摘要:

AbstractThe effect of nine derivatives of salicylanilides on the elastic properties of ultraviolet‐aged natural rubber have been investigated. The results are compared with similar blends without additives and also with reference samples containing phenyl salicylate. The compounds showed variable effects, but botho‐Cl andp‐OCH3derivatives showed remarkable effects. They both help in the thermal crosslinking. Also, natural rubber samples containing these derivatives showed remarkable stability in tensile stress, elongation, and swe

ISSN:0021-8995    

DOI:10.1002/app.1979.070230801

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

年代:1979

数据来源: WILEY

摘要:

AbstractGel permeation chromatography (GPC) calibration curves log hydrodynamic volume versus elution volumes were obtained from a series of single and mixed eluents for polystyrene on inorganic carriers. The observed calibration shifts were interpreted as a result of adsorption and partition effects on elution volumeVe. Secondary contributions to the separation mechanism can be qualitatively described by means of thermodynamic relations from liquid adsorption (LSC) and liquid partition (LLC) chromatography using the solubility parameters of the eluents. The universal calibration procedure based on the hydrodynamic volume of the coils is directly applicable only for systems in which adsorption and partition is approximately the same.

ISSN:0021-8995    

DOI:10.1002/app.1979.070230802

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe permeability of H+, Na+, insulin, and hemoglobin through porous membranes made of crosslinked poly(methacrylic acid) was investigated at different pH values on both sides of the membrane. It was shown that a change in the charge of the protein during its transport through the membrane might raise the driving force of the process so much that the permeability coefficient of the protein through the membrane would be higher than in solution. In the case reported here, the flow of the protein may be regarded as partial electrophoresis in a porous medium.

ISSN:0021-8995    

DOI:10.1002/app.1979.070230803

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

年代:1979

数据来源: WILEY

摘要:

AbstractA technique is described for producing a thick interlayer composite material composed of an epoxy resin as the matrix and an acrylic‐coated fiberglass filler. Through the use of electrostatic forces, the fibers are encapsulated with a controlled, uniform layer(s) of the rubbery acrylic polymer. This coating is then crosslinked. These fibers are subsequently placed into the epoxy matrix, whereby the interfacial properties of the composite become modified. Rapid diffusion of the resin and curing agent results in an interpenetrating network being formed at the glass‐epoxy interface. The placement of a uniform latex coating on the fiberglass surface results in improvements in the mechanical properties of the composite. Increases in damping, impact strength, and tensile properties are descri

ISSN:0021-8995    

DOI:10.1002/app.1979.070230804

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe permeability coefficients for some selected systems comprising a polymer membrane and organic vapors were measured by means of simplified methods. The aim was to evaluate the suitability of these methods for permeability determination of polymer membranes under average conditions of use. The results obtained by various methods were compared and analyzed taking into account permeation models associated with different apparatus and operation principles as well as different measuring conditions. For similar mass transfer models, permeability coefficient values of the same order and close accuracy of the measurement were obtained.

ISSN:0021-8995    

DOI:10.1002/app.1979.070230805

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

年代:1979

数据来源: WILEY

摘要:

AbstractPeroxide formed on poly(vinyl alcohol) (PVA) fiber due to hydrogen peroxide (H2O2) treatment was examined in terms of formation conditions, decomposition behavior, and function of graft initiation. By treating aqueous sodium hypochlorite‐ or periodic acid‐oxidized PVA with H2O2, formation of peroxide on the substrates was observed which was not on unoxidized PVA. The amount of peroxide increased proportionally to the carbonyl content of the sample, the level of which was higher of NaClO‐ than for HIO4‐oxidized sample. The peroxide was decomposed by warming the sample in water to separate the H2O2. The reaction was easier for the HIO4‐ than the NaClO‐oxidized sample. The structure of peroxide was assumed to be the α‐hydroxy hydroperoxide type for both NaClO‐ and HIO4‐oxidized samples, which should be distinguished in respect to the location of the group. It is inferred that the peroxide on the NaClO‐oxidized sample is situated along the chain of PVA and that the one on the HIO4‐oxidized sample is located mainly at the end of the chain. It was also observed that the peroxides formed on NaClO‐ and HIO4‐oxidized samples are capable of initiating graft copolymerization of methyl methacrylate

ISSN:0021-8995    

DOI:10.1002/app.1979.070230806

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

年代:1979

数据来源: WILEY

摘要:

AbstractIn poly(vinyl alcohol) and polyacrylamide films containing the corresponding polymer–Cu2+complexes, the reason why the films may gain surface electrical semiconductivity as high as 10−3Ω−1when treated with acetone solution of iodine was investigated. Optical and scanning electron microscope observations indicated that the coagulated polymer–Cu2+complexes favor the appearance of the high conductivity and that the state of coagulation depends on the anions of the copper salts used as well as two parameters,F1≡ [Cu2+]/[MU]andF2≡ [OH−]/[Cu2+], where [MU]is the molar concentration of monomeric units of the polymer and [OH−] is that of hydroxide ions added. The effectiveness of the anions in causing coagulation decreases in the order of SO42−>Cl−>NO3−≈ Br−. The whitish substance that appears on the film surface after the iodine treatment gives x‐ray Debye–Scherrer rings characteristic of γ‐CuI. The γ‐CuI surface layer adheres to the film rather firmly, at least in polyacrylamide, and is responsible for the conductivity. By controlling the state of coagulation of the complexes and hence the formation of the γ‐CuI surface layer, we have produced films with anisotropic surface electrical semiconductivity, i.e., σ∥≈ 10−4Ω−1and σ∥/σ⊥= 1 ˜ 103. Optical and ESR spectra are also obtained to understand the mechanism of γ‐CuI f

ISSN:0021-8995    

DOI:10.1002/app.1979.070230807

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

年代:1979

数据来源: WILEY

摘要:

AbstractAn experimental study of shear viscosity η(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}), principal normal stress differenceN1(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}), storage modulusG′(ω), dynamic viscosity η′(ω), and filament elongation to breakLBis reported for solutions of several polyamides; namely, nylon 66 in sulfuric acid (H2SO4) and formic acid (HCOOH), poly(γ‐benzyl‐L‐glutamate) (PγBLG) inm‐cresol, Nomex in H2SO4and dimethylacetamide (DMA)/5% LiCl, and Kevlar in H2SO4at 25 and 60°C. The variation of properties with concentration, polymer backbone and chain configuration, and solvent type is emphasized. The nylon 66/H2SO4solutions have higher viscosity, normal stresses, and storage modulus than the HCOOH solutions of equivalent concentrations. The Nomex/H2SO4solutions have higher viscosity and higher normal stresses and storage modulus than the DMA/LiCl solutions at equivalent concentrations. The significance of polymer chain backbone rigidity in forming liquid crystalline phases in Kevlar and PγBLG solutions is discussed and its influence on flow properties in indicated. These systems allow polarized light to pass through crossed polarizers and show maxima in viscosity–concentration data. The 25°C Kelvar solutions are distinctive in that they exhibit apparent yield stress values. This gives distinctive shear flow and oscillatory data. Filament elongation‐to‐break data show Kelvar>Nomex>nylon 66 in H2SO4solutions for

ISSN:0021-8995    

DOI:10.1002/app.1979.070230808

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

年代:1979

数据来源: WILEY

摘要:

AbstractThe present investigation deals with amorphous polystyrene crazing behavior at both the molecular and macroscopic levels. The nature of the amorphous state is considered from the perspective of statistical fluctuation theory, especially when a mechanical force field is acting on the polymer. Past crazing studies have rather fully described the phenomenological behavior. However, these studies did not generate a fundamental molecular explanation of crazing. We now suggest a molecular approach based on the density and density distribution of physical entanglements between polymer chains as a function of molecular weight. This approach permits the molecular entanglement concept and the phenomenological parameters such as stresses and temperatures associated with crazing to be related through the use of fluctuation theory. Two fundamental results are obtained and specifically demonstrated for polystyrene. First, an accurate theoretical prediction of the volume associated with microvoid formation is explicitly determined. Second, the dependence of the number of crazes on molecular weight is also shown.

ISSN:0021-8995    

DOI:10.1002/app.1979.070230809

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

年代:1979

数据来源: WILEY

摘要:

AbstractCation‐exchange resins have been synthesized through the condensation ofN‐vinylcarbazole and poly(N‐vinylcarbazole) with furfural in presence of anhydrous AlCl3and subsequent sulfonation of the condensates. The resins have been characterized in respect to their polyfunctionality, exchange capacity, and thermal stab

ISSN:0021-8995    

DOI:10.1002/app.1979.070230810

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

年代:1979

数据来源: WILEY