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  • Chemistry  (6)
  • 2005-2009
  • 1990-1994  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Fourier transform infrared spectroscopy of the polymorphic forms of syndiotactic polystyrene (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 2111-2119 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Infrared spectra of syndiotactic polystyrene exhibiting various crystalline forms and modifications, and in the amorphous state, are reported in this contribution. In addition to strong conformational effects, the spectra demonstrate striking effects of chain packing. Several infrared spectral differences also exist between the two crystalline forms which present a trans-planer conformation of the chains. Spectral changes are also reported for solution-crystallized samples, which depend on the solvent present in the clathrate compound formed with the polymers.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910914
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal, dielectric, and mechanical relaxation in poly(benzimidazole)/poly(etherimide) blends (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 649-657 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal, dielectric, and mechanical relaxation measurements on miscible blends of polybenzimidazole (PBI) and a polyetherimide (PEI, Ultem 1000) prepared by solution casting from dimethylacetamide (DMAc) reveal a number of structurally related features. Annealing below the glass transition temperature induces an enthalpy relaxation process typical of single-phase glasses of nonequilibrium structure. Dielectric relaxation experiments on samples annealed at ambient conditions reveal two relaxation processes below 400°C. At lower temperatures (50-200°C), the desorption of water is observed. Above 200°C in the first run, a composition-dependent relaxation is seen at the highest frequencies (100 kHz) while a relaxation approximately independent of composition appears in the second run. The latter corresponds to the glass transition of the PEI phase. The glass transition of PBI at this frequency is above the degradation temperature. At lower frequencies a strongly dispersive electrode polarization process masks the high-temperature relaxations. Dynamic mechanical results show similar features with respect to phase separation; the main difference is that the tan δ curves in the first run are complicated by the desorption of residual solvent.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090290602
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal degradation of segmented polyurethanes (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1087-1095 
    Details
    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: Thermal degradation of polyurethane samples was studied by a thermogravimetric method. The effect of soft-segment length and soft-segment concentration on activation energy of the degradation process was measured. Three methods of calculation gave activation energies at different stages of the very complex weight loss process. It was shown that at initial stages of the weight loss the process was dominated by hard-segment degradation. Activation energy of the whole process calculated by the Ozawa-Flynn method did not offer clear insight into the structure-stability relationship of polyurethanes. The second method showed that activation energy of the initial stage of degradation increased with decrease in hard-segment length. The Flynn method of calculating activation energy produced fairly constant activation energy of the first 40% degradation, at around 150 kJ/mol, for polymers in the C series. Generally, calculation of kinetic parameters of a complex degradation process as in polyurethanes gives results that are not easy to interpret. It has been shown qualitatively that polymers with higher soft-segment concentration display lower initial weight loss and higher onset temperatures of degradation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510615
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  • 4
    Electronic Resource
    Electronic Resource
    Miscibility in blends of sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) and poly(p-bromostyrene-co-o-bromostyrene) (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1499-1503 
    Details
    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: Miscibility in blends of random copolymers of p-bromostyrene (pBrSt) and o-bromostyrene (oBrSt) [P(pBrSt-co-oBrSt)] with partially sulfonylated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) have been studied by differential scanning calorimetry (DSC). For an SPPO of given degree of sulfonylation, a miscibility window in terms of the isomeric composition of the brominated copolymer was seen; the location and width of the window was a function of sulfonylation. In general, copolymers with a higher content of pBrSt exhibit miscibility with SPPOs with higher degrees of sulfonylation. Upon annealing to temperatures of 280° and 320°C, only small changes in the miscibility regime were observed. The miscibility behavior was analyzed on the basis of the mean-field theory in terms of the individual segmental interaction parameters. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070521014
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  • 5
    Electronic Resource
    Electronic Resource
    Phase behavior in copolymer blends of poly (p-chlorostyrene-co-o-chlorostyrene) and phenylsulfonylated poly (2,6-dimethyl-1,4-phenylene oxide) (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1079-1087 
    Details
    ISSN: 0887-6266
    Keywords: Miscibility ; copolymers ; isomeric effects ; halostyrenes ; phenylene oxide polymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The miscibility of random copolymers of o-chlorostyrene and p-chlorostyrene [P (oClSt-co-pClSt)] with partially phenylsulfonylated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO) copolymers has been studied, using differential scanning calorimetry (DSC) to establish Tg behavior. It already has been established that the isomeric effect of the chlorine substitution on miscibility is large. Thus the para-chloro-substituted styrenic homopolymer is miscible with all SPPOs containing more than ∼ 5 mol % phenylsulfonylation, whereas the ortho-chloro-substituted homopolymer is immiscible with the entire range of SPPO copolymer compositions (and also with the respective homopolymers). As a result of this asymmetric behavior of the homopolymers, the width of the window of miscibility in blends now investigated containing copolymers with high pClSt content and SPPO is much greater than in the corresponding blends containing copolymers with large mole fraction of oClSt. These differences are reflected in the corresponding χ parameters calculated from analysis of the data. It was also found that the miscibility is temperature dependent and that the regime in the copolymer-copolymer composition plane shrank as the equilibrium temperature increased, results indicative of LCST behavior. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320612
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  • 6
    Electronic Resource
    Electronic Resource
    Miscibility and crystallization kinetics in blends of poly(ethylene terephtalate) and thermotropic liquid crystal polyesters (1992)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 383-388 
    Details
    ISSN: 1042-7147
    Keywords: Crystallization kinetics ; Polymer blends ; Poly(ethylene terephtalate) (PET) ; thermotropic liquid crystal polyester (TLCP) ; 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
    Notes: Binary blends of poly(ethylene terephtalate) (PET) and thermotropic liquid crystal polyester (TLCP) have been prepared by both solution and melt blending methods. The TLCPs utilized were Vectra (Hoechst Celanese), TR-4, a TLCP synthesized in our laboratory, and a block copolymer consisting of three TR-4 units followed by three PET units. The phase behavior of the blends was studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and optical microscopy. The results show that none of the blends is miscible, but significant interactions exist between the PET phase and the TLCP phase in the case of TR-4 and TR-4 block copolymer blends. These interactions lead to a different nucleation mechanism in these blends compared to that in PET/Vectra.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pat.1992.220030703
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