摘要:

AbstractThe following mechanism is proposed for latex film formation. Initially, the latex particles move about freely, with characteristic Brownian motion. As the water evaporates, their motion becomes more restricted, and eventually the water‐air interfacial tension forces them together in a packed array, with their double layers hindering their further mutual approach. The continued evaporation of the water exerts a force to overcome this repulsion, so that the double layers are ‘ruptured’ and a polymer‐polymer contact is formed. This brings the polymer‐water interfacial tension into play, to reinforce and complement the water‐air interfacial tension. If the combined forces are sufficient to deform the polymer spheres, they form a continuous film. This film becomes more homogeneous upon ageing; there occurs a further gradual coalescence, the rate of which depends upon the polymer structure and during which any incompatible substance is exuded to

ISSN:0007-1641    

DOI:10.1002/pi.4980020301

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe preparation of positively charged polyvinyl acetate emulsions and measurement of their adsorption characteristics are described. The properties of two representative preparations, a homopolymer and a vinyl acetate‐alkyl acrylate copolymer, are given. The high adsorption of cationic emulsions makes them suitable for papers or boards which require a high polymer content to modify the properties of the sheet. Their use in the preparation of thermoplastic board is discusse

ISSN:0007-1641    

DOI:10.1002/pi.4980020302

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe connexion between heat‐seal and pressure‐sensitive adhesives, including delayed‐tack heat‐seal adhesives, is illustrated in chemica

ISSN:0007-1641    

DOI:10.1002/pi.4980020303

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe application of new methods for diffusion measurements by micro‐floats has been studied. A modified Gerlach method, the method of a float moving through the concentration gradient, and an electromagnetic balancing method were tried. It was found that by the last method coefficients of diffusion of macromolecules in solution can be measured. Experiments have been carried out using trimethyl trimesate in methanol and two sharp fractions of polystyrene in cyclohexane at the theta temperature. The results are compared with literature dat

ISSN:0007-1641    

DOI:10.1002/pi.4980020304

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractEthylene‐vinyl acetate (E‐VA) copolymers consist of a range of materials beginning with polyethylene and possessing a gradation of properties with increasingly higher concentrations of vinyl acetate (V‐OAc). The major property differences between E‐VA copolymers and polyethylenes which incorporation of V‐OAc confers are discussed with reference to processing and packaging app

ISSN:0007-1641    

DOI:10.1002/pi.4980020305

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractIn the oxidative condensation of 2,6‐dimethylphenol catalysed by copper compounds, poly(2,6‐dimethylphenylene oxide) was formed as a particulate solid in both pyridine and pyridine‐methanol mixtures. No quinone was produced when the volume fraction of pyridine exceeded 15%. The rate of polymerisation was independent of monomer concentration and first order with respect to catalyst concentration. This first‐order dependence ceased when catalyst concentrations exceeded 4 × 10−2molar. Above this concentration the polymerisation rate is probably controlled by mass transfer of oxygen from the gas to the liquid phase. The rate of polymerisation increased as the volume fraction of methanol increased. A reaction mechanism is proposed to account for the kinetics; this involves a reversible step.Particle sizes of the dispersed polymers have been measured.Heterogeneous systems can be used to produce polymers of higher molecular weights than those obtained in soluti

ISSN:0007-1641    

DOI:10.1002/pi.4980020306

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe course of emulsion polymerisation is shown to depend on the water‐solubility of the monomers concerned. With insoluble monomers, the mass transfer rate of monomer to polymer particles can sometimes be exceeded by the polymerisation rate, and viscosity within the particles is appreciable throughout the course of the reaction. Thus, surfactant is adsorbed before monomer droplets disappear. With more soluble monomers, mass transfer rates of monomer are high and since the equilibrium concentration of polymer in particles is low the monomer droplets disappear early in the reaction. Consequently, water‐insoluble monomers often conform to Smith‐Ewart behaviour, whereas water‐soluble monomers do not. With water‐soluble monomers the final particle number is proportional to the cube of the initial surfactant conc

ISSN:0007-1641    

DOI:10.1002/pi.4980020307

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe suspension polycondensation of phenol sulphonic acid and its homologues with formaldehyde, to produce a satisfactory cation exchanger in the bead form in the presence of sulphuric acid catalyst, was investigated. The various reaction conditions for bead formation, using an organic liquid suspending medium in the presence of a suspension stabiliser, such as the nature and quantity of the suspension stabilisers, the quantity of water added, the nature and quantity of the organic suspending medium and the rate of mixing, were studied.o‐Dichlorobenzene was the best organic suspending liquid and a chemically peptised colloidal kaolin suspension was a good suspension stabiliser in the presence of a wetting agent. The optimum reaction conditions were given.The best exchangers were obtained in good yields using a molar ratio of phenol: HCHO:H2SO4of 1·0:2·5:1·5 or a mixture of equimolecular amounts of phenol and resorcinol in a molar ratio of mixed phenols: HCHO: H2SO4of 1·0:1·0:1·5.The efficiency of all the products obtained was measured by determination of their total exchange c

ISSN:0007-1641    

DOI:10.1002/pi.4980020308

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980020310

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

ISSN:0007-1641    

DOI:10.1002/pi.4980020312

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY