ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Physics  (430)
  • 1965-1969  (430)
  • 1955-1959
  • 1945-1949
  • 1967  (430)
  • 11
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 663-670 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Current network theory exhibits inconsistencies which show up particularly clearly in deformation of networks prepared by crosslinking a polymer in solution. A check of theory can be obtained if one knows precisely the number of crosslinks in the network and if a range of deformations is applied to the network. In an effort to explore this problem we have examined the relation of shear modulus to crosslink density, primary molecular weight, and polymer concentration for a series of poly(vinyl alcohol) gels at low to intermediate concentrations. Aqueous poly(vinyl alcohol) solutions were crosslinked to form infinite networks using terephthalaldehyde. We find a large discrepancy with these poly(vinyl alcohol) gels between measured shear modulus and that calculated from classical elasticity theory assuming quantitative reaction of crosslinking. The ratio of measured to calculated modulus is independent of crosslink density for a given primary molecular weight and concentration. It shows linear dependence on polymer concentration prior to crosslinking and extrapolates to a critical concentration which is consistent with the effective sizes of the polymer molecules.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 671-684 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rate of water sorption at 25°C. has been determined for a number of polyacetal films differing in structure, density, and orientation induced by extrusion. The equilibrium water uptake was found to be a linear function of density only; no other effect of structure or orientation was detectable. The extrapolated density for zero sorption was 1.51 g./cc., not far from the theoretical crystalline density. The diffusivity of water in unoriented films rose with decreasing density; for linear copolymer, the trend was parallel to that of the area under the dynamic mechanical loss peak associated with long-range chain motions in the disordered regions (β-transition). Less pronounced effects of molecular weight and long chain branching on diffusivity were also noted. Films crystallized while an extruded melt was still oriented showed considerable increases in water diffusivity, but no significant changes in the apparent activation energies of permeation (about 6.6 kcal./mole) or diffusion (about 11.5 kcal./mole). On annealing these films, the diffusivity remained almost constant while the sorption coefficient and retraction on remelting decreased.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 685-696 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The cavity model used in the theory of dielectrics was applied to hydrodynamics to calculate the force exerted by a system of soft dumbbells on a reference dumbbell in a hydrodynamic field. The influence of this force on the viscosity and flow birefringence and its dependence on both the concentration and velocity gradient were calculated. The system of equations has a real solution only for values of β = M[η]η0γ/RT which are smaller than a critical value rapidly decreasing with increasing concentration. At zero concentration the results obtained agree with the theory of a single isolated dumbbell model. The calculated Huggins constant is k′ = 0.4. The extinction angle is connected with the relative viscosity very nearly as derived from experiments. However, the theory fails at higher concentrations and gradients yielding an increase in viscosity with the gradient and infinite zero-shear viscosity for the concentration c = 2.5/[η].
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 839-852 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The present study is concerned with some network properties of polyurethane elastomers in which stability is acheived via physical crosslinkages such as microcrystallites or secondary bonding. The techniques of isothermal, thermo-, and photoelasticity have been used to gain better insight into the mechanisms which occur during the deformation of these materials. It was found that stable networks are obtained only after mechanical and thermal conditioning. The well-known stress lowering which is observed during the second deformation is manifested primarily in the entropy component of the retractive force. This implies that the stress lowering results from a reduction in the number of effective network chains and not from time-dependent effects or crystallinity changes. Depending upon the chemical structure of the material, both positive and negative energy components of the force have been found.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 875-889 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An extension of the results of a previous to higher molecular weights is made. The viscoelastic parameters ηt, Je, τm, and Em are found experimentally through stress relaxation tests. The predictions of the Rouse-Bueche (RB) theory and its modified Ferry, Landel, Williams (FLW) form concerning the molecular weight dependencies of these perameters are compared with the data. It is found that the RB and FLW predictions are not rigorously obeyed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1043-1053 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Low-angle light-scattering patterns were obtained on ionotropic gels formed by the diffusion of Ca++ into a polygalacturonate sol. Near the sol-gel boundary, diffraction patterns were obtained which indicated organized structures with repeating units of 1100, 250, and 12.5 μ. Microscopic investigations confirmed that at this gel boundary capillaries run parallel to each other and perpendicular to the direction of diffusion. The diameter of capillaries was 12 μ while their length was in the 1000 μ range. Short interconnecting capillaries were about 200-300 μ in length. Inside the gel, in the more highly crosslinked parts, a disorientation occurs during the aging process with the partial disappearance of capillaries. However, at the gel-sol and gel-semipermeable membrane boundaries, the highly organized structures remain even during prolonged aging. The kinetics of the gel formation was also investigated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1103-1118 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Data on wettability of elastomers should be considered basic to the understanding of all phases of elastomer adhesion. However, no such data in the form of critical surface tensions were available for elastomers other than polydimethylsiloxane. For this study, 18 elastomers were selected to determine the effects of functional groups, of geometrical and structural isomerisms, of copolymerization, and of the induced orientation upon wettability. Most results support the constitutive law of wettability established by Shafrin and Zisman. The effect of structural isomerisms in the form of a vinyl side group and cyclization is discussed. An equation for the calculation of critical surface tension of a copolymer or of a mixture of isomers is proposed as follows: \documentclass{article}\pagestyle{empty}\begin{document}$ \gamma _c {\rm (copolymer or mixture of isomers)} \simeq \sum\limits_1^\infty {N_i \gamma _{c_i } } $\end{document} where Ni is the mole-fraction of the individual monomer in the copolymer and \documentclass{article}\pagestyle{empty}\begin{document}$ \gamma _{c_i } $\end{document} is the critical surface tension of each homopolymer. Most elastomer adhesion studies conducted in the past were concerned with the diffusion theory of adhesion. This study further supports the conclusion on the role of diffusion and adsorption in adhesion advanced in Part I, especially with respect to the physical state of polymer at the time of application. The wettability data in this study could shed some light upon major basic mechanisms involved in elastomer reinforcement.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1119-1144 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Experimental data obtained from stress-strain curves of five different textile fibers, at a series of different, constant strain rates covering a range of 61/2 decades have been used to study two methods of nonlinear viscoelastic analysis proposed elsewhere. According to the first of these, time and strain effects are factorizable so that stress σ, strain ε and time t are related by the equation σf1(ε)/ε = f(t),. This is shown to be unsatisfactory with the present materials, but an empirical modification to σf1(ε)/ε = f2(ε) + f(t) is satisfactory. According to the second, general nonlinear viscoelastic behavior can be described by an equation which reduces to the form σ/ε = F1(t) + εF2(t) + ε2F3(t) + when applied to extension at a constant strain rate. This series is shown to be strongly divergent except at fairly small stains. In fact, if it is truncated after about three terms, which are as many as can be estimated with any significance in the present experiments, it is applicable only to strains of about 3-4% and less. Numerical techniques which enable standard statistical procedures to be used have been devised to perform the above analyses and are described in detail.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1145-1156 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The theory of rate processes has been applied by Eyring to the plastic flow of solids, but he considers only the case of simple shear. Some assumptions concerning a generalization of this theory for an arbitrary strain tensor are here proposed and discussed. The components of the deformation and the work done by the deviator of the stress during the elementary flow process are evaluated. According to these results, it can be proved that the yield condition of Huber, Hencky, and von Mises is valid when there is no hydrostatic stress. The discrepancy between the yield stresses corresponding to tensile and compressive tests is explained by the influence of the hydrostatic component and evaluated by taking account of the amount of free volume required for an elementary jump. The calculated value agrees with the experimental data. Measurements of the inclination of Lüder's bands and deformation components on poly(vinyl chloride) flat bars strained by tensile tests are in good agreement with the proposed theory.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 1317-1319 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...