摘要:

AbstractSemiefficient vulcanization systems (semi‐EV) are often used when a stock requires good aging properties as well as good fatigue resistance. A partial replacement of sulfur in a conventional cure system with 4,4′‐dithiobismorpholine or 2‐mercaptabenzothiazyl 4‐morpholino disulfide (BMD) is an example of semi‐EV system. However, with BMD the scorch time is not always long enough for multisteps involved in the manufacturing of tires. Such new cure retarders asN‐(cyclohexylthio)phalimide orN, N′‐bis(cyclohexylthio)oxanilide showed very little efficiency in BMD cure systems. This paper describes the usage of new curing agents, (N‐morpholinothio)imides, which can overcome the disadvantage of scorchness in BMD cure system and provide excellent aging properties. This is rationalized by the formation of BMD during vulcanization. The facile formation of BMD fromN‐(4‐morpholinothio)phthalimide (MTP) and 2‐mercaptobenzothiazole (MBT) serves to illustrate the feasibility ofin situformation of BMD during cure and to explain long scorch time observed withN

ISSN:0021-8995    

DOI:10.1002/app.1977.070210701

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractThe distribution of HAF carbon black in SBR was studied with the electron microscope and Fraunhofer diffraction. The interparticle distance between black aggregates is 8000 Å at 20 phr and 7000 Å at 40 phr, but above 60 phr it spreads broadly in the vicinity of 4000 Å. The size of black aggregates at 20 phr extends from 300 Å to 3000 Å, and the average diameter is 1200 Å. At 40 phr and 60 phr, black trends to aggregate more than at 20 phr and the average diameter is about 1500–1600 Å; the maximum diameter exceeds 5000 Å. In a black aggregate, there are about 40 spherical particles independently of filler concentration. From the relation between the size and interparticle distance, the connection of black aggregates initiates at 40 phr level and affects the physical properties of fill

ISSN:0021-8995    

DOI:10.1002/app.1977.070210702

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractVinyl acetate was batch polymerized at 60°C int‐butanol solution. Conversion and molecular weights were measured as functions of time for several initiator and solvent concentrations. Although the overall rate constant depends somewhat on solvent concentration, the reaction is first order in monomer concentration up to at least 60% conversion and one‐half order in the concentration of initiator. Molecular weights were independent of initiator concentration, confirming that the polymerization is transfer dominated. Measurements of M̄wand M̄wversus conversion were used to establish the individual transfer constants. All are independent of solvent concentration, exceptCp, the polymer transfer constant, which decreases systematically with increasing solvent concent

ISSN:0021-8995    

DOI:10.1002/app.1977.070210703

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractTransparent crosslinked PVA hydrogels were prepared by electron beam irradiation of aqueous solutions under nitrogen. These weak hydrogels, upon swelling at 30°C in water, showed low elastic moduli (up to 50 psi), low ultimate tensile strength (up to 4 psi), and low extensibility to break (not higher than 85%). Values of the molecular weight between crosslinksMcwere calculated from swelling and from tensile experiments. In fact, two values ofMcwere calculated for each swelling experiment, (a) allowing for observed variation in the polymer–solvent interaction parameter χ1with concentration, and (b) fixing χ1= 0.494 according to literature data. The correlation of theMcobtained from tensile data with theMcobtained from swelling data, by (a) or (b), was approximately linear and gave the same per cent agree

ISSN:0021-8995    

DOI:10.1002/app.1977.070210704

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractThe vulcanization of butyl rubber byp‐quinone dioxime oxidized by red lead and tetrachloroquinone was investigated. The maximum physical effective crosslinking density of the vulcanizates appeared to be whenp‐quinone dioxime and the oxidizing agent were equimolar. The formation of one physical effective crosslink required one molecule ofp‐quinone dioxime. Chemical reactions are suggested for the vulcanization

ISSN:0021-8995    

DOI:10.1002/app.1977.070210705

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractChlorobisphenolic epoxy resins in crystalline form, e.g., bisglycidyl ether of 2,2‐bis(p‐hydroxyphenyl)‐1,1,1‐trichloroethane (BGECBP) and the system sulfur–N‐cyclohexyl‐2‐benzothiazolesulfonamide were used as crosslinking agents for vulcanization of butadiene–styrene and butadiene–acrylonitrile rubber. The density of crosslinking was determined by the equilibrium swelling method and on the basis of the Mooney‐Rivlin equation which gives the relation between stress and elongation. The dynamic properties, namely,G′ andG″ and mechanical loss factor δ, were determined. On the basis of these results, mechanisms for the crosslinking reaction were advanced, the activation energy was determined, and comparisons between crosslinking rates by different systems were made. It was found that vulcanizates crosslinked by BGECBP possess higher heat aging resistance and lower glass transition temperatures in comparison with those crosslinked by means of sulfur in the presence ofN‐cyclohexy

ISSN:0021-8995    

DOI:10.1002/app.1977.070210706

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractThe rejection of calcium and/or magnesium ion by asymmetric cellulose acetate hyperfiltration membranes is increased significantly by formation of the corresponding alkaline‐earth metal chelate. Typically solute fluxes are reduced by a factor of 5 consequent to chelation with ethylenediaminetetraacetic acid (EDTA) at pH 6.0. Selective chelation and, in turn, selective transport of magnesium is observed when equimolar solute mixtures corresponding to 1:1:1 magnesium:calcium:EDTA are hyperfiltered. Under these conditions, calcium successfully competes for the stoichiometrically limiting EDTA, and the rejection of magnesium is lower than the rejection observed for the hyperfiltration of the MgEDTA2−complex in the absence of competitive calcium. Alternatively, the rejection of the CaEDTA2−complex is increased under these identical conditions, presumably as a consequence of specific interactions between the available free magnesium and the cellulose acetate membrane. The effects reported here all seem to be related to reductions in solute diffusivity associated with the increased size of the alkaline‐earth metal ion

ISSN:0021-8995    

DOI:10.1002/app.1977.070210707

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractVolume resistivity, dielectric strength, dielectric constant, and loss tangent of unsaturated polyester resins and their GRP were studied as a function of the bromine content of the resin. The bromine was introduced by using bromostyrene as the crosslinking monomer. Bromine content was established by partial or total replacement of the styrene. Also, the effects of short and long water‐boil treatments on these properties were investigated. The electrical and dielectrical properties were shown to be independent of the bromine content of the resi

ISSN:0021-8995    

DOI:10.1002/app.1977.070210708

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractApplication of Rayleigh spectroscopy for characterization of particle size in nonaqueous dispersion and water‐based emulsion paint resins is described. The technique allows a straightforward and rapid estimation of particle size; the measurement does not require exact determination of scatterer concentration. For monodisperse samples, unambiguous results are obtained for particles at least up to 50 μm in diameter; for polydisperse samples, an average size heavily weighted by large particles is obtained. Typical experimental results on monodisperse and polydisperse water‐based latexes and on polydisperse nonaqueous dispersion resins are described. In the latter case, comparison of electron micrograph and light scattering size determinations indicates that the light scattering experiment yields approximately az‐average radius. Observations on particle formation and growth during polymerization are also des

ISSN:0021-8995    

DOI:10.1002/app.1977.070210709

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractThe elongational flow behavior of dilute polymer solutions is of great current interest because it has been suggested that elongational viscosity effects may be involved in a number of phenomena such as turbulent drag reduction and flow cavitation suppression. Unfortunately, recent experiments, in trying to investigate elongational effects, have produced widely varying results. In this paper, an attempt is made to analyze one of the factors that contribute to this diversity. By using a generalized convected Maxwell model, it is shown that in a transient elongational flow, both stretching rate and flow time must reach the proper values before high stress levels can be observed. This is true for both accelerating flows such as through a cone or wedge and decelerating flows such as in a free jet. Since most previous experiments have not considered flow time, consistent results cannot be expected. Consequently, the proper control of all flow conditions is an essential requirement when trying to observe high stress levels. The results presented here provide valuable guidelines in this regard.

ISSN:0021-8995    

DOI:10.1002/app.1977.070210710

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY