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  • 1
    Electronic Resource
    Electronic Resource
    Thermal expansion of crosslinked closed-cell polyethylene foams (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2587-2596 
    Details
    ISSN: 0887-6266
    Keywords: polyolefin foams ; thermal properties ; closed-cell foams ; linear thermal expansion coefficient ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An experimental study on the thermal expansion of a collection of crosslinked low-density polyethylene (LDPE) foams with closed-cell structure is presented. The thermal characterization of these materials, the relationships between the linear thermal expansion coefficient and the structure of the foams, and the determination of the variables that can modify the thermal properties of these products are the goals of this work. The experimental results show that the linear thermal expansion coefficient decreases when the density of the foamed material increases. The gas expansion inside the cells is a mechanism that should be taken into account. Moreover, the thermal expansion also depends on the cellular structure. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2587-2596, 1998
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oligomérisation anionique de l'ethylène. I. Etude cinétique (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 875-895 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic study of ethylene oligomerization in hexane, in the presence of n-BuLi-TMEDA complexes, allowed us to suggest a new mechanism for anionic ethylene oligomerization. n-BuLi and n-Bu(CH2CH2)Li species have the same reactivity. The RLi-TMEDA complex in a 1-to-1 stoichiometry is the active species. The following kinetic equation has been established: \documentclass{article}\pagestyle{empty}\begin{document}$$ V_p = k_p K_D ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} \left[ {\left( {{\rm BuLi} - {\rm TMEDA}} \right)_2 ^{{1 \mathord{\left/ {\vphantom {1 2}} \right. \kern-\nulldelimiterspace} 2}} } \right]\left[ {{\rm Et}} \right] $$\end{document} It reflects the intervention of associated species (n-BuLi-TMEDA)2 as well as the influence of the concentration of the complexing agent on the kinetics of oligomerization.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150410
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  • 3
    Electronic Resource
    Electronic Resource
    Radical polymerization in the presence of complexing agents. VI. Effect of low concentrations of ZnCl2 on the overall rate of copolymerization of methyl methacrylate with ethyl acrylate (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 2749-2754 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Overall rates for the free-radical copolymerization of methyl methacrylate with ethyl acrylate in the presence of low concentrations of ZnCl2 have been determined at 50°C. The rate of copolymerization Rp depends on both the ZnCl2 concentration and the monomer feed composition. Relative copolymerization rates Rp/R0p where R0p is the rate of copolymerization in the absence of complexing agent in the reaction mixture, show a minimum for intermediate feed compositions, independently of the ZnCl2 concentration. On the basis of the results obtained, a conventional copolymerization mechanism is proposed for this system in which free and complexed species of both acrylic monomers participate.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.170210912
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  • 4
    Electronic Resource
    Electronic Resource
    Oligomerization of ethylene by tertiary butyllithium-N,N,N′,N′-tetramethylethylenediamine (TMEDA) (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 14 (1976), S. 773-776 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.170140325
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  • 5
    Electronic Resource
    Electronic Resource
    Oligomérisation anionique de l'ethylène. II. Etude des paramètres thermodynamiques (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 897-900 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic study, as a function of temperature, of ethylene oligomerization by the n-BuLi-TMEDA complex allowed us to evaluate the thermodynamic parameters (ΔS
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150411
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  • 6
    Electronic Resource
    Electronic Resource
    Oligomérisation anionique de l'ethylène. III. Application à la synthèse d'alcools à longue chaine (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 15 (1977), S. 901-912 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Living oligomers of ethylene obtained by n-BuLi complexed with TMEDA have been deactivated by ethylene oxide. The nuclear magnetic resonance study of the product obtained allowed us to follow the influence of TMEDA toward the functionalization. Three products have been characterized: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm Bu}\hbox{---} \left( {{\rm CH}_2 \hbox{---} {\rm CH}_2 } \right)_{\rm m} \hskip-3pt\hbox{---} {\rm CH}_{\rm 2} \hbox{---} {\rm CH}_{\rm 2} \hbox{---} {\rm OH}} \\ {{\rm Bu}\hbox{---} \left( {{\rm CH}_2 \hbox{---} {\rm CH}_2 } \right)_{\rm n} \hskip-3pt\hbox{---} {\rm CH}\hbox{=\hskip-1.5pt=} {\rm CH}_{\rm 2} } \\ {{\rm Bu}\hbox{---} \left( {{\rm CH}_2 \hbox{---} {\rm CH}_2 } \right)_{\rm p} \hskip-3pt\hbox{---} {\rm CH}_{\rm 2} \hbox{---} {\rm CH}_{\rm 3} } \\ \end{array} $$\end{document} By increasing the ratio [TMEDA]/[n-BuLi] one obtains a decrease of the functionalization reaction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.170150412
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  • 7
    Electronic Resource
    Electronic Resource
    Radical polymerization in the presence of complexing agents. V. Effect of low concentration of ZnCl2 on the radical copolymerization of methyl methacrylate with ethyl acrylate (1983)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 21 (1983), S. 2739-2748 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactivity ratios for the free-radical copolymerization of methyl methacrylate with ethyl acrylate in the presence of low concentrations of ZnCl2 are analyzed at different polymerization temperatures, 35,50, and 65°C. The different tendencies of the two monomers toward the formation of molecular complexes with the metal halide modify the homopropagation and cross-propagation coefficients and the results obtained seem to indicate a conventional cross-propagation mechanism in which both free and complexed species of acrylic monomers participate.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1983.170210911
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  • 8
    Electronic Resource
    Electronic Resource
    Structural studies on the polymorphism of nylon 3 (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 23 (1985), S. 733-742 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The structure and morphology of crystalline nylon 3 [poly(β-alanine)] have been studied by electron microscopy and x-ray diffraction. Two clearly defined forms are detected. Form I appears as spherulites made up of ribbonlike lamellae upon crystallization at high temperature from a solution in phenol-butanediol-1,4. They have monoclinic unit cell with a = 9.60 Å, c = 8.96 Å, and β = 122.5°. The hydrogen-bonded planes run parallel to the long dimension of the crystals. Form II is observed when the samples are prepared from formic acid solution at room temperature. A second type of spherulite with a microfibrillar structure is formed in this case. The isolated crystalline structures obtained from Form II appear to grow along the intersheet direction rather than along the hydrogen bond direction, which constitutes anomalous behaviour. Our results for this second form are consistent with an orthorhombic lattice with a = 9.56 Å and c = 7.56 Å. No clear information is obtained on the b dimension of the unit cell (chain axis) in either case. We assume a value of 4.78 Å, which corresponds to fully extended chains. The two forms coexist in films prepared from a formic acid-water solution as well as in samples recovered immediately after polymerization.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.180230409
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  • 9
    Electronic Resource
    Electronic Resource
    Triple melting behavior of poly(ethylene terephthalate co-1,4-cyclohexylene dimethylene terephthalate) random copolyesters (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 763-781 
    Details
    ISSN: 0887-6266
    Keywords: random copolyesters ; copolymers ; crystallization ; melting ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melting behavior of poly(ethylene terephthalate co-1,4-cyclohexylene dimethylene terephthalate) [PET/CT] random copolyesters has been studied. The basis of this analysis was the triple melting behavior of PET homopolymers, which is commonly observed after a period of isothermal crystallization followed by linear heating in a differential scanning calorimeter. Both ET and CT homopolymers are able to crystallize, and as a consequence, the copolymer morphology depends on the ET/CT ratio. It has been reported that at low CT concentrations, the ET units can crystallize with complete rejection of the CT units and that at high CT concentrations, the CT units can cocrystallize with the ET units. In the present work, low CT concentrations were selected, as they are completely rejected from the ET crystals. The purpose was to further test the hypothesis that in the triple melting behavior of PET homopolymers, the second DSC melting endotherm is related to secondary species crystallized by material rejected from the primary crystals. This concept arose from our previous work, where it was speculated that increasing the average molecular-weight of PET would enhance molecular entanglement and increase secondary crystallization. This process would give rise to a higher amount of species being rejected from the main crystals, i.e., an increase of secondary crystallization would occur, and as a consequence the second melting endotherm would be enhanced. Similar to the effect of molecular weight, such behavior has been observed as a function of rejected copolymer content. This gives support to our previously proposed step-like crystallization and melting mechanism for PET homopolymers, and has the potential to be extended to other high temperature semicrystalline polymeric systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 763-781, 1998
    Additional Material: 26 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    The triple melting behavior of poly(ethylene terephthalate): Molecular weight effects (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1757-1774 
    Details
    ISSN: 0887-6266
    Keywords: polyesters ; crystallization ; melting ; morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melting behavior of isothermally crystallized PET has been studied using linear heating in a differential scanning calorimeter (DSC). Variables such as crystallization temperature, crystallization time, heating rate, and average molecular weight are the main focus of the study. On the basis of several experimental techniques, a correlation of the melting behavior of PET with the amount of secondary crystallization was found to exist. It was observed that the triple melting of PET is a function of programmable DSC variables such as crystallization temperature, crystallization time, and heating rate. However, in testing the hypothesis that there was a correlation between melting endotherms and secondary crystallization inside spherulites, it was found necessary to use a DSC-independent variable in order to enhance the observed effects. Therefore, on the basis of a crystallization model that involves secondary branching along the edges of parent lamellar structures, it was speculated that an increase in the average molecular weight could affect the triple melting of PET due to an increase of rejected portions of the macromolecules. It was found that the second melting endotherm increased, apparently, at the expense of the third one as the average molecular weight was increased. The second melting endotherm was also found to correlate proportionally with the amount of secondary crystallization inside spherulites. The results support a model of crystallization which basically consists of parent crystals and at least one population of secondary, probably metastable, crystals. This latter structural component must involve excluded portions of the macromolecules that did not crystallize during the isothermal crystallization period of the parent crystals. An increase of molecular weight gives rise to a higher entanglement density which in turn increases the fraction of initially rejected chain sections and therefore the amount of secondary crystallization. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1757-1774, 1997
    Additional Material: 17 Ill.
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