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  • 1
    Electronic Resource
    Electronic Resource
    A DSC study of oriented samples of a blend of linear and branched polyethylene (1981)
    Springer
    Polymer bulletin 4 (1981), S. 717-723 
    Details
    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 Differential scanning calorimetry (DSC) of cold-drawn samples of a blend of linear (LPE) and branched polyethylene (BPE) shows that the melting point of the high temperature peak decreases monotonically with increasing draw ratio. This is in apparent contradiction to the data obtained for pure LPE, for which quite unanimously the melting point has been shown to increase with increasing draw ratio. An explanation of this deviation in behaviour between the blend of LPE and BPE and the pure LPE is proposed based on the idea that the transformation of the lamellar structure to a fibrillar structure involves several kinds of rearrangement including a mixing on a supermolecular level of the originally segregated LPE and BPE components. The crystal rearrangements occurring on heating (in the DSC) in oriented pure LPE that are responsible for the high melting point of this system are thereby hindered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285139
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and characterization of poly(11-(4′-cyano-trans-4-stilbenyloxy)undecanyl vinyl ether) (1992)
    Springer
    Polymer bulletin 28 (1992), S. 267-274 
    Details
    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 Polymers based on 11-(4′-cyano-trans-4-stilbenyloxy)undecanyl vinyl ether have been synthesized by living cationic polymerization, photo-initiated cationic polymerization using onium salts and thermal initiated cationic polymerization using onium salts. The polymers have been characterized by size exclusion chromatography, nuclear magnetic resonance spectroscopy, differential scanning calorimetry and polarized light microscopy. Living cationic polymerization resulted in a polymer of low molecular mass Mn≤3 600, with a uniformity index (D) of 1.2 displaying a focal conic texture indicative of smectic A (sA) phase with preserved cyanogroup and trans-configuration. Photo-initiation using 2,4,6-trimethylbenzoylethoxyphenylphosphine oxide and diphenyliodonium hexafluorophosphate resulted in an insoluble polymer exhibiting only vague liquid crystalline textures. Initiation with phenothiazine and phenacyltetramethylenesulfonium hexafluoroantimonate also yielded a partly insoluble polymer with a disturbed sA phase. It is suggested that the monomer and polymer are sensitive towards radicals leading to cross-linking and branching. The thermal initiation on systems with α-methylbenzyltetramethylenesulfonium hexafluorophosphate and p-methoxybenzyltetramethylenesulfonium hexafluorophosphate resulted in completely soluble mesomorphic polymers of Mn≤13 000, D=1.7 and Mn≤26 000, D=2.8 respectively, in both cases with a preserved cyanogroup and a transconfiguration. Polarized light microscopy revealed a distinct focal conic structure indicative of sA in both cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294821
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  • 3
    Electronic Resource
    Electronic Resource
    Morphology of linear PE blends crystallized at the transition temperature between regime I and regime II growth (1989)
    Springer
    Polymer bulletin 22 (1989), S. 277-284 
    Details
    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 Binary blends of linear PE sharp fractions [Mw=2 500 (L2.5) and 66 000 (L66)], all crystallized at the temperature of the transition between regime I and regime II growth, have been studied by TEM after Kanig treatment. It is shown that the dominant lamellae are always long and straight and form stacks. The number of lamellae in these stacks decreases with increasing content of L2.5. The lamellar width perpendicular to [010] is 1–3 μm for L66 and the 50/50 blend, but anomalously high for the 80/20 (L2.5/L66) blend. Thin subsidiary lamellae are observed only in the 50/50 and 80/20 blends. A significant fraction of these samples contains domains of segregated L2.5 showing no lamellar contrast.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00282853
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical degradation of polymers of styrene and substituted styrenes. 2 (1993)
    Springer
    Polymer bulletin 31 (1993), S. 61-68 
    Details
    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 substituted styrene monomers (p-amino styrene (p-AS), p-dimethylamino styrene (p-DMAS), p-trifluoromethyl styrene (p-TFMS), p-phenoxy styrene (p-PhOS), p-benzyloxy styrene (p-BeOS) and p-chloromethyl styrene (p-CIMS)) were copolymerized with styrene. Homopolymers were produced of monomers p-PhOS and p-butoxy styrene (p-BuOS). Thin films of the polymers were subjected to external partial discharges in air and the time to breakdown was measured. The stability of the polymers towards partial discharges is discussed with reference to radical formation and segmental mobility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298765
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  • 5
    Electronic Resource
    Electronic Resource
    Relaxation processes in hyperbranched polyesters (1994)
    Springer
    Polymer bulletin 32 (1994), S. 679-685 
    Details
    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 Dielectric permittivity and loss have been measured over the frequency range 10-2 Hz-10 kHz between 100 K and 350 K for samples of 50/50 mixtures of each of two hyperbranched polyesters, one five-generation hydroxy functional (5G-OH) and one threegeneration alkyl-terminated polymer (3G), with dielectrically inactive linear polyethylene. The thermal transitions of the hyperbranched polymers were studied with differential scanning calorimetry. Three relaxation transitions were found in 5G-OH: α, the glass-rubber transition and two subglass processes denoted β and γ showing Arrhenius temperature dependence both with an activation energy of 96±2kJ mol-1. The low temperature process could be assigned to motions of the terminal hydroxyl groups whereas β is due to reorientation of the ester groups. Sample 3G showed only a glass transition and one subglass process being assigned to reorientation of the ester groups. The high activation energy (202 kJ mol-1) of this process indicates that the ester groups are highly constrained in this polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973919
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  • 6
    Electronic Resource
    Electronic Resource
    Photoinitiated cationic bulk polymerization of mesogenic vinyl ethers (1991)
    Springer
    Polymer bulletin 25 (1991), S. 641-648 
    Details
    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 Mesogenic vinyl ethers have been bulk polymerized cationically in the liquid crystalline phase, using onium salt redox systems for photochemical initiation. High molecular mass polymers (Mn≤41 000) with a narrow molecular mass distribution (around 2) were obtained at high temperatures (≤80°C). Apparently the polymerization system stabilizes the propagating cation and thus reduces the tendency for chain transfer to occur. Highly ordered thin (30–50 μm) films were produced by the polymerization of monomers oriented in their nematic phase. Despite the fact that they were in the sA phase, the films were completely transparent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01032659
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  • 7
    Electronic Resource
    Electronic Resource
    Kinetics of isotropic-smectic phase transitions in a liquid-crystalline polyether with a methylene spacer of 12 carbons (1991)
    Springer
    Polymer bulletin 27 (1991), S. 315-322 
    Details
    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 isotropic-smectic (sB or sG) mesophase transition in a thermotropic main chain polyether based on bis(4-hydroxyphenoxy)-p-xylene with a methylene spacer having 12 carbons has been studied by polarized light microscopy and differential scanning calorimetry. The apparently nucleation-controlled transition followed the general Avrami equation with an exponent value between 2.5 and 3.2. The smectic domains grow more rapidly along the chain axis than in the perpendicular direction. The growth rate exhibited the following temperature (T) dependence: $$G = G_0 \exp \left( {\frac{{ - Kg}}{{T(T^ \circ _i - T}}} \right)$$ where Go and Kg are constants and To i is the equilibrium clearing temperature. A second Arrhenius-activated process was evident at high temperatures. The data presented in this paper are critically compared with data previously reported for similar main-chain polyethers with methylene spacer groups having 9 and 11 carbons in order to reveal possible odd-even effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00294538
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  • 8
    Electronic Resource
    Electronic Resource
    Miscibility assessment and thermal oxidative stability of blends of branched polyethylene and poly(1,2-butadiene) (1994)
    Springer
    Polymer bulletin 32 (1994), S. 687-692 
    Details
    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 Poly(1,2-butadiene) promotes crosslinking of branched polyethylene, which indeed indicates partial miscibility of the two polymers. Dynamic mechanical spectroscopy and transmission electron microscopy of blends of branched polyethylene and poly(1,2-butadiene) indicated that the polymers are partially immiscible even in the blend with only 3% of poly(1,2-butadiene). The thermal oxidative stability at temperatures above the melting point of samples stabilized with antioxidants was essentially unaffected by the percentage concentration of poly(1,2-butadiene), whereas the stability towards external partial discharges was lower in crosslinked polyethylene blends containing poly(1,2-butadiene) than in pure crosslinked polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973920
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  • 9
    Electronic Resource
    Electronic Resource
    Observations of shish-kebabs in solvent-treated fracture surfaces of polyethylene (1983)
    Springer
    Polymer bulletin 9 (1983), S. 85-89 
    Details
    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 Shish-kebabs are observed by scanning electron microscopy on fracture surfaces of a low molecular weight, high-density polyethylene treated by hot pxylene. The shish-kebabs observed originate from the fibrils of the fracture surface. It is suggested that the larger fibrils are partially dissolved and that the partially dissolved molecules recrystallize on cooling forming the lamellar-like structures of the shish-kebabs. The less developed fibrils of the fracture surface dissolve completely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00275573
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  • 10
    Electronic Resource
    Electronic Resource
    Microscopic observations relating fracture morphology to molecular weight segregation in melt-crystallized polyethylene (1983)
    Springer
    Polymer bulletin 9 (1983), S. 90-97 
    Details
    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 Fractography by scanning electron microscopy (SEM) of samples of a low molecular weight, high-density polyethylene from the melt isothermally crystallized at 125°C, together with SEM on these samples treated with p-xylene (including fracture surfaces), polarized light microscopy, differential scanning calorimetry and gel permeation chromatography have provided evidence that fracture preferentially develops along a weakest link path defined by regions of segregated low molecular weight material. The segregated material is to a considerable extent accumulated in the spherulite boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00275574
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