisation of monomers in solution and in bulk has now been adapted by construction of a stirred reaction vessel for the study of rates of emulsion polymerisation recipes. Results obtained for the emulsion polymerisation of methyl methacrylate are compared with those for polymerisation under bulk condition

ISSN:0007-1641    

DOI:10.1002/pi.4980020107

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe problem of particle formation in aqueous solutions of vinyl acetate is treated according to the Deryaguin‐Landau‐Verwey‐Overbeek (D.L.V.O.) theory of the stability of lyophobic colloids.In the absence of surfactants, polymer particles are stabilised by ionic end‐groups derived from persulphate initiator. Palit's dye partition method is used to determine the number of these end‐groups and the amount of adsorbed sodium dodecyl sulphate which was used as emulsifying agent in some experiments; this enables the electrical forces of repulsion between particles to be calculated. The Hamaker constant which defines the magnitude of the van der Waals' forces of attraction between particles has been estimated for polyvinyl acetate. The dependence of the stability of the polymer dispersion formed on the concentrations of initiator, emulsifier, etc. is investigated; the observations accord with expectations on the basis of D.L.V.O. theory. It is shown that small particles are unstable with respect to coalescence with larger particles. The processes of polymerisation and particle growth are essentially independent in th

ISSN:0007-1641    

DOI:10.1002/pi.4980020108

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe incentives and problems associated with 100W conversions of polymerisation are discussed with reference to the heterogeneity produced by emulsion polymerisation of styrene‐butadiene rubbery copolymers. Stereospecific problems are also considered together with the influence of latex particle size and particle size distribution on viscosity and solids content and film‐forming propert

ISSN:0007-1641    

DOI:10.1002/pi.4980020109

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe adverse effect of water on aluminium‐epoxide bonds has been studied with respect to: the temperature and water vapour pressure of the exposure environment; the degree of cure of the adhesive; and the recover‐ability of the bond strength. The results confirm that water accumulation within the system is the disrupting entity. However, the current data indicate that hydrolysis of covalent bonds, rather than interference with hydrogen bonding, is the operative mechan

ISSN:0007-1641    

DOI:10.1002/pi.4980020110

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY