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  • 1
    Electronic Resource
    Electronic Resource
    Compatibilizing effect of isocyanate functional group on polyethylene terephthalate/low density polyethylene blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 447-453 
    Details
    ISSN: 0887-6266
    Keywords: polyethylene terephthalate ; low density polyethylene ; isocyanate functional group ; compatibility ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To evaluate the compatibilizing effects of isocyanate (NCO) functional group on the polyethylene terephthalate/low density polyethylene (PET/LDPE) blends, LDPE grafted with 2-hydroxyethyl methacrylate-isophorone diisocyanate (LDPE-g-HI) was prepared and blended with PET. The chemical reaction occurred during the melt blending in the PET/LDPE-g-HI blends was confirmed by the result of IR spectra. In the light of the blend morphology, the dispersions of the PET/LDPE-g-HI blends were very fine over the PET/LDPE blends. DSC thermograms indicated that PET microdispersions produced by the slow cooling of the PET/LDPE-g-HI blends were largely amorphous, with low crystallinity, due to the chemical bonding. The tensile strengths of the PET/LDPE-g-HI blends were higher than those of the PET/LDPE blends having a poor adhesion. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 447-453, 1998
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology and melting behavior of nascent ultra-high molecular weight polyethylene (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 495-517 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; DSC ; multiple melting ; nascent morphology ; polyethylene ; synchrotron ; UHMW PE ; WAXS ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The nascent morphology of UHMW PE exhibits high melting point, high crystallinity, and increased WAXS line breadth relative to samples formed by melt crystallization. Different empirical relationships between crystal size and melting point are observed for nascent and molded samples. This differentiation is removed following nitric acid treatment of the nascent flake. Solid-state annealing behavior is differentiated by several regimes. Regime I is characterized by increasing crystallite dimensions and crystallinity at low annealing temperatures. Regime II[a] and II[b] is identified by double melting in DSC scans of moldings and nascent flake, respectively. The double melting is due to partial melting with incomplete recrystallization. Regime II[a] of moldings is differentiated from Regime II[b] of flake by an increase in melting point of the higher melting endotherm. Within Regime II[b], the partial melting of the nascent structure is sensitive to the distribution of morphological stability. Regime III is initiated at annealing temperatures approaching the zero heating rate melting point, and shows melting kinetics by DSC or time-resolved WAXS using synchrotron x-ray radiation. The superheat, partially associated with Regime III behavior, is sensitive to morphological heterogeneity and annealing history. Morphological models are discussed which highlight the role of noncrystalline regions and melting kinetics on the melting behavior of nascent form crystallinity. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 495-517, 1998
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  • 3
    Electronic Resource
    Electronic Resource
    Structures for monodisperse oligoamides. A novel structure for unfolded three-amide nylon 6 and relationship with a three-amide nylon 6 6 (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2849-2863 
    Details
    ISSN: 0887-6266
    Keywords: nylon oligoamides ; new crystal structure ; morphology ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three-amide oligomers of nylon 6 and nylon 6 6 have been investigated using electron microscopy (imaging and diffraction), X-ray diffraction, and computational modeling. A new crystal structure has been discovered for the three-amide oligomer of nylon 6. This material crystallizes from chloroform/dodecane solutions into an unfolded crystal form that has progressively sheared hydrogen bonding in two directions between polar (unidirectional) chains. This structure is quite different from the usual room temperature α-phase structure of chain-folded nylon 6 crystals, in which alternatingly sheared hydrogen bonding occurs between chains of opposite polarity in only one direction. The occurrence of this new structure illustrates the extent to which progressively sheared hydrogen bonding is preferred over alternatingly sheared hydrogen bonding. Indeed, the progressive hydrogen bonding scheme occurs in the three-amide nylon 6 material even though it requires a disruption to the lowest potential energy all-trans conformation of the chain backbone, and requires all the chains in each hydrogen-bonded layer to be aligned in the same direction. We believe the presence of chain folding, which necessarily incorporates adjacent chains of opposite polarity into the crystal structure, prevents the formation of this new crystal structure in the nylon 6 polymer. In contrast, the three-amide nylon 6 6 crystal structure is analogous to the polymeric nylon 6 6 α-phase structure, found in both fibers and chain-folded crystals, and consists of progressive hydrogen-bonded sheets which stack with a progressive shear. In both structures, the molecules (≈ 3 nm in length) form smectic C-like layers with well-orchestrated stacking of 2.2 nm to form a three-dimensional crystal. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2849-2863, 1998
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  • 4
    Electronic Resource
    Electronic Resource
    Miscibility and crystallization behavior of solution-blended PEEK/PI blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2267-2274 
    Details
    ISSN: 0887-6266
    Keywords: poly(ether ether kotone) ; polyimide ; miscibility ; crystallization ; morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Miscibility and crystallization behavior of solution-blended poly(ether ether ketone)/polyimide (PEEK/PI) blends were investigated by using DSC, optical microscopy and SAXS methods. Two kinds of PIs, YS-30 and PEI-E, which consist of the same diamine but different dianhydrides, were used in this work. The experimental results show that blends of PEEK/YS-30 are miscible over the entire composition range, as all the blends of different compositions exhibit a single glass transition temperature. The crystallization of PEEK was hindered by YS-30 in PEEK/YS-30 blends, of which the dominant morphology is interlamellar. On the other hand, blends of PEEK/PEI-E are immiscible, and the effect of PEI-E on the crystallization behavior of PEEK is weak. The crystallinity of PEEK in the isothermally crystallized PEEK/YS-30 blend specimens decreases with the increase in PI content. But the crystallinity of PEEK in the annealed samples almost keeps unchanged and reaches its maximum value, which is more than 50%. The spherulitic texture of the blends depends on both the blend composition and the molecular structure of the PIs used. The more PI added, the more imperfect the crystalline structure of PEEK. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2267-2274, 1998
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamic rheo-optical characterization of uniaxially oriented polyamide 11 (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2895-2904 
    Details
    ISSN: 0887-6266
    Keywords: polyamide 11 ; dynamic rheo-optical spectra ; deformation mechanism ; thermal treatment ; hydrogen bonds ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic mechanical analysis, coupled with polarized step-scan FTIR transmission spectroscopy, has been used to monitor the submolecular motional behavior of uniaxially oriented polyamide 11. The dynamic in-phase spectra depend upon the morphology of the samples as well as on the polarization direction of the infrared radiation. The lineshape features of the dynamic in-phase spectra and their relationship to sample deformation are analyzed on the basis of changes of the internal coordinates, the reorientation movement of several functional groups, and the thickness change of the film during the stretching cycle. Dynamic infrared spectra are helpful for deconvolution of overlapping bands on the basis of their different responses to the external perturbation, which sometimes cannot be resolved well by derivative spectroscopy or curve-fitting analysis. The lineshape features have been used to follow microstructural changes after isothermal heat treatment. Near the N—H stretching frequency, two bands at 3270 cm-1 and 3200 cm-1 are resolved and analyzed in terms of Fermi resonance between the N—H stretching fundamental mode and the overtone and combination modes of the amide I and II vibrations. The dynamic response of the N—H stretching mode correlates with the modulation of hydrogen bond strength in uniaxially oriented PA-11. After thermal treatment at the highest temperature (190°C), the dynamic response in this region is mainly caused by the modulation of crystals. In amide I region, three bands at 1680 cm-1, 1648 cm-1, and 1638 cm-1 are separated and assigned to hydrogen bond-free, hydrogen-bonded amorphous, and hydrogen-bonded crystalline regions, respectively. The dynamic responses of the hydrogen-bonded regions are more sensitive to external perturbation. Two components are found in the amide II region, and the band at 3080 cm-1 is assigned to the overtone resonance of the component with perpendicular polarization. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2895-2904, 1998
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  • 6
    Electronic Resource
    Electronic Resource
    Crystallization of micelles and matrix in dilute diblock copolymer/homopolymer solutions (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2961-2970 
    Details
    ISSN: 0887-6266
    Keywords: micelle ; blends ; crystallization ; morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallization, morphology, and crystalline structure of dilute solid solutions of tetrahydrofuran-methyl methacrylate diblock copolymer (PTHF-b-PMMA) in poly(ethylene oxide) (PEO) and PTHF have been studied with differential scanning calorimetry (DSC), X-ray, and optical microscopy. This study provides a new insight into the crystallization behavior of block copolymers. For the dilute PTHF-b-PMMA/PEO system containing only 2 to 7 wt % of PTHF content, crystallization of the PTHF micellar core was detected both on cooling and on heating. Compared the crystallization of the PTHF in the dilute solutions with that in the pure copolymer, it was found that the crystallizability of the PTHF micellar core in the solution is much greater than that of the dispersed PTHF microdomain in the pure copolymer. The stronger crystallizability in the solution was presumably due to a softened PMMA corona formed in the solution of the copolymer with PEO. However, the “soft” micelles formed in the solution (meaning that the glass transition temperatures (Tg) of the micelle is lower than the Tm of the matrix phase) showed almost no effects on the spherulitic morphology of the PEO component, compared with that of the pure PEO sample. In contrast, significant effects of the micelles with a “hard” PMMA core (meaning that the Tg of the core is higher than the Tm of the PTHF homopolymer) on the nucleation, crystalline structure, and spherulitic morphology were observed for the dilute PTHF-b-PMMA/PTHF system. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2961-2970, 1998
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  • 7
    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
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  • 8
    Electronic Resource
    Electronic Resource
    Study of bundle formation during crystallization in polymer blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 873-888 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; polymer blends ; pattern formation ; numerical simulation ; syndiotactic polystyrene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The development of texture which exists in polymer spherulites grown from single phase melts containing an appreciable amount of noncrystallizable material was investigated. This texture generally consists of lamellar bundles separated by amorphous regions, both of which are typically 0.1-1 μm thick. A space-time finite element model previously developed by us was used to simulate the growth of a group of polymer lamellae. The model determines the impurity concentration field in the melt surrounding the growing lamellae and tracks the growth of each lamella. Important variables are the initial melt concentration of noncrystallizable material, the mass diffusion coefficient of noncrystallizable species, lamellar thickness, long period, and the rate of molecular attachment at the growth front. Under certain conditions, bundles did indeed develop during the simulations. These results were used to predict bundle thicknesses. The predictions of bundle texture were compared to actual textures observed in blends of syndiotactic and atactic polystyrene. It was found both experimentally and numerically that bundle thickness was a strong function of crystallization temperature and a relatively weak function of both the initial composition of noncrystallizable species and the degree of crystallinity of the lamellar stack. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 873-888, 1998
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  • 9
    Electronic Resource
    Electronic Resource
    Analysis of crystallization kinetics of poly(ether ether ketone) (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1335-1348 
    Details
    ISSN: 0887-6266
    Keywords: PEEK ; growth rate ; crystallization ; kinetics ; regime ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An optical microscope equipped with a video photograph system was used to follow the growth of spherulites. Under nitrogen atmosphere, the growth rates at 290 and 300°C suggest that when the melt of PEEK has been equilibrated for 15 min at 400°C, the subsequent crystallization behavior was nearly independent of the prior thermal history. Linear growth rates of crystallization of PEEK have been measuredin the temperature range of 260-325°C for melt-pressed films and solvent cast films. Detailed kinetic analysis indicated that PEEK exhibited an unmistakable regime II → III transition at 296 ± 1°C. The II → III transition was clearly present irrespective of the rather drastic changes in U*. It is interesting that the branching and crosslinking retarded the growth rate of PEEK, but a transition from regime II to regime III still existed. For melt-pressed films after equilibration at 400°C for 15 min, values of σ and q suggest that U* should be taken nearer to 1500 cal/mol in the case of T∞ = Tg - 30 K and 2000 cal/mol in the case of T∞ = Tg - 51.6 K. The Kg(III)/Kg(II) ratio (1.32) was not as close to the predicted value of 2 as was Hoffman's ratio. For PEEK, the Thomas-Staveley constant (β) should be closer to 0.25 or 0.3 instead of 0.1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1335-1348, 1998
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  • 10
    Electronic Resource
    Electronic Resource
    Structure and morphology of nylon 2 4 lamellar crystals: Comparison with polypeptides and relationship with other nylons (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2401-2412 
    Details
    ISSN: 0887-6266
    Keywords: nylon 2 4 ; chain folding ; lamellar crystals ; structure and morphology ; crystallization ; electron microscopy ; Brill transformation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chain-folded lamellar crystals of nylon 2 4 have been prepared from dilute solution by addition of poor solvent. Two crystal structures are observed at room temperature: a monoclinic form I, precipitated at elevated temperature, and a less-defined, orthorhombic form II, precipitated at room temperature. The unit cell parameters for both forms are similar to those reported for its isomer, nylon 3. Nylon 2 4 form II is a liquid-crystal-like or disordered phase, consisting of hydrogen-bonded sheets in poor register in the hydrogen bond direction. Form I crystals have two characteristic interchain spacings of 0.41 nm and 0.39 nm at room temperature and on heating, exhibit a structural transformation and a Brill temperature (250°C) characteristic of many other even-even nylons. Nylon 2 4 is a member of the nylon 2 Y and nylon 2N 2(N+1) families, and the form I crystals show behavior commensurate with both. We propose they contain a proportion of intersheet hydrogen bonds at room temperature, similar to that for the nylon 2 Y family, and the short dimethylene alkane segments mean that the structure consists of hydrogen-bonded a-sheets, with an amide unit in each fold, similar to that of nylon 4 6. The fold geometry and sheet structure is compared with chain-folded apβ-sheet polypeptides and nylon 3. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2401-2412, 1998
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  • 11
    Electronic Resource
    Electronic Resource
    Observations of crystallization and melting in poly(ethylene oxide)/poly(methyl methacrylate) blends by hot-stage atomic-force microscopy (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2643-2651 
    Details
    ISSN: 0887-6266
    Keywords: poly(ethylene oxide) ; poly(methyl methacrylate) ; blends ; atomic-force microscopy ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The binary blend of poly(ethylene oxide)/atactic poly(methyl methacrylate) is examined using hot-stage atomic-force microscopy (AFM) in conjunction with differential scanning calorimetry and optical microscopy. It was found possible to follow in real time the melting process, which reveals itself to be nonuniform. This effect is ascribed to the presence of lamellae having different thicknesses. The crystallization process of poly(ethylene oxide) from the miscible melt is also followed in real time by AFM, affording detailed images of the impingement of adjacent spherulites and direct observation of lamellar growth and subsequent polymer solidification in the interlamellar space.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2643-2651, 1998
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  • 12
    Electronic Resource
    Electronic Resource
    Rheology of rodrun liquid-crystalline polymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 253-263 
    Details
    ISSN: 0887-6266
    Keywords: thermotropics ; dynamic viscoelasticity ; relaxation peaks ; gelation ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The rheological characterization of two commercial thermotropic liquid crystalline polymers based on poly(ethylene terephthalate) (PET) and para-hydroxybenzoic acid (PHB) is carried out. The thermal transitions determined by DMTA are explained by the random character of these copolyesters, in comparison with non-random copolyesters synthesized by Jackson and Kuhfuss. The evolution of the dynamic viscoelastic functions with time in the nematic state is concave in shape for the 20%PET/80%PHB copolymer, a result that leads us to treat this system as a suspension of solid spheres (unmolten crystals) where the volume fraction of crystals increases with time according to an Avrami equation. The response of 40%PET/60%PHB copolymer is similar to a chemical or physical gelation and the hypothesis that the polydomain structure gives rise to a network is considered. Continuous flow, time-independent viscosity results reveal the existence of a three-region flow curve for 40%PET/60%PHB copolymer, but a Newtonian zone followed by a shear thinning region for 20%PET/80%PHB sample. At high temperatures the isotropization of the samples leads to a very strong decrease of the activation energy of flow, which becomes zero for 40%PET/60%PHB. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 253-263, 1998
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  • 13
    Electronic Resource
    Electronic Resource
    Effect of crystallization temperature on the phase transitions of P(VDF/TrFE) copolymers (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 403-414 
    Details
    ISSN: 0887-6266
    Keywords: P(VDF/TrFE) copolymer ; phase transition ; ferroelectric ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A systematic study was carried out on the effect of the crystallization temperature (Tcr), on the phase transitions presented by P(VDF/TrFE) copolymers cast from dimethylformamide (DMF) solution with molar ratios 60/40, 70/30, and 80/20. The results obtained by differential scanning calorimetry (DSC) showed that two-phase transitions are observed only when the copolymer crystallizes above a certain temperature To, and that the temperatures at which these transitions occur are reduced slightly with Tcr increase. It also was observed that when Tcr increases, the intensity of the endotherm corresponding to the lowest temperature transition is increased, whereas the one corresponding to the highest temperature transition is reduced. In order to explain these phenomena, the existence of two ferroelectric and two paraelectric phases is suggested. The conformational differences between like phases occur due to the distinct origin of each one: the best organized phase crystallizes directly from solution, whereas the least organized is the result of a solid phase transition. Wide angle x-ray diffusion (WAXD) diffractograms corroborate this hypothesis. Phase diagrams for samples crystallized below and above To have been proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 403-414, 1998
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  • 14
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    Blends of polycarbonate and acrylic polymers: Crystallization of polycarbonate (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2197-2210 
    Details
    ISSN: 0887-6266
    Keywords: polycarbonate ; PMMA ; polyglutarimide ; crystallization ; segregation ; AFM ; SAXS ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The microstructure of amorphous polymer blends has been extensively studied in the past, but now there is a growing interest for polymer blends where one or more of the components can crystallize. In this study we investigate such blends, namely miscible polycarbonate (PC)/acrylic blends. Using small angle X-ray scattering (SAXS) measurements, combined with atomic force microscopy (AFM), electron microscopy (SEM), and optical microscopy, we demonstrate that the amorphous acrylic component mostly segregates inside the spherulites between the lamellar bundles (interfibrillar segregation). Varying the PC molecular weight or the mobility of the amorphous component (by changing its molecular weight and Tg) does not change the mode of segregation. So far qualitative predictions of the mode of segregation in semicrystalline polymer blends have been proposed using the δ parameter (the ratio between the diffusion coefficient D of the amorphous component in the blend and the linear crystallization rate G), introduced by Keith and Padden. Our results suggest that other parameters have to be considered to fully understand the segregation process. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2197-2210, 1998
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  • 15
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    AFM study of morphological development during the melt-crystallization of poly(ethylene oxide) (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2311-2325 
    Details
    ISSN: 0887-6266
    Keywords: poly(ethylene oxide) ; crystallization ; AFM ; spherulites ; crystal growth ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The atomic force microscope (AFM) has been used to investigate morphological development during the crystallization of poly(ethylene oxide) (PEO) from the melt. PEOs with molecular weights of 1 × 105 and 7 × 106 were used. Height and amplitude images were recorded, using the tapping mode. For both polymers, the mode of spherulite development varied with the velocity of the growth front. For slow growth velocities, the growth of the crystallites was linear, with growth initially occurring by single lamellae, later developing into growth arms by screw dislocation spawning of crystallites. At intermediate growth velocities, stacks of lamellae develop rapidly. The splaying apart of adjacent crystals and growth arms is abundant. The operation of growth spirals was observed directly in this growth velocity range. The crystals formed by the giant screw dislocations diverge immediately from the original growth direction, providing a source of interlamellar splaying. At low and intermediate velocities, the front propagates by the advance of primary growth arms, with the regions between the arms filled in by arms growing behind the primary front. At the highest velocity observed here, the formation of lamellar bundles and immediate splaying results in recognizable spherulites developing at the earliest stages of crystallization. The change from linear growth to splaying and nonlinear growth are qualitatively explained in terms of driving force, elastic resistance and the presence of compositional and/or elastic fields in the melt. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2311-2325, 1998
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  • 16
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    Analysis of crystallization kinetics of poly(ether ether ketone) by a nonisothermal method (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2393-2399 
    Details
    ISSN: 0887-6266
    Keywords: PEEK ; nonisothermal ; growth rate ; crystallization ; kinetics ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: During cooling at a rate of 10°C/min from the melt state of PEEK we have followed the growth of spherulites using an optical microscope equipped with a camera. The isothermal growth rates of crystallization in the temperature range of 266-308°C could be estimated by means of a differential equation. These continuous growth rate data were used further for kinetic analysis, which indicated that PEEK exhibited an unmistakable regime II → III transition at 296°C. The results compared favorably with those obtained by the traditional isothermal method, which is time consuming. Due to chain folding, the Thomas-Staveley constant should be closer to 0.25 instead of 0.1 or 0.3. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2393-2399, 1998
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  • 17
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    Crystallization-induced composition inhomogeneities in PVDF/PMMA blends (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2923-2930 
    Details
    ISSN: 0887-6266
    Keywords: polymer blends ; crystallization ; diffusion ; composition inhomogeneities ; internal spherulite structure ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Composition profiles develop around growing PVDF spherulites in a blend with PMMA. These profiles assume stationary courses after a certain crystallization time provided that the overall degree of crystallinity is not too high. The composition-dependent growth rate and the diffusion-controlled remove of the surplus PMMA from the spherulite surface are then in a stationary equilibrium. The internal structure of the spherulites will then be homogeneous, too. Upon isothermal crystallization of a PVDF/PMMA = 60/40 (wt %) blend at 160°C for at least 4 h, the spherulites internal degree of crystallinity xc as related to the PVDF fraction obeys the inequality 55 wt % ≤ xc ≤ 84 wt %. The overall PMMA content within the spherulites as averaged over its whole inside has been determined by IR microscopy. It amounts to about 15 wt %. In contrast, the PMMA content of the amorphous phase within the spherulites (averaged again over its whole inside) ranges between 28 and 52 wt %. This composition jumps at the spherulite surface to 52 wt %. From the slope of the composition profiles outside the spherulites that have a width of more than 50 μm, the effective chain diffusion coefficient in blends as averaged over both components can be calculated to amount to (250 ± 100) μm2h-1. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 2923-2930, 1998
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    Crystallization from the melt at high supercooling in finely dispersed polymer blends: DSC and rheological analysis (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 2573-2585 
    Details
    ISSN: 0887-6266
    Keywords: polyethylene ; poly(butylene terephthalate) ; blend ; rheology ; Palierne's model ; morphology ; differential scanning calorimetry ; crystallization ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystallization at high supercooling of polybutylene terephthalate (PBT) droplets dispersed in a molten polyethylene (PE) matrix was investigated through rheological and DSC experiments. The Palierne's emulsion model was used as a theoretical framework for studying the viscoelastic behavior of the blends in different ranges of temperature: on the one hand, when the two polymers are molten (T 〉 225°C) and on the other hand, when PBT droplets are at high supercooling in the molten PE matrix (130°C 〈 T 〈 205°C). From rheological experimental evidences it was shown that molten and solidified droplets coexist at high supercooling. The Palierne's model was then successfully adapted to take into account the three phases (molten PE, molten PBT droplets, and solidified PBT droplets). The evolution of the behavior with the temperature is consistent with the growing amount of crystallized droplets. Moreover, a calculation taking into account the droplets size distribution and the number of nuclei is introduced to explain the crystallization behavior of three different blend ratios.© 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2573-2585, 1998
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    The phase morphology and crystal growth habits of DNA fractions. Optical microscopy and light scattering (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1843-1854 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; DNA ; fractionation ; gel-electrophoresis ; morphology ; phase transition ; SALLS ; sonication ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polydisperse DNA of reasonable molecular weights was prepared from a mammalian source via sonication and fractionation. A method for characterizing the molecular weight using gel electrophoresis is described. Quiescent crystallization was studied in thin films of one of the fractions induced by rapidly changing the hydration state isothermally. We report the occurrence of the semicrystalline nature of DNA. The crystal growth occurring via aggregates is best described as sheaves and spherulites from DNA gels in the relative humidity range (RH) corresponding to A-DNA. These habits exhibit primary nucleation and secondary growth, which closely resemble those of melt-crystallized, synthetic macromolecules and, in a follow-up report, will be shown to be lamellar in nature. Small, needle-like crystals are observed for B-DNA hydration levels, and are unstable at lower hydration levels. A transformation from needle to lamellar crystals can occur, even when the primary nucleation of lamellar forms is otherwise absent at that hydration level, through a cylindrical phase exhibiting selective reflection of colored bands. The hydration level plays, in part, the role of the supercooling in this system and the long-known hysteresis in the formation and dissolution of the A-DNA (crystals) can now be viewed in light of those factors known to operate in semicrystalline systems. A morphological phase diagram is developed and is in accord with the known physical evidence. Because this preparation and these morphological observations are without precedence, substantial detail into methodology is included for this first article in the series. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1843-1854, 1997
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    The effect of highly specific lattice hydrogen bonding on morphologies of solution-grown crystals (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1175-1183 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; morphology ; chain folding ; lamella ; hydrogen bonding ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphologies of solution-grown crystals in systems containing strong and specific intralattice hydrogen bonding (nylons) are compared with systems displaying only van der Waals intracrystal attractions. The latter are shown to produce crystals that clearly mirror the underlying crystallographic symmetry; in the former systems the morphologies are much more complex and disorganized. This difference is discussed in terms of intralattice forces affecting growth rates and chain rearrangement during crystallization. Arguments deriving from differences in lamellar thickening behavior are also used to demonstrate this point. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1175-1183, 1997
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    Structural analysis of minimized models for syndiotactic polypropylene (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2523-2533 
    Details
    ISSN: 0887-6266
    Keywords: chirality ; morphology ; structure ; crystallization ; defects ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In previous work we have shown that the stable form of syndiotactic polypropylene (sPP) adopts a fully antichiral packing in its crystalline lattice. At the same time, we had also discovered a number of prohibited reflections from crystallographic planes with a c-axis component, indicating distortions or defects along the molecular-chain direction and possible departures from the ideal Ibca unit-cell structure. Three studies that appeared in 1996 have proposed a number of possible minimized structures to explore the energetics of departure from such an ideal Ibca symmetry and to account for the prohibited reflections. Two of the studies were based upon energy minimization of the unit cell using empirical or spectroscopically derived force fields. The third model was based upon Rietveld refinement of the bulk X-ray diffractogram combined with ad hoc choices of space groups selected to reproduce the prohibited reflections, and results in a structure with minimal departures from Ibca. In the present article we examine the structural implications of all these models on various reciprocal-lattice sections of sPP by comparing calculated electron-diffraction patterns for appropriate zones with those we obtained experimentally from single crystals. We find that none of the proposed models fully accounts for the experimental data. One of the energy-minimized models (involving translation along the molecular axis) and the Rietveld-refined structure reproduce some of the observed reflections but are not in agreement with observed intensities and introduce additional unobserved reflections or other artifacts. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2523-2533, 1997
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    Autohesion of crosslinked polyethylene (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 615-622 
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    ISSN: 0887-6266
    Keywords: adhesion ; crystallization ; peeling ; plastic yielding ; polyethylene ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin strips of crosslinked linear high-density polyethylene were melted and then crystallized in contact by cooling to room temperature. The work required to peel the strips apart by pulling one strip away from the other at 90° was found to be remarkably high, 5 to 30 kJ/m2, and in some cases the strips could not be separated in this way. However, adhesion measured in T-peeling was much lower, about one-tenth as large. Adhesion was also fairly small, 200 to 600 J/m2, using other test methods designed to minimize bending strains. Thus, most of the work of separation is normally expended in bending, probably in plastic yielding of the outer layers of bent strips. However, even when bending energy losses were minimized, the residual adhesion was much greater than expected for Van der Waals bonding (about 0.05 J/m2). Apparently, cocrystallization of molecular strands lying on either side of the interface greatly enhances the intrinsically low level of autohesion of amorphous polyethylene, probably by local yielding processes around the line of separation. Some effects of test temperature were also examined in T-peeling. Adhesion passed through a pronounced maximum at temperatures of 75-100°C before reducing to very low values in the melted state. This maximum was absent in tests with reduced bending. It is, therefore, attributed to extra work expended in plastic bending over a narrow range of temperature, probably due to a lower yield stress at these temperatures and not to an increase in the actual adhesion. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 615-622, 1997
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    Structure and properties for binary blends of isotactic-polypropylene with ethylene-α-olefin copolymer. 1. Crystallization and morphology (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 953-961 
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    ISSN: 0887-6266
    Keywords: ethylene-1-hexene copolymer ; polypropylene ; polymer blend ; miscibility ; crystallization ; morphology ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphology and isothermal growth rates of spherulites for the binary blends consisting of an isotactic polypropylene (i-PP) and an ethylene-1-hexene rubber (EHR) were examined as a function of the crystallization temperature ranging from 388 K to 418 K. In this study, two types of EHR's were employed: “ethylene rich” EHR and “1-hexene rich” EHR. The blends of i-PP with the EHR of 51 mol % 1-hexene are miscible in the molten state, whereas the blends with the EHR of 33 mol % 1-hexene are immiscible in the molten state. It is found that the isothermal spherulite growth rate of the miscible i-PP/EHR blends decreases with increasing the EHR fraction, whereas the spherulite growth rate of the immiscible i-PP/EHR blends is independent of the blend composition and is the same as that of the i-PP. Optical microscope observation of the miscible blends crystallized isothermally shows that there are no rubber domains either in the intraspherulitic or in the interspherulitic contact regions. On the other hand, the immiscible i-PP/EHR blends show a phase-separated morphology. Furthermore, the number of tangential lamellae of the miscible i-PP/EHR blends is found to be increased by blending of the EHR, leading to the spherulite with negative birefringence. The sign of birefringence of spherulites is unaffected by the regime transition as well as by the fold surface free energy. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 953-961, 1997
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    Crystallization and melting of poly(oxyethylene) analyzed by temperature-modulated calorimetry (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1877-1886 
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    ISSN: 0887-6266
    Keywords: temperature-modulated calorimetry ; TMC ; temperature-modulated differential scanning calorimetry ; TMDSC ; melting ; crystallization ; molecular nucleation ; poly(oxyethylene) ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Temperature-modulated calorimetry, TMC, is used to evaluate the temperature region of metastability between crystallization and melting. While crystals like indium can be made to melt practically reversibly during a TMC cycle of low amplitude so that sufficient crystal nuclei remain unmelted, linear macromolecules cannot, because of their need to undergo molecular nucleation. Modulation amplitudes varying from ±0.2 to ±3.0 K are used to assess the temperature gap between the slow crystallization region and the melting of metastable crystals of poly(oxyethylene) (PEO) of molar mass 1500 Da. This low molar mass PEO serves as a model compound with a metastable gap of melting/crystallization that can be bridged by TMC with a large modulation amplitude. © 1997 John Wiley & Sons, Inc.This article is a US Government work and, as such, is in the public domain in the United States of America. J Polym Sci B: Polym Phys 35: 1877-1886, 1997
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    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
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    Modeling of the crystallization of isotactic polypropylene chains (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2757-2764 
    Details
    ISSN: 0887-6266
    Keywords: Monte Carlo simulations ; polypropylene ; isotacticity ; sequence distributions ; crystallization ; degrees of crystallinity ; melting points ; mechanical properties ; moduli ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanical properties of polypropylene depend critically on the crystallizability of the chains, which depends in turn on their stereochemical structures. These dependences were investigated using Monte Carlo methods to generate chains having various stereochemical sequences and then scrutinizing parallel arrays of these chains to look for matches in isotactic stereochemistry that could lead to the formation of crystallites. The fraction of such units in matches, for example, gives a direct measure of the degree of crystallinity expected for the specified degree of isotacticity. Other quantities of interest obtainable in this way were the natures of the sequence distributions themselves, melting points, free energies of fusion, interfacial free energies, and moduli (calculated on the basis of the crystallites acting as crosslinks within an elastomeric network structure). © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2757-2764, 1997
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    Fiber period of chondroitin sulfate and its mechanical history (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2771-2773 
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    ISSN: 0887-6266
    Keywords: chondroitin sulfate ; fiber period ; x-ray diffraction ; annealing ; crystallization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Without elongational treatments, the fiber period of chondroitin-4-sulfate (0.87 nm) is shorter than in the elongated case (0.96 nm). The fiber period may change corresponding to its mechanical history. © 1996 John Wiley & Sons, Inc.
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    A monotropic liquid crystal polyester with a biphasic nematic-smectic phase (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2077-2084 
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    ISSN: 0887-6266
    Keywords: liquid crystals ; polyesters ; nematic-smectic biphase ; monotropic ; crystallization ; optical textures ; DSC ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polyesters made from the condensation of isophthalic acid (IA) or terephthalic acid (TA) with the mesogenic diol 4,4′-bis (6-hydroxy hexoxy)biphenyl (BHHBP) are both reported to show a smectic mesophase. However, in our previous work, we found evidence for a mesophase in the polyester containing BHHBP and IA, but not in the one with BHHBP and TA. For the BHHBP-IA polyester, we thought the phase sequence on cooling was I → SA → K, while on heating the situation was unresolved; there was some indication that on heating, a K → I transition occurs without any intervening mesophase. In other words, it was suspected that the mesophase in the IA polyester was monotropic. In this work, we have now obtained firm evidence that the mesophase behavior of the BHHBP-IA polyester is indeed monotropic. Further, an additional complexity has been found: on cooling, there is in fact a nematic phase, besides a smectic A, and a crystal phase. However, the mesophase appears to be complex. As the nematic and smectic textures occurred simultaneously, it seems that the mesophase is a nematic-smectic biphase. © 1996 John Wiley & Sons, Inc.
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    An atomic force microscope (AFM) and tapping mode AFM study of the solvent-induced crystallization of polycarbonate thin films (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 173-180 
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    ISSN: 0887-6266
    Keywords: AFM ; tapping mode AFM ; thin films ; polycarbonate ; solvent ; crystallization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin films of bisphenol-A polycarbonate (PC) were progressively crystallized in a controllable manner under the action of an appropriate plasticizing agent. No conducting layer was applied to the polymer surface, so that imaging with the atomic force microscope (AFM) left the sample exposed for additional plasticizer treatment. The PC sample was observed many times throughout the crystallization process using the AFM in both the contact and tapping modes. Data regarding the growth process for spherulites in addition to high-resolution morphology studies were achieved. © 1996 John Wiley & Sons, Inc.
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    The competition between crystallization and demixing in polymer blends. V. Numerical modeling and quantitative evaluation of crystallization-induced composition inhomogeneitiesParts I through IV cf. refs. 1-4 (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 893-900 
    Details
    ISSN: 0887-6266
    Keywords: polymer blends ; crystallization ; diffusion ; composition inhomogeneities ; computer simulation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is well known that crystallization of one component in a polymer blend causes composition profiles around the growing spherulites. Amplitude and width of these profiles, respectively, depend on the ratio between the rates of diffusion and of spherulite growth. They can be determined by suitable experimental means. In the present article, the profiles are modeled, starting from Frank's solution of the diffusion equation in spherical coordinates under the boundary condition of moving walls that simultaneously are sources of the diffusing material. Modeled and experimentally determined profiles in PVDF/PEA and PCL/PS blends agree well. The analysis yields estimates for the diffusion coefficient D in polymeric melts as D ≅ (50··· 500) μm2/h. Finally, the interference of the composition profiles around several adjacent spherulites can be demonstrated. © 1996 John Wiley & Sons, Inc.
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    Effect of thermal history on the melting behavior and the crystal-crystal transitions of tetrafluoroethylene-perfluoroalkylvinylether copolymers (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1751-1759 
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    ISSN: 0887-6266
    Keywords: tetrafluoroethylene-perfluoroalkylvinylether copolymers ; melting ; crystallization ; annealing ; crystal-crystal transitions ; differential scanning calorimetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By differential scanning calorimetry (DSC), the effect of thermal treatments on the melting of tetrafluoroethylene-perfluoroalkylvinylether copolymers (PFA) with different contents of perfluoromethylvinylether as a comonomer has been investigated. Two melting peaks can be identified for all copolymers, whose presence, value, and extent depend upon the thermal treatments. The higher temperature one, scarcely influenced by the crystallization conditions (i.e., cooling rate and annealing), can be attributed to more perfect crystals present in the original samples. The lower temperature one is produced only by annealing (annealing peak) and can be interpreted as resulting from much poorer crystals grown among the larger ones. For the copolymer with the lowest content of comonomer, the effect of thermal treatments on the low-temperature (crystal-crystal) transitions has also been studied. The rejection of the counits from the crystals, at least in equilibrium conditions, is confirmed. © 1996 John Wiley & Sons, Inc.
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    A morphological study of membranes obtained from the systems polylactide-dioxane-methanol, polylactide-dioxane-water and polylactide-N-methyl pyrrolidone-water (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2569-2578 
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    ISSN: 0887-6266
    Keywords: polylactide ; membrane formation ; morphology ; crystallization ; liquid-liquid demixing ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The influence of liquid-liquid demixing, solid-liquid demixing, and vitrification on the membrane morphologies obtained from several polylactide-solvent-nonsolvent systems has been investigated. The polymers investigated were the semicrystalline poly-L-lactide (PLLA) and the amorphous poly-DL-lactide (PDLLA). The solvent-nonsolvent systems used were dioxane-water, N-methyl pyrrolidone-water and dioxane-methanol. For each of these systems it was attempted to relate the membrane morphology to the ternary phase diagram at 25°C. It was demonstrated that for the amorphous poly-DL-lactide the intersection of a glass transition and a liquid-liquid miscibility gap in the phase diagram was a prerequisite for the formation of stable membrane structures. For the semicrystalline PLLA a wide variety of morphologies could be obtained ranging from cellular to spherulitical structures. For membrane-forming combinations that show delayed demixing, trends expected on the basis of phase diagrams were in reasonable agreement with the observed membrane morphologies. Only for the rapidly precipitating system PLLA-N-methyl pyrrolidone-water were structures due to liquid-liquid demixing obtained when structures due to solid-liquid demixing were expected. Probably, rapid precipitation conditions promote solid-liquid demixing over liquid-liquid demixing, because the activation energy necessary for liquid-liquid demixing is lower than that for crystallization. © 1996 John Wiley & Sons, Inc.
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    Crystallization, thermal behavior, and compatibility of poly(ethylene oxide)/poly(propylene oxide) blends (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2715-2721 
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    ISSN: 0887-6266
    Keywords: crystallization ; PEO ; PPO ; blends ; compatibility ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isothermal and nonisothermal crystallization kinetics of different poly(ethylene oxide)/poly(propylene oxide) blends were investigated by means of differential scanning calorimetry (DSC). Glass transition temperature of quenched samples have also been reported. Phase morphologies and poly(ethylene oxide) spherulite growth rates were analyzed by polarizing light transmission microscopy. Results show morphological changes along with regime transitions of poly(ethylene oxide) crystal growth. Kinetic analyses of the data suggest that, although the blend behaves as a noncompatible, phase-separated system, there exists a certain degree of interaction between polymer chains. © 1996 John Wiley & Sons, Inc.
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    Rules of supermolecular structure formation in sheared isotactic polypropylene melts (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 657-670 
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    ISSN: 0887-6266
    Keywords: α-polypropylene ; β-polypropylene ; crystallization ; cylindrite ; isotactic polypropylene ; melting ; nucleation ; quiescent melt ; sheared melt ; supermolecular structure ; thermo-optical study ; transcrystallization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Shear-induced crystallization of isotactic polypropylene (iPP) homo-, block, and random copolymers was studied and compared to that in quiescent melt. It was evidenced by means of the thermo-optical technique that melt-shearing, caused by fiber pulling, is associated with the development of α-row-nuclei. The surface of the in situ formed α-row-nuclei may induce the growth of the β-modification of iPP resulting in a cylindrite of polymorphous composition. The polymorphous composition is controlled by the temperature-dependent relative growth rate of the α- and β-iPP for which a model explanation was given. The β-nucleation ability of the α-row-nuclei is lost by melt-shearing at high temperature or remelting. This was attributed to a coverage of the β-nuclei by the α-phase. The structural memory of the supermolecular structures was studied in repeated melting and crystallization cycles and discussed. It was found that the quality of the fiber did not influence the mechanisms concluded. The shear-induced crystallization of propylene block copolymers was highly analogous to the homopolymers. In case of the random copolymers, however, crystallization in sheared melt resulted in an α-cylindritic structure, because for propylene random copolymers the growth rate of the α-modification is always higher than that of the β. It was also demonstrated that the mechanism of shear-induced crystallization was unaffected when the crystallizing PP melt contained selective β-nucleants. © 1996 John Wiley & Sons, Inc.
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    Anomalous two-stage spherulite growth in poly(aryl ether ketones) during isothermal crystallization (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 3095-3105 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; spherulite ; anomalous growth ; poly(aryl ether ketones) ; optical microscopy ; SALS ; SAXS ; lamellar structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Anomalous two-stage spherulite growth has been observed in poly(aryl ether ketones) during isothermal crystallization. The first stage consists of a conventional growth with Maltesecross pattern at a lower growth rate. The morphology shows a smooth interface, dense structure and negative birefringence. The second stage grows in the form of “aggregate” at a higher rate. The morphology shows an open dendrite structure without preferred optical orientation. The second morphology is also termed the “overgrowth.” The occurrence of overgrowth is favored only near the maximum growth rate region and diminishes in the slow growth region. The transition of the two-stage growth is attributed to the change of growth direction of the constituent lamellae. We have confirmed this by microbeam small-angle light-scattering measurements. The lamellar structures in both growth stages were followed by time-resolved small-angle synchrotron x-ray scattering. It was found that the lamellar structures of the crystals formed at both stages are the same. A possible explanation for the two-stage growth is the interface breakdown caused by large perturbations of local composition and/or stress fields. © 1996 John Wiley & Sons, Inc.
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    Morphology development during solid-state annealing of poly(ether-ester) multiblock copolymers (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 737-749 
    Details
    ISSN: 0887-6266
    Keywords: poly(ether-ester) ; multiblock ; poly(tetramethylene isophthalate) ; crystallization ; melting ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Morphology development during isothermal annealing of poly(ether-ester) multiblock copolymers with hard segments containing poly(tetramethylene isophthalate) is examined by differential scanning calorimetry (DSC) and small-angle x-ray scattering (SAXS). Reorganization in the solid-state occurs by melting and recrystallization. At temperatures close to the melting point, glass transition measurements after quenching from the annealing temperature suggest microphase mixing follows melting. The temperature of maximum recrystallization rate is elevated relative to that of isothermal crystallization. SAXS experiments suggest that a memory of the initial morphology is retained during annealing. Aspects of the DSC scans related to crystallization on cooling and rescanning also suggest that the morphology at the annealing temperature plays a governing role in the determination of the degree of order possible on cooling. The crystalline regions stable at the annealing temperature are envisioned to function in a dual role, acting as nucleation centers for recrystallization and as a form of “constraint” to ordering on cooling. © 1996 John Wiley & Sons, Inc.
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    A continuum model for the dynamics of flow-induced crystallization (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2393-2407 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; orientation ; flow ; kinetics ; stress ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A model for flow-induced crystallization is developed which is based on ideas from the theory of strain-induced crystallization, coupled with an irreversible thermodynamic formalism based on the continuum Hamiltonian Poisson Brackets. The latter allows accounting for the changing energetics during simultaneous flow deformation and extended-chain crystallization. Input parameters to the model include the molecular relaxation time, a crystallization parameter, and the molecular weight. Calculations of the crystallization rate, chain elongation, stress, and birefringence are presented for a variety of flow kinematics and flow histories, including transient processes following cessation of flow. Induction times based on a reasonable choice for the induction crystallinity follow experimentally observed trends reported in the literature. © 1996 John Wiley & Sons, Inc.
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    Phase transitions in two polyesters containing a smectic diol (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1957-1967 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystals ; polyesters ; smectic mesophase ; crystallization ; optical textures ; DSC ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work reports the phase behavior of the polyesters made from the condensation of isophthalic acid (IA) and terephthalic acid (TA) with the mesogenic diol 4,4′-bis (6-hydroxy hexoxy) biphenyl (BHHBP). The latter monomer forms a smectic mesophase in the interval 98-179°C. Fischer et al., who investigated the room temperature x-ray patterns of the oriented polyesters of BHHBP and IA, as well as BHHBP and TA, claimed that both polymers also showed smectic mesophases. However, they showed no other evidence to support their interpretation. In the present work, examination of these polyesters under the optical microscope revealed focal conic textures for the IA polyester, but spherulitic textures for the TA polyester. DSC studies revealed thermograms with two peaks in the cooling scan for the IA polyester, at different cooling rates, which supported the view that there were two phase transitions. The heating scans of the TA polyester showed multiple peaks that depended on heating rate whereas on cooling, only a single exothermic peak was observed at all cooling rates. Thus, the current results definitely support the case for a smectic A mesophase in the IA polyester but, contrary to Fischer et al.'s opinion, do not suggest any mesophase formation in the TA polyester. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/polb.1995.090331311
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    Structure and molecular conformation of tussah silk fibroin films: Effect of methanol (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1995-2001 
    Details
    ISSN: 0887-6266
    Keywords: tussah silk fibroin ; methanol treatment ; molecular conformation ; crystallization ; Raman spectroscopy analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Structural changes of tussah (Antheraea pernyi) silk fibroin films treated with different water-methanol solutions at 20°C were studied as a function of methanol concentration and immersion time. X-ray diffraction measurements showed that the α-helix structure, typical of untreated tussah films, did not change for short immersion times (2 min), regardless of methanol concentration. However, crystallization to β-sheet structure was observed following immersion of tussah films for 30 min in methanol solutions ranging from 20 to 60% (v/v). IR spectra of tussah films untreated and methanol treated for 2 min exhibited strong absorption bands at 1265, 892, and 622 cm-1, typical of the α-helix conformation. The intensity of the bands assigned to the β-sheet conformation (1245, 965, and 698 cm-1) increased for the sample treated with 40% methanol for 30 min. Raman spectra of tussah films with α-helix molecular conformation exhibited strong bands at 1657 (amide I), 1263 (amide III), 1106, 908, 530, and 376 cm-1. Following α → β conformational transition, amide I and III bands shifted to 1668, and to 1241, 1230 cm-1, respectively. The band at 1106 cm-1 disappeared and new bands appeared at 1095 and 1073 cm-1, whereas the intensity of the bands at 530 and 376 cm-1 decreased significantly. ©1995 John Wiley & Sons, Inc.
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    Solvent-induced crystallization of nylon-6I (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 619-627 
    Details
    ISSN: 0887-6266
    Keywords: nylon-6I ; crystallization ; x-ray diffraction ; differential scanning calorimetry ; infrared spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The ability of various hydrogen bond-forming solvents to induce crystallinity in nylon-6I was studied using DSC, FTIR spectroscopy, and x-ray diffraction. Comparison was made with predictions using the solubility parameter, which is related to possibilities of interaction formation. General predicted tendencies agreed with experimental results, in agreement with proposed influence of solvent-polymer interactions in the solvent-induced crystallization process. FTIR investigation of polymers treated with methanol and methanol-d shows that polymer segments forming hydrogen bonds with solvent molecules crystallize preferentially. It is therefore concluded that hydrogen bond exchanges with the solvent favor chain rearrangements leading to crystallization. © 1995 John Wiley & Sons, Inc.
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    Crystallization kinetics for semicrystalline random copolymers of vinylidene chloride (VDC) with methyl acrylate (MA), and the effects on the internal morphology of the resin particles formed during synthesis (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 2019-2032 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; random copolymers ; heterogeneous polymerization ; resin beads ; particle morphology ; noncrystallizable units ; SEM ; specific surface area ; vinylidene chloride ; methyl acrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isothermal crystallization kinetics for random copolymers of vinylidene chloride (VDC) with methyl acrylate (MA) is reported. Syntheses of many semicrystalline polymers follow heterogeneous reaction paths in which the macromolecule chains phase separate from the reaction mixtures. The internal particle morphology (the internal structure of the resin bead) from this type of reaction is granular and porous, as a result of the demixing processes accompanying polymer formation. Demixing in these polymers involves either liquid-liquid (L-L) phase separation followed by liquid-solid (L-S) transformation (crystallization) or L-S transformation alone. Crystallization (L-S transformation) must be an indispensable part of the process if a porous granular structure is to be expected. This is because L-S transformation is the most probable means by which the demixed structure can be stabilized against complete coalescence or agglomeration, which would lead to totally fused bead internal structure. This is particularly true if the glass transition temperature (Tg) is lower than the polymerization temperatures, as is the case with the VDC-MA copolymers. Copolymers that crystallize the fastest will have the finest (most porous) resin bead morphology. The result of this work is consistent with expectation. The homopolymer (PVDC) that crystallizes the fastest has the finest resin bead internal morphology. The copolymers show slower crystallization rates with increasing noncrystallizable MA content. Correspondingly, resin morphology measured by specific surface area decreased with increasing amounts of the noncrystallizable (MA) comonomer unit in the copolymer. This is clearly seen in SEM photographs of the internal bead structures of these copolymers. ©1995 John Wiley & Sons, Inc.
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    On the triple melting behaviour of poly(ethylene succinate) (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 37 (1995), S. 249-254 
    Details
    ISSN: 0959-8103
    Keywords: poly(ethylene succinate) ; crystallization ; morphology ; electron microscopy ; thermal analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The morphology of melt-crystallized poly(ethylene succinate) (PES) was investigated by optical microscopy and scanning electron microscopy, and the melting behaviour of PES was studied by differential scanning calorimetry (DSC). At low crystallization temperature imperfect crystals were formed which could melt and recrystallize during the DSC scan. Triple melting peaks were observed, and the melting behaviour was strongly dependent on crystallization time and scan rate. It was observed that crystallization at high temperature perfected the crystals (dominant and subsidiary lamellae in the spherulitic structure). Increasing the scan rate reduced the chance for reorganization. However, at high crystallization temperature two melting peaks were observed. The material formed was much more perfect, so that the melting process was not dominated by recrystallization. Accordingly, the cause of dual melting is the existence of two kinds of crystal perfection.
    Additional Material: 10 Ill.
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    Morphology and melting behaviour of poly(ethylene terephthalate) crystallized from the glassy state (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 367-373 
    Details
    ISSN: 0959-8103
    Keywords: poly(ethylene terephthalate) ; annealing ; thermal behaviour ; morphology ; crystallization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The influence of annealing conditions on the morphology and melting behaviour of poly(ethylene terephthalate) (PET) was studied. PET annealed under isothermal conditions often shows double melting endotherms depending on the annealing temperature (Ta) and the heating rate of the calorimeter. It was found that the morphological structure and the lower melting peak depend strongly on the annealing temperature, Ta. The increase of the lower melting peak temperature with Ta is due to an increase of the lamellar thickness within the spherulitic structure and to a higher crystallite perfection.
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    Morphology and melting behaviour of poly(vinylidene fluoride) crystallized from the melt (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 381-385 
    Details
    ISSN: 0959-8103
    Keywords: poly(vinylidene fluoride) ; crystallization ; thermal behaviour ; morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The influence of crystallization temperature on the melting behaviour and the morphology of poly(vinylidene fluoride) (PVF2) has been investigated. The DSC endotherms of PVF2 crystallized from the melt show at least two peaks. The peak areas depend on the thermal history of the samples and the heating scan rate. The area of the first peak was found to increase as the crystallization temperature or the scan rate increased. The double peak configuration was attributed to a melting-recrystallization process. Electron microscopy supports these results, for which only one type of lamella was found in the spherulitic structure.
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  • 45
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    Preparation of small poly(butylene terephthalate) spheres by crystallization from solution (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 573-577 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; nucleation ; spherulites ; liquid-liquid phase separation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallization of poly(butylene terephthalate) (PBT) from moderately dilute solutions of PBT in a diglycidyl ether of bisphenol-A epoxy has been investigated. PBT dissolves in this epoxy approximately 35°C below its usual melting temperature of 227°C to form a one-phase solution. Cooling this solution below 165°C leads to rapid crystallization of the PBT. The resulting mixture of liquid epoxy and crystalline PBT has a low viscosity and contains highly birefringent, individual PBT spherulites. The PBT spherulites have a narrow size distribution and a high surface-to-volume ratio. These particles are suggested to arise from a rapid crystallization that follows liquid-liquid phase separation. © 1994 John Wiley & Sons, Inc.
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    Isothermal phase behavior of Nylon-6, -66, and -610 polyamides in formic acid-water systems (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1183-1190 
    Details
    ISSN: 0887-6266
    Keywords: polyamide ; aliphatic ; crystallization ; binodal ; ternary ; phase diagram ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Concentration-dependent ternary interaction parameters are experimentally determined for the polyamide homopolymers, Nylon-6, -66, -610, and for the Nylon-66/610/6 terpolymer in formic acid-water systems. The binodal envelope, the tie lines, and the crystallization isotherms at 25°C are given for each of the ternary systems. © 1994 John Wiley & Sons, Inc.
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    Compatibilization of polypropylene/poly (ethylene oxide) blends and crystallization behavior of the blends (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1991-1998 
    Details
    ISSN: 0887-6266
    Keywords: polypropylene (PP) ; blend ; compatibilization ; crystallization ; fractionated crystallization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The compatibilization of incompatible polypropylene (PP)/poly(ethylene oxide) (PEO) blends was studied. The experimental results showed that the graft copolymer [(PP-MA)-g-PEO] of maleated PP(PP-MA) and mono-hydroxyl PEO (PEO-OH) was a good compatibilizer for the PP/PEO blends in which PP-MA also had some compatibilization. The crystallization of the blends was affected by the compatibility between PP and PEO. The interfacial behavior of the compatibilizers had an important effect on crystallization behavior of the PP/PEO blends. PEO showed fractionated crystallization in the PP/PEO blends. This behavior was studied from the view point of the theory of fractionated crystallization. © 1994 John Wiley & Sons, Inc.
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    Crystallization of poly(aryl ether ketone ketone) copolymers containing terephthalate/isophthalate moieties (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2585-2594 
    Details
    ISSN: 0887-6266
    Keywords: PEKK ; copolymer ; terephthalate/isophthalate ; structure ; crystallization ; melting ; x-ray diffraction ; thermal analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In a previous study, we have investigated the structure, crystallization, and morphology of poly(aryl ether ketone ketone), PEKK, copolymers prepared from diphenyl ether (DPE), terephthalic acid (T), and isophthalic acid (I) with T/I ratios from 100/0 to 50/50. These materials were considered as having -DPE-T-DPE-T- (TT) and/or -DPE-T-DPE-I- (TI) “phthalate diads.” In this work, we continue the study of this copolymer series with six different T/I ratios (40/60, 30/70, 20/80, 15/85, 10/90, and 0/100), which are viewed as having TI and/or -DPE-I-DPE-I- (II) “diads.” The I moieties (1,3-linked isomers) were always found to be incorporated in the crystals and acted as “entropy or symmetry” defects that effectively decreased the equilibrium melting temperature Tmo and the rate of crystallization. However, the retardation of crystallization in PEKK 0/100 (the homopolymer with pure II diads) was significantly less than expected, which was attributed to the segregation of I moieties between the chains leading to a reduction of total entropy in the unit cells. The evidence of segmental segregation in PEKK 0/100 was seen in x-ray diffraction patterns, where several extra reflections were seen that could only be indexed by the published unit cell modified with a larger c-axis dimension (3.048 nm, corresponding to the length of six phenyl residues or 1.524 nm, the length of three phenyl residues). The composition of 15/85 was found to have the lowest value of Tmo and the slowest crystallization rate. Upon heating, the “II” crystals (T/I from 30/70 to 0/100) exhibited the conventional double-melting behavior rather than the triple-melting behavior as in the “TI” crystals (50/50 to 40/60). No indication of the second polymorph form 2 was found in “II” crystals. © 1994 John Wiley & Sons, Inc.
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    Crystallization and thermal behavior of poly (vinylidene fluoride)/Poly[styrene-b-(Ethylene-co-butylene)-b-Styrene] blends functionalized with succinic groups (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 201-204 
    Details
    ISSN: 0887-6266
    Keywords: poly[styrene-b-(ethylene-co-butylene)-b-styrene] ; poly (vinylidene fluoride) ; miscibility ; crystallization ; melting ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No Abstract
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    Structural changes of silk fibroin membranes induced by immersion in methanol aqueous solutions (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 961-968 
    Details
    ISSN: 0887-6266
    Keywords: silk fibroin ; β structure ; crystallization ; molecular conformation ; glass transition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Structural changes of native and regenerated silk fibroin membranes were induced by immersion in water-methanol solutions and examined as a function of immersion time and methanol concentration. X-ray diffractometry and infrared spectroscopy data showed that transition from random coil to β-sheet structure occurred favorably when both native and regenerated silk fibroin membranes were immersed in water-methanol solutions, regardless of the different immersion time. Only native silk membrane, treated for 2 min with pure methanol, maintained its original amorphous structure, as demonstrated by differential scanning calorimetric (DSC) curves. The degree of displacement, measured by thermomechanical analysis (TMA), was much greater for regenerated than for native silk fibroin membranes. SDS-PAGE pattern showed that native silk fibroin has a molecular weight of 350, while the regenerated sample is formed by a large number of polypeptides in the range of 200-50 KD. The amount of acidic and basic amino acids decreased slightly in regenerated silk fibroin. Physical properties of silk membranes treated with water-methanol solutions are discussed in terms of membrane structure, treatment conditions, and chemical structure of starting material. © 1994 John Wiley & Sons, Inc.
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    Specific heat capacity and melting/crystallization characteristics of polytridecanolactone (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1999-2003 
    Details
    ISSN: 0887-6266
    Keywords: polytridecanolactone ; specific heat capacity ; melting ; crystallization ; transition enthalpy ; differential scanning calorimetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An investigation of the thermodynamical properties of polytridecanolactone (PTDL) was made with the aid of a differential scanning calorimeter (DSC). PTDL is a linear polyester and belongs to the polylactones, which have been poorly investigated. In this paper we contribute with specific heat capacity in the range 180-400 K, and melting and glass transition characteristics. Further, we present unique results corresponding to the effect of different cooling rates on crystallization temperatures and crystallization energies. PTDL has a melting temperature of 350 K, and a glass transition at about 237 K. The crystallization results show that PTDL crystallizes easily, with a crystallization degree of about 80%. In addition, the crystallization energy decreases with increasing cooling rate, and levels out at a constant value at higher cooling rates. The crystallization temperature, on the other hand, shows an increasing sensitivity of cooling rate, where the supercooling is increasing more rapidly at higher cooling rates. © 1994 John Wiley & Sons, Inc.
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    Thermal and X-ray investigations of ethylene-α-olefin copolymers obtained with highly active supported Ti-Mg and V-Mg catalysts (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 33 (1994), S. 111-114 
    Details
    ISSN: 0959-8103
    Keywords: copolymers ; ethylene ; α-olefins ; transition metal catalysts ; thermal stability ; crystallization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Copolymers of ethylene with propylene, butene-1 and hexene-1 were prepared using a titanium-magnesium (TMC) or a vanadium-magnesium catalyst (VMC). The copolymers were examined for thermal stability by TGA, melting and crystallization behaviour by DSC and crystallinity by XRD. Fractionated samples of ethylene-hexene-1 copolymers were also similarly characterized. Results indicate that VMC produces copolymers with a higher degree of crystallinity and greater compositional homogeneity than TMC.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1994.210330113
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    Whiskers of poly(3-alkylthiophene)s (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 735-742 
    Details
    ISSN: 0887-6266
    Keywords: poly(3-alkylthiophene) ; whiskers ; crystallization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that poly(3-alkylthiophene)s may readily crystallize from poor solvents in the form of whiskers. The experimental conditions required for the formation of whiskers were found to depend upon the alkyl side-chain length, solvent quality, and temperature. In all cases studied for alkyl side-chain lengths of 3-12 carbon atoms, the widths of the whiskers were of the order of 15nm, while their lengths often exceeded tens of microns. The thickness of the whiskers formed under the experimental conditions employed was found to scale with side-chain length, and was approximately 2 or 3 times the a/2 lattice dimension of the polymer unit cell. Packing of the macromolecules within the whiskers was such that the polymer backbones were normal to the whisker length; that is, the b-axis was oriented parallel to the long axis of the whiskers. These results are thought to be relevant to known thermochromism phenomena associated with poly(3-alkylthiophene)s. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310614
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  • 54
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    Self-nucleation and recrystallization of isotactic polypropylene (α phase) investigated by differential scanning calorimetry (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1383-1393 
    Details
    ISSN: 0887-6266
    Keywords: self-nucleation ; crystallization ; melting ; isotactic polypropylene ; thermal analysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystallization behavior after partial or complete melting of the α phase of iPP is examined by combined differential scanning calorimetry (DSC) and optical microscopy: calorimetric results are directly correlated with corresponding morphologies of microtome sections of DSC samples. On partial melting at various temperatures (hereafter referred to as Ts) located in a narrow range (4°C) below and near Tm, the number of nuclei increases (as in classical self-nucleation experiments), by several orders of magnitude; on subsequent cooling, the crystallization peak is shifted by up to 25°C. After partial melting in the lower part of the Ts range and recrystallization, the polymers display a prominent morphology “memory effect” whereby a phantom pattern of the initial spherulite morphology is maintained.After partial melting in the upper part of the Ts range the initial morphology is erased and self-nucleation affects only the total number of nuclei. The present experimental procedures make it possible to define, under “standard” conditions, the crystallization range of the polymer and in particular, the maximum crystallization temperature achievable when “ideally” nucleated. © John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311013
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    The effect of increased crystallization on the electrical properties of nylon-12 (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 265-271 
    Details
    ISSN: 0887-6266
    Keywords: Nylon-12 ; dielectric properties ; crystallization ; calorimetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dielectric properties of 30% crystalline dry Nylon-12 have been measured over the frequency range 10-105 Hz and temperature range 300-450 K, and the effect of its annealing at 423 K investigated both by dielectric measurement and differential scanning calorimetry. Annealing causes its crystallization to α phase, which increase the dc conductivity and decreases the contribution to orientation polarization, but does not alter the shape of the relaxation spectrum. The orientation polarization in Nylon-12 involves two processes, each of which occurs above the glass-transition temperature of Nylon-12, but only the spectra of the lowest temperature process could be clearly resolved. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310304
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    Glass transition, crystallization, and morphology relationships in miscible poly(aryl ether ketones) and poly(ether imide) blends (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 901-915 
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    ISSN: 0887-6266
    Keywords: poly(aryl ether ketones) ; poly(ether imide) ; crystallization ; melting ; glass transition ; morphology ; small-angle x-ray scattering ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The relationships among glass transition, crystallization, melting, and crystal morphology of poly(aryl ether ketone) (PAEK)/poly(other imide) (PEI) blends was studied by thermal, optical and small-angle x-ray scattering (SAXS) methods. Two types of PAEK were chosen for this work: poly(aryl ether ether ketone), PEEK, and poly(aryl ether ketone ketone), PEKK, which have distinctly different crystallization rates. Both PAEKs show complete miscibility with PEI in the amorphous phase. As PAEK crystallizes, the noncrystallizable PEI component is rejected from the crystalline region, resulting in a broad amorphous population, which was indicated by the broadening and the increase of Tg over that of the purely amorphous mixture. The presence of the PEI component significantly decreases the bulk crystallization and crystal growth rate of PAEK, but the equilibrium melting temperature and crystal surface free energies are not affected. The morphology of the PEI segregation was investigated by SAXS measurements. The results indicated that the inter(lamellar-bundle) PEI trapping morphology was dominant in the PEEK/PEI blends under rapid crystallization conditions, whereas the interspherulitic morphology was dominant in the slow crystallizing PEKK/PEI blends. These morphologies were qualitatively explained by the expression δ=D/G, where G was the crystal growth rate and D was the mutual diffusion coefficient. © 1993 John Wiley & Sons, Inc.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090310801
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    Self-nucleation and enhanced nucleation of polymers. Definition of a convenient calorimetric “efficiency scale” and evaluation of nucleating additives in isotactic polypropylene (α phase) (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1395-1405 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; nucleation ; nucleating additives ; isotactic polypropylene ; DSC ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A simple, convenient and reliable calorimetric efficiency scale is proposed for the evaluation of nucleating additives for polymers. The scale is based on conventional differential scanning calorimetry cooling runs and makes use of a crystallization range determined in self-nucleation experiments. It can be correlated with spherulite sizes, and indicates the potential range of improvement of nucleating additives. Typical nucleating agents for isotactic polypropylene are evaluated; at best they rate at 60 to ca. 70% on this efficiency scale. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311014
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    Self-nucleation and recrystallization of polymers. Isotactic polypropylene, β phase: β-α conversion and β-α growth transitions (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1407-1424 
    Details
    ISSN: 0887-6266
    Keywords: isotactic polypropylene ; β phase ; α nucleation ; melting ; crystallization ; growth transitions ; thermal analysis ; morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanisms which, in isotactic polypropylene, create α phase nuclei on partial melting of β phase spherulites are investigated by thermal analysis and optical and electron microscopy. Nuclei concentrations are determined from recrystallization characteristics. α phase nuclei are formed within β spherulites via two different mechanisms: (1) a low temperature formation of latent α phase nuclei (αβ* nuclei) linked with a hitherto unsuspected β to α growth transition at T = T* ∼ 105°C, and (2) a high temperature α phase nucleation process (αβ nuclei), also linked with a similar β to α growth transition at 140°C first reported by Varga et al. The low temperature nucleation mechanism is the more efficient one: it significantly affects the melting of β phase, and results in samples with over 1013 α nuclei · cm-3. © 1993 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311015
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  • 59
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    Compatibility and crystallization in poly(ethylene oxide)-poly(methyl methacrylate) semi-interpenetrating polymer network (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1627-1639 
    Details
    ISSN: 0887-6266
    Keywords: semi-IPN ; crystallization ; phase separation ; compatability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Differential scanning calorimetry together with dynamic mechanical analysis were employed to investigate the crystallinity and the miscibility in poly(ethylene oxide)/crosslinked poly(methyl methacrylate) semi-IPN (interpenetrating polymer networks). The crystallinity of poly(ethylene oxide) in the semi-IPN is found to depend on the crosslink density of PMMA as well as the overall content of PEO. Of special interest is that an increase in the crosslink density tends to increase the crystallinity contrary to our expectation, indicating crystallization and phase separation may proceed simultaneously during IPN formation. The investigation of glass transition behaviors with dynamic mechanical analysis suggests phase separation (i.e., there exist two amorphous phases: one PEO-rich phase, the other a PMMA-rich phase). © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311119
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    Crystallization of isotactic polypropylene and high-density polyethylene under negative pressure resulting from uncompensated volume change (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1285-1291 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; isotactic polypropylene ; high-density polyethylene ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The melting behavior of spherulites in thin sections of isotactic polypropylene bulk samples and high-density polyethylene thin films crystallized isothermally at various temperatures has been studied by polarized light microscopy. The regions around cavities and multiple boundary points between spherulites have higher melting temperatures than the other parts of spherulites crystallized in Regime III. The increase in melting temperature is explained as a result of crystallization under negative pressure arising locally in pockets of occluded melt due to density change during spherulitic crystallization. The negative pressure lowers locally the equilibrium melting temperature and therefore decreases the undercooling, which results in an increase in lamellar thickness. Sectioning of bulk samples releases frozen negative pressure and reveals the increase in melting temperature of those parts of spherulites that were crystallized at lower undercooling. © 1993 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311003
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