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  • 1
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric constant of a crosslinked sheet of Viton was measured at two frequencies, 200 cycles/sec. and 100 kcycles/sec., for various elongations. The difference (∊s - ∊∞) decreased sharply when the sample was strained and then increased slowly during stress relaxation. Relaxation was slow at the temperature of these measurements (35°C.), so that we were only able to estimate the behavior at long time for the lowest elongations. Even under these conditions it was possible to demonstrate that the (∊s - ∊∞) values corresponding to long times decrease with elongation. The root mean square dipole moments for a C5F8H2 group are estimated from these data by both a modified form of the Onsager relation and the more recent treatment of Harris and Alder. Stress relaxation and birefringence measurements were performed with elongation and temperature as variables. Viton exhibits linear viscoelastic behavior up to an elongation a of 1.5. The isothermal data indicate a linear relationship between birefringence and stress, both during stress relaxation and recovery. The streas-optical coefficient, C, is 2.35 × 10-4 cm.2/kg. at 28°C. Master curves could be constructed from both the reduced stress and birefringence data a t different temperatures for the same shift factors, aT. The apparent activation energy i s 56 kcal./mole and the characteristic temperature in the simplified WLF equation is TS, = 336 ± 5°C. The birefringence as measured under essentially equilibrium conditions at α = 1.23 was independent of temperature in the range 30-70°C.; however, the CT product measured during relaxation increased from 7 × 10-2 to 8.8 × 10-2 in the same temperature interval. The data were insufficient to determine whether this departure from Gaussian behavior arose from the time dependence or represented an equilibrium effect.
    Additional Material: 11 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two cases of initiation of vinyl polymerization by radical-ions are considered. In the one case the transfer from radical-ion to monomer is instantaneous and virtually complete. Here the relative amount of free radical propagation as compared to anionic propagation is negligibly small. In the second case a continuous feed of radical-ion initiator is considered. Here the relative amount of free radical propagation as compared to anionic propagation may be considereable. Exact expressions are developed for this relative radical versus ionic propagation as a function of conversion. It is suggested that the results of lithium-initiated copolymerization of methyl methacrylate and styrene may be understood in terms of a model similar to the second case of radical-ion initiation considered in this paper.
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  • 3
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Interaction of water with connective tissue is an important biophysical process. The chemical and physical morphology of tendons is a complex syncitium of collagen (procollagen + collastromin), mucopolysaccharide (aqueous phase + dense phase), and water (free and bound). It is proposed that a kinetic analysis of swelling of tendons might add new facts concerning the properties of the above tissue system. The present study shows that although diffusion may be the transport basis for swelling, there exists an anomalous dependence of diffusion on time of swelling. It is proposed that the velocity of swelling (dW/dt) is equal to a term Ks(A/W - BW), the latter embodying a specific rate constant Ks, a driving factor A, and a retardation factor B which relates transitory tendon weight W to the initial weight W0, the equilibrium weight W∞ and time t. When this equation is integrated, a working expression is obtained that agrees satisfactorily with experimental data. It is supported further by theories of swelling of anisotropic gels. Data plotted in the form of log (W2∞ - W2)/(W2∞ - W20) versus t showed good agreement with linearity required by the above rate equation. Longitudinal stress decreased swelling ratio W∞/W0, but sped up attainment of equilibrium.
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  • 4
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Evidence is offered which confirms, and in some cases, changes previously suggested assignments of bands in the spectra of Hevea and balata. In particular it is shown that bands at 764 (13.1 μ) and 742 cm.-1 (13.5 μ) are probably connected with vibrations of the cis- or trans-C (CH3)=CH— group, a band at 11.30 cm.-1 (8.85 μ) is due to a C—CH3 vibration of the cis-C(CH3)=CH group, a band at 1155 cm.-1 (8.68 μ) is due to the C—CH3 vibration of the trans-C(CH3)=CH group. Likewise the bands at 1315 (7.60 μ) and 1325 cm.-1 (7.55 μ) are probably due to a CH vibration of the cis- and trans-C(CH3)=CH groups, respectively. The 1130-cm.-1 band and the 1155-cm.-1 band are found in spectra of polydimethylbutadiene and thus are probably group frequencies. The 1315 and 1325-cm.-1 bands (shifted) are also found in polybutadiene and polypiperylene spectra and thus are probably group frequencies also. It is also shown that the 890-, 1645-, and 3077-cm.-1 bands are best explained by the presence of an isopropenyl, CH2=C(CH3)— group. These assignments are based on a study of the polarization spectra, the spectra of maleic anhydride adducts and hydrogenated polyisoprenes, and on microstructure determinations.
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  • 5
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Assignments are suggested for many bands in the spectra of various kinds of polybutadienes which either confirm those deduced from olefin spectra or are new. In particular the band at 1355 cm.-1 (7.38 μ) is probably due to trans-CH=CH, that at 1311 cm.-1 (7.63 μ) is due to cis-CH=CH as is a band at 740 cm.-1 (13.5 μ). These assignments are based on the study of polarization spectra, of the spectra of hydrogenated polybutadienes and maleic anhydride adducts of polybutadienes and on isomerization experiments of cis-1,4-polybutadienes. Evidence is offered which indicates that presently known high cis-1,4-polybutadienes are not simply butadiene polymerized by cis-1,4 addition and that probably other structures are present in the polymer. It is shown that the 1355- and 1311-cm.-1 bands appear in the spectra of polypiperylenes and polyisoprenes (shifted somewhat in the latter spectra) and consequently are due to a CH vibration of the trans- or cis-CH=CH group. Thus they are group frequencies.
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  • 6
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The formation and melting of the two crystalline modifications of poly-1-butene have been studied by the techniques of differential thermal analysis, infrared spectroscopy, dilatometry, and polarizing microscopy. On cooling the melt, modification 2 (Tm = 120-126°C.) appears within minutes. This form is unstable and gradually transforms to modification 1 (Tm = 135-142°C.). A density change of over 4% accompanies this latter transformation. As torsional damping experiments have shown the amorphous content to decrease by only about 5%, the stable modification must be much more dense than the unstable form. The kinetics of the crystallization of modification 2 from the melt were studied primarily dilatometrically at several temperatures. The data generally followed the Avrami equation with n equal to 4. This crystallization shows a high negative temperature coefficient (T1/2 = 380 min. at 110°C. and 2 min. at 90°C.) and becomes too rapid to measure by this technique at lower temperatures. The kinetics of the transformation of modification 2 to modification 1 were followed in infrared spectral, density gradient tube, and dilatometric studies. At room temperature, halftimes ranging from 250 to 1600 min. were observed, depending on the mechanical and thermal history of the sample. The observed discrepancies have been shown to be due, at least in part, to orientation effects. In dilatometric studies of the temperature dependence, the transition rate showed a pronounced maximum in the region of 15°C. Large increases in the torsional modulus and offset yield point of the specimen were observed to accompany the transition.
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  • 7
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular weight distribution of high density polyethylene and polymethylene has been measured by analysis of sedimentation velocity experiments carried out at high temperatures. The solvent, α-bromonaphthalene, produced less sensitivity of flotation to molecular weight than could be expected for a highly desirable but presently impossible θ-solvent. The molecular weight distributions obtained by this method are compared with those obtained by solution precipitation fractionation procedures.
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  • 8
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A study of the nature and quantity of materials that will react with dibutylzinc to act as cocatalysts for the polymerization of phenyl glycidyl ether has led to the finding of several very effective catalyst systems. These cocatalysts may be grouped in the following classifications: (1) highly effective: water and acetone; (2) effective: methanol, ethanol, n-butanol, and oxygen; (3) slightly effective: isopropancl, tert-butanol, diethylamine, n-butyraldehyde, and phenol; and (4) inhibitors: acetic acid, ethyl acetate, and carbon dioxide. The poly(phenyl glycidyl ether) produced by these catalysts is a high melting (204°C.), high molecular weight crystalline polymer which is insoluble in most common organic solvents. Ethylene oxide and propylene oxide have also been polymerized by the dibutylzinc-water system to high molecular weight polymers in high yield. Epichlorohydrin, on the other hand, gave only low molecular weight oils in low yields, probably due to reaction of the catalyst species with the reactive chlorine of the monomer.
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crosslinked phenol sulfonic acid resins in the form of rods have been prepared. Anion uptake by these resins in equilibrium with aqueous solutions of NaCl, NaBr, Na2CO3, and Na3C6H5O7 at 30°C. in the concentration range 0.001-3.0N, their density, water content, and exchange capacity have been determined. From these data, activity coefficients of small ions in the resin phase have been calculated and compared with the values derived by the existing theories of Mackie and Meares, and Lazare et al. The agreement between the observed and calculated values is not satisfactory.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Copolymerization of α-pyrrolidone and ∊-caprolactam has been carried out in the presence of sodium and acetyl compounds. A large amount of both catalysts is necessary to obtain a comparatively good yield. Infrared absorption measurement was adopted to obtain the polymer composition. The compositions of unreacting monomer were determined by equation: D958/D994 = 0.501(CclCpy), where D958 and D994 are optical densities at 958 and 994 cm.-1, which are characteristic absorptions of ∊-caprolactam and α-pyrrolidone, respectively, and Ccl and Cpy, are concentrations of monomers in weight. The polymer composition was calculated from this composition of residual monomers. The polymerization was followed by this analysis and it was found that the α-pyrrolidone polymerized a t the early stage of reaction while ∊-caprolactam reacts with a steady rate. Higher temperature made this phenomenon distinguishable and the degradation of α-pyrrolidone was observed. The optimum temperature for polymerization was 90-110°C. The stability of α-pyrrolidone anion explains these phenomena, as this anion promotes alkaline-salt formation and degradation and reduces the chain numbers. The prepared copolymers have low melting points and good solubilities which vary according to composition. The melting point of the copolymer whose composition is 1 mole caprolactam: 1 mole pyrrolidone is as low as 140°C. and this polymer shows good solubility in ethanol. Apparent monomer reactivity ratios indicate that the copolymers formed are block copolymers.
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