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  • 31
    Electronic Resource
    Electronic Resource
    Solubility of thermotropic polybibenzoates with oxyethylene spacers (1991)
    Springer
    Polymer bulletin 25 (1991), S. 413-418 
    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 Three polybibenzoates with two, three and four oxyethylene units in the spacer have been synthesized in order to analyze the influence of the length of the spacer on the stability of the mesophase and on the solubility behaviour. It was found that the thermal stability of the mesophase decreases as the length of the spacer increases, in such a manner that an amorphous polymer is obtained when four oxyethylene units are involved. On the other hand, although the value of the solubility parameter is little affected by the spacer, the solubility range is significantly widened by an increase in the number of oxyethylene units. Optimal characteristics are displayed by the polyester with three such units in the spacer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00316914
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  • 32
    Electronic Resource
    Electronic Resource
    Partial specific volume of thermotropic polybibenzoates with different spacers (1993)
    Springer
    Polymer bulletin 31 (1993), S. 111-115 
    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 Partial specific volume (v 2 o ) of polybibenzoates with all-methylene and oxyethylene spacers have been determined in chloroalifatic solvents. The polybibenzoate with a heptamethylene spacer exhibits a more expanded state than the ones with one, two and three oxyethylene units in the spacer. A solvent effect on v 2 o has been observed. Nevertheless, the values of v 2 o in tetrachloroethane are in accord with the calculated by group contributions from rubbery polymers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298772
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  • 33
    Electronic Resource
    Electronic Resource
    Microhardness and DSC measurements on liquid crystalline poly(diethylene glycolp,p′-bibenzoate) as a function of the ageing time (1992)
    Springer
    Polymer bulletin 29 (1992), S. 233-237 
    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 ageing process of the liquid crystalline glass of poly(diethylene glycolp,p′-bibenzoate), PDEB, has been studied by differential scanning calorimetry and microhardness measurements. The experiments have been performed on a sample of PDEB aged at 36±C during different times. The process was found to be rather fast at that temperature, and the results from both techniques are compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00558062
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  • 34
    Electronic Resource
    Electronic Resource
    Crystallinity and thermal properties of ethylene-1-decene copolymers (1993)
    Springer
    Polymer bulletin 31 (1993), S. 89-95 
    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 Three copolymers of ethylene and 1-decene, covering a wide range of compositions, have been synthesized with a MgCl2-supported Ziegler-Natta catalyst. The analysis by DSC and X-ray shows a great degree of heterogeneity in these copolymers and appreciable levels of crystallinity, corresponding to the orthorhombic lattice of polyethylene, are present even for very high 1-decene contents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298769
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  • 35
    Electronic Resource
    Electronic Resource
    Sulphuric acid etching of polyethylene surfaces (1985)
    Springer
    Journal of materials science 20 (1985), S. 3283-3288 
    Details
    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 The sulphuric acid etching of polyethylene results in the formation of sulphonic groups, varying the surface properties. The study of the groups formed during the etching has been carried out by means of frustrated multiple internal reflection infrared spectroscopy (FMIR). Densities, thermal properties, superficial resistances and resistivities have been correlated with the content of sulphonic groups and treatment time. Moreover, the critical surface tension and platelet adhesion have been examined and related with the change in those properties. Direct sulphonation of polyethylene is a suitable method to change its surface properties, improving the application of this polymer as a biomaterial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545196
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  • 36
    Electronic Resource
    Electronic Resource
    Analysis of the activation energy spectrum for the enthalpy relaxation of a glassy liquid crystalline polymer (1997)
    Springer
    Journal of materials science 32 (1997), S. 3601-3605 
    Details
    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 The phenomenology of the physical ageing of glassy materials can be described by using the activation energy spectrum model. This model was originally developed for relaxations in metallic and oxide glasses and this paper applies it to a liquid crystalline polymer, poly(diethylene glycol p, p′-bibenzoate) (PDEB), in the glassy state. PDEB samples were quenched from above Tg and isothermally annealed in a differential scanning calorimetry (DSC) equipment, and a description of the enthalpy relaxation of PDEB was achieved by means of the Kohlrausch–Williams–Watts (KWW) equation. The results show that the relaxation time decreases when the annealing temperature increases and can be explained in terms of an Arrhenius-type equation. The predicted value for the apparent activation enthalpy (0.98 eV) is lower than those reported for other polymers. This approach assumes that a unique elemental process with a relaxation time τ0=1.3×10-13 min controls the evolution of the system. Energy spectra demonstrate that the activation energy values for the mechanisms controlling the relaxation are lower than 1.1 eV and the spectra present a maximum for an activation energy close to 0.98 eV. The total number of available relaxation processes (measured by the area below the curves) decreases if the sub-Tg annealing temperature increases. Moreover, the results show that the distributions widen if the shape parameter of the KWW equation decreases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018622228143
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  • 37
    Electronic Resource
    Electronic Resource
    Temperature dependence of microhardness indentations and dynamic mechanical moduli of polyesters in the vicinity of the glass transition (1989)
    Springer
    Journal of materials science 8 (1989), S. 1418-1419 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00720208
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  • 38
    Electronic Resource
    Electronic Resource
    Rock mass characterization by laboratory and field testing (1988)
    Springer
    Geotechnical and geological engineering 6 (1988), S. 91-95 
    Details
    ISSN: 1573-1529
    Keywords: Rock characterization ; field testing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00880800
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  • 39
    Electronic Resource
    Electronic Resource
    Effect of crystallization conditions on the morphological structure of ethylene-1-butene copolymers obtained by different ziegler-natta catalyst systems (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 1189-1193 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Four ethylene- 1 -butene copolymers of about the same comonomer content but obtained with different supported Ziegler-Natta catalyst systems have been studied. The effects of the catalyst and the crystallization conditions on the morphological structure have been analyzed. These two factors'clearly affect the melting endotherms and the most probable crystallite thickness of the copolymers, although no important differences were found in the crystalline contents. The catalyst system influences the melting pattern due to changes in the chemical composition distribution, i.e., variations in the comonomer content between chains of different molecular weight.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760311606
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  • 40
    Electronic Resource
    Electronic Resource
    The glass transition in linear low density polyethylene determined by thermally stimulated depolarization currents (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 641-648 
    Details
    ISSN: 0887-6266
    Keywords: polyethylene ; glass transition ; TSDC ; γ transition ; β transition ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New thermally stimulated depolarization currents (TSDC) results on LLD polyethylene functionalized with diethylmaleate polar groups are precisely computer fitted with the direct signal analysis technique. It is shown that the TSDC spectrum consists, with increasing temperatures, of a sub-γ peak, a sharp γ peak, and a β and an α relaxation. The first peak is analyzed in terms of Arrhenius relaxation times, whereas the γ and β transitions could only be fitted by using Vogel-Fulcher temperature dependence for the relaxation times. The best value for To obtained from both fittings is 69.7 K. This is a quantitative proof for the identification of the γ transition as one of the dielectric manifestations of the glass-rubber transition for polyethylenes, Tg = 136.5 K, which has been discussed extensively in the literature. The β relaxation, Tgβ = 237 K, has also the expected characteristic of a glass transition; the existence of two Tgs in polyethylene could explain our results. © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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