摘要:

AbstractA rapid test procedure has been devised for determining the effect of environment on the mechanical properties of polymeric materials and on the strength of adhesive joints. The adverse effect of water on aluminium‐epoxide joints has been confirmed, but the effect has been shown to be due to a stress‐hydrolysis of primary chemical bonds rather than interference with hydrogen bonding. The use of scanning electron microscopy has shown that joints tested in dry conditions fail in adhesion, while those tested in aqueous environments fail within a boundary layer. The presence of high concentrations of an electrolyte retards the ingress of water into an epoxide polymer, and reduces the disruptive effect of water on aluminium‐epoxide j

ISSN:0007-1641    

DOI:10.1002/pi.4980020201

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractA number of halogenated flame retardants have been heated alone and with antimony trioxide at temperatures between 300 and 500°. Isothermal weight losses over various time periods have been followed. Quantitative analyses of reaction products from heating together both Cereclor 70/Sb2O3and also PVC/Sb2O3have shown antimony trichloride to be the main reaction product in each case

ISSN:0007-1641    

DOI:10.1002/pi.4980020202

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe angular dependence of scattered light,P(X), from randomly branched homopolycondensates was calculated by using moment‐generating functions. Analytical expressions could be derived both for Gaussian sub‐chains and for sub‐chains obeying random flight statistics. For smallXvalues (region of scattered visible light),P(X)can be well approximated by Zimm's formula:\documentclass{article}\pagestyle{empty}\begin{document}$ \overline {P_z \left( \theta \right)}^{_ - 1}= 1 + \frac{{16\pi ^2 }} {3}\frac{{ z}} {{\lambda ^2 }}\sin ^2 {\theta \mathord{\left/ {\vphantom {\theta 2}} \right. \kern-\nulldelimiterspace} 2} $\end{document}which holds for linear (f= 2) and branched polycondensates as well. At largeXvalues (X‐ray small angle scattering), however, strong deviations from the linear Zimm formula appear. The effect of excluded volume alters the mean‐square radius of gyration but has no detectable influence on the shape of the particle scatteri

ISSN:0007-1641    

DOI:10.1002/pi.4980020203

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe emulsion polymerisation of styrene, using sodium dodecanoate as emulsifier and hydrogen peroxide as initiator, has been used to prepare a series of polystyrene latices of different sizes. The size range covered was from 600 Å to 4230 Å. After removal of the soap by dialysis, the surface groups on the particles were characterised by electrophoresis. The main surface groupings were found to be carboxyl groups. Number‐average molecular weight determinations were carried out using osmometry and it was found that the molecular weight decreased as the particle size increased. The evidence obtained suggests that the growth of a latex particle involves a surface‐phase polymeris

ISSN:0007-1641    

DOI:10.1002/pi.4980020204

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractSolute electrolyte and adsorbed emulsifier can be removed by ion exchange from polystyrene latices prepared with persulphate initiator. Rigorous purification of the ion‐exchange resins is necessary to avoid contamination by leached polyelectrolytes. These ion‐exchanged latices are stabilised by strong acid surface groups ‐ sulphate end‐groups of the polymer molecules. The number of surface groups as determined by conductometric titration of the latex, plus the number buried within the particle as determined by conductometric titration of the polymer in solution (or byX‐ray fluorescence), is less than the expected value of two per polymer molecule. The other end‐groups are shown to be hydroxyl groups by oxidation to the carboxyl form followed by ion exchange and titration. The total number of end‐groups thus determined is close to two per molecule. As the pH of the polymerisation medium is decreased, the proportion of hydroxyl end‐groups increases and that of the sulphate end‐groups decreases. No carboxyl groups are detected in ion‐exchanged latices prepared in a nitrogen atmosphere, independent of the nature of the emulsifier. The dye partition method gives end‐group concentrations that are far lower than those determined by titration orX‐ray fluorescence, probably because the formation of the dye end‐group ion‐pair is not complete. Finally, for latices prepared at relatively low emulsifier concentrations, the contribution of the sulphate end‐groups to the surface charge density is significant and cannot be overlooked,

ISSN:0007-1641    

DOI:10.1002/pi.4980020205

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe effects of content and sequence distribution of residual acetyl groups in the polymer chain, and carbonyl content of polyvinyl alcohol, on the emulsion polymerisation of vinyl acetate in the presence of polyvinyl alcohol were investigated.Properties of modified polyvinyl alcohol grades as a protective colloid were also studied.Results show that the viscosity, particle size, stability and the freeze‐thaw stability of the emulsion are determined largely by the fine chemical structure of the polyvinyl alcohol used in the polymerisatio

ISSN:0007-1641    

DOI:10.1002/pi.4980020206

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractPolyvinyl acetate (PV‐OAc) emulsions made from vinylacetate (V‐OAc), using polyvinylalcohol(PV‐OH) as the protective colloid, have different viscosities depending on the degree of interaction between the aqueous solution of V‐OAc and PV‐OH. This interaction increased when the PV‐OH samples, prepared by addition of various amounts of benzene to a methanolic solution of PV‐OAc, had a higher content of residual acetyl groups with a more blocklike distribution. The mechanism of heterogeneous distribution of residual acetyl groups in PV‐OH and effect of branching of PV‐OH on the PV‐OAc emulsion

ISSN:0007-1641    

DOI:10.1002/pi.4980020207

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe ability of low molecular weight acrylic acid copolymers to form self‐dispersions of a maximum polymer content at partial, rather than complete, neutralisation has been qualitatively explained in terms of swelling of the particles with water. Studies on copolymers containing groups capable of strong interaction, such as amide or hydroxyl, combined with the tendencies of monolayers of related polymers to contract at particular pH values has suggested that an ion/polar group type of interaction is responsible for the decreased volume of the particles at the pH of maximum polymer conten

ISSN:0007-1641    

DOI:10.1002/pi.4980020208

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractThe properties of polymer emulsions are described in which styrene is copolymerised with a range of acrylic esters, together with a minor quantity of acrylic acid. Properties examined included viscosity and minimum temperature of film formation of the emulsions, and the brittle point, rigidity modulus, tensile strength at maximum elongation, and elongation of the air‐dried films. The increase in chain length of the alkyl ester and the quantity of acrylate comonomer both gave more flexible and softer polymers. While approximately equivalent properties may be obtained by replacing one acrylate comonomer by an appropriate quantity of another, each copolymer is unique in its combination of propertie

ISSN:0007-1641    

DOI:10.1002/pi.4980020209

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY

摘要:

AbstractIn the packaging industry increase of machine speeds requires adhesives with faster setting speeds. A range of polyvinyl acetate homopolymers and copolymers has been examined on a standard paper under a standard breaking load. For the polymers examined, setting speed was increased by the use of polyvinyl alcohol as stabiliser in preference to other colloids or surfactants, by addition of polyvinyl alcohol, by copolymerisation with ‘soft’ monomers and by addition of solvent. Setting speeds were decreased by reducing the solids content, particularly below 45%, and by incorporation of inorganic fillers.Theories to explain these results are propo

ISSN:0007-1641    

DOI:10.1002/pi.4980020210

出版商:John Wiley&Sons, Ltd    

年代:1970

数据来源: WILEY