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  • 1
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The insertion of oligo(tetraflouroethene) segments into the main chain of poly(aramide)s and poly(amide imimide)s is accompanied by a decrease of the glass temperature. The decrease is strictly related to the number of CF2-units and is the same for both poly(aramide)s and poly(amide imide)s. The absolute glass temperature depends, however, on the initial structures of the monomeric units. As a consequence ‘mastercurves’ can be constructed by shifting the individual Tg vs. number of CF2-units curves along the temperature axis. A detailed analysis of the data indicates that besides the Tg-mass/‘flexible’ bond of monomeric unit criterion additional volume and interaction dependant packing effects have to be considered for an accurate prediction of the glass temperatures of polymers.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 273 (1995), S. 661-674 
    ISSN: 1435-1536
    Keywords: Saccharide-based amphiphiles ; 4-alkyl-semicarbazones ; gelation of saccharide-amphiphiles ; self-organization ; supramolecular organization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The synthesis of 4-alkyl-semicarbazones derived from reducing sugars and semicarbazides is presented as a convenient route for the preparation of amphiphilic saccharides. This semicarbazone route allows to employ a large variety of reducing sugars as hydrophilic building block for saccharide tensides. The preparation of two series of amphiphiles based on D-maltose with non-methylated and mono-N-methylated semicarbazone units is described. Then-alkyl chains were varied fromn-octyl ton-hexadecyl. Various maltotriose derivatives have also been prepared. Critical micelle concentration (CMC) as well as critical gel concentration of the derivatives were studied in dependence of then-alkyl chain length. Both values decreased with increasing length of then-alkyl chain. Self-organization of the gels was studied by transmission electron microscopy of freeze-fractured samples. Due to the supramolecular organization of the amphiphiles, the gels consisted of twisted rope-like molecular assemblies with the same helical twist sense. The helical pitch depended on the hydrophilic/lipophilic balance. In contrast to gels onn-alkylgluconamides, the gels were formed in dilute aqueous solution and exhibited striking longevity without additional stabilization by surfactants. In the solid, the amphiphiles exhibited thermotropic transitions to partially disordered mesophases.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Different scanning force microscopy (SFM) modes were applied for the examination of drawn films of isotactic and syndiotactic polypropylene, iPP and sPP. Uniaxially stretched films with a draw ratio λ=6 were studied at ambient conditions, and under water. In iPP films striated patterns of 40–50 nm in width, which are oriented along the stretching direction, exhibit shish-kebab morphology. The dominating nanoscale features are nanofibrils of 10–15 nm in width, and lamellar platelets, which are 40–50 nm in width and 30–35 nm in length. In many places lamellar platelets are closely packed, and they form periodical sequences with a repeat distance of 30–35 nm, which is consistent with thelong period. Similar and differing morphological features were found comparing the images of iPP and sPP films. Extended fibrillar patterns of sPP exhibit similar width in the 40–50 nm range, while the lamellar structure is more compact, and the platelets are less uniform in length than those in iPP. The length of lamellar platelets ranges from 30 to 60 nm, and they form local periodical patterns.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 34 (1995), S. 301-308 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Upon heating above its melting temperature at 195°C, 2-(4-hydroxyphenyl)-1,3-oxazoline (HPO) was polymerized thermally in melt phase within a few minutes to produce a polymer with etheramide and N-4-hydroxybenzoyl-ethyleneimine repeat units. Polymerization in solution afforded only oligomers with 93% etheramide structure after several hours. Reactive blending, combining 2-phenyl-1,3-oxazoline (PO) grafting with in-situ HPO thermal polymerization in poly(ethene-co-methacrylic acid), was the key to novel self-reinforced multiphase ethene copolymer blends containing spherical dispersed poly(HPO) microphases. Poly(HPO) microstructures, blend morphologies, thermal and mechanical properties were investigated.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A metallocene-based isotactic polypropylene (m-iPP) was blended with various types of ethene-co-butene rubbers (EBR). Blend miscibility was examined by means of dynamic mechanical analysis (DMTA). In addition, morphology was studied on cyclohexane etched cryofractured samples. Stiffness and toughness properties were assessed and interpreted in function of the blend miscibility. Izod tests served for the dynamic fracture toughness characterization. The essential work of fracture (EWF) approach was used for the characterization of the static fracture toughness. It was found that the 1-butene content of the EBR strongly affects the blend miscibility. A disperse structure was found as prerequisite for outstanding overall toughness. When distiguishing between resistance to crack initiation and propagation, it was found that they are changing adversely to one another.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 735-740 
    ISSN: 0887-624X
    Keywords: homogeneous Ziegler-Natta polymerization ; metallocenes ; ethene/1-octene copolymerization ; copolymerization parameters ; influence of the temperature and solvent ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethene was copolymerized with 1-octene using homogeneous MAO-activated rac-Me2Si(2-MeBenz[e]Ind)2ZrCl2 at constant ethene concentration with temperature varying between 0 and 60°C to determine a temperature dependence of copolymerization parameters. At constant 1-octene and ethene concentration (constant ethene/1-octene feed molar ratio) 1-octene incorporation decreased with increasing temperature. Furthermore, when ethene/1-octene molar ratio was varied by varying the temperature keeping 1-octene concentration and ethene pressure constant, increasing temperature accounted for lower molecular masses without affecting 1-octene incorporation. An explanation for the observed temperature dependence of the copolymerization parameters is presented, considering the solution-enthalpy of the gaseous ethene in the solvent. In all cases amorphous poly(ethene-co-1-octene) with 1-octene content varying between 20 and 40 mol % was obtained. © 1997 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 815-826 
    ISSN: 0021-8995
    Keywords: 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: Mechanical and fracture mechanics properties of transparent multiphase epoxy resins toughened with various amounts of compatibilized silicone liquid rubbers consisting of polycaprolactone-block-poly(dimethylsiloxane)-block-polycaprolactone triblock copolymer have been investigated. At silicone liquid rubber contents 〈 10 wt % significantly improved toughness has been achieved without adversely affecting thermal and mechanical properties. Fractographic and interferometric methods have been applied to study crack propagation in such silicone-modified resins. © 1994 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 1799-1806 
    ISSN: 0021-8995
    Keywords: 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: Glass bead-reinforced isotactic polypropene hybrid composites containing 0-20 vol % thermoplastic elastomers were prepared to study both structure/property relationship and morphology development. Polystyrene-block-poly(ethene-co-but-1-ene)-block-polystyrene (SEBS) and the corresponding block copolymer grafted with maleic anhydride (SEBS-g-MA) were used as thermoplastic elastomers. Hybrid composites containing SEBS gave higher Young's moduli than did those containing SEBS-g-MA. The experimental Young's moduli were in good agreement with the theoretical predictions according to Lewis and Nielsen. The lower moduli of hybrid composites containing SEBS-g-MA were attributed to interlayer formation and in situ encapsulation of glass beads, resulting in core-shell particles. This elastomeric interlayer impaired the filler reinforcement. Analysis of tensile yield stress and results of lap-shear tests confirmed strong filler-polymer interactions in composites containing SEBS-g-MA. Only in excess of a critical volume fraction did SEBS-g-MA afford a significant improvement of the notched Izod impact strength. In contrast to stiffness, Izod impact strength was not influenced by the type of elastomer and morphology. Investigation of crystallization and scanning electron microscopic studies proved the in situ encapsulation of the glass beads with SEBS-g-MA, whereas SEBS addition results in separately dispersed glass beads and SEBS microphases. © 1996 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 40 (1998), S. 337-344 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract. Random copolymers of ethene with 1-octene were investigated by means of pressure-volume-temperature (PVT) measurements. Solubility parameters were calculated from the thermal expansion coefficients and isothermal compressibilities. While expansion coefficients are virtually independent of 1-octene content, compressibilities decrease with increasing 1-octene incorporation. The solubility parameters varied between 17.3 and 15.2 MPa1/2 when 1-octene incorporation was varied between 2 and 100 wt%. In the framework of the solubility parameter concept copolymers containing less than 95 wt% 1-octene were shown to be immiscible with isotactic poly(propene).
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 43 (1999), S. 395-402 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Thermal and mechanical properties of poly(methylmethacrylate-co-dodecylmethacrylate) nanocomposites based upon exfoliated organophilic layered silicates, were investigated as a function of the silicate and comonomer content. Layered silicates such as sodium bentonite were rendered organophilic by means of ion-exchanging sodium cations for N,N,N,N-dioctadecyl-dimethyl-ammonium cations. Silicate exfoliation was enhanced by means of 5 and 10 wt.-% dodecyl-methacrylate (LMA) addition to afford translucent reinforced acrylic nanocomposites. In contrast to conventional filled acrylic polymers, only 10 wt.-% organophilic silicate was sufficient to increase Young's modulus from 2200 to 4030 MPa, glass temperature from 72 to 80 °C and degradation temperature from 220 to 256 °C with respect to the neat MMA/LMA (90 wt.-%/10 wt.-%) copolymer. Flammability studies, performed on a cone calorimeter, revealed that the maximum heat release rate of MMA/LMA copolymer nanocomposite decreased from 837 kW/m2 to 566 kW/m2. The nanocomposite morphology was examined by means of transmission electron microscopy (TEM).
    Type of Medium: Electronic Resource
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