Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1990-1994  (7)
  • 1980-1984  (4)
  • Polymer and Materials Science  (9)
  • crystallinity  (2)
Source
Material
Years
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Radiation-induced crosslinking: II. Effect on the crystalline and amorphous densities of polyethylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 469-476 
    Details
    ISSN: 1435-1536
    Keywords: Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; d-spacings ; phase densities ; crosslink locations and mechanisms ; defects ; lateral grain boundaries
    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 Small-angle x-ray scattering (SAXS) was used to determine the structural changes in polyethylene induced by radiation. The changes in densities of the crystalline and amorphous phases, ρ c and ρ a , were calculated after direct determination of the mean square density fluctuation 〈η2〉. ρ a increases with increasing radiation dose for both linear and branched polyethylene. This accounts for the serious discrepancy between crystallinities determined from wide-angle x-ray scattering and density measurements. This study confirms our previous proposal that crosslinks occur primarily in the noncrystalline phase, most likely at the defects in the lateral grain boundary regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655884
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Radiation-induced crosslinking: III. Effect on the crystalline and amorphous density fluctuations of polyethylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 353-363 
    Details
    ISSN: 1435-1536
    Keywords: Crosslinking ; radiation ; polyethylene ; density ; crystallinity ; phasedensities ; densityfluctuation ; phasedensityfluctuations ; Crosslink locations and mechanisms ; defects ; lateral grainboundaries
    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 Small-angle x-ray scattering (SAXS) was used to determine density fluctuation in radiation-induced crosslinked polyethylene of varying degrees of crystallinity. Density fluctuation FL decreases with increasing crystallinity, while it increases linearly with increasing radiation dose or degree of crosslinking. By means of extrapolation, density fluctuations in the crystalline and the amorphous phasesFL c andFL a were obtained. At a given dose,FL a is greater thanFL c . The increase inFL a with radiation is found to be much greater than that ofFL c compared with the initial values at 0 Mrad,FL c showing only a negligible increase event at 312 Mrad. The present findings suggest that crosslinks are not introduced within the crystalline phase; they take place primarily in the noncrystalline phase, in agreement with the conclusions reached previously on the basis of changes in crystalline and amorphous densities in irradiated polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654582
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and chemo-physical properties of hydrogels (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 196 (1992), S. 49-61 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Hydrogele wurden aus methylmethacrylat (MMA) and N-Vinyl-2-pyrrolidon (NVP) mit 1,2,2-Trimethylolpropantrimethacrylat (TPTA) als Vernetzungsmittel hergestellt. Die Terplymerisation wurden mittels UV-strahlung (365 nm) initiiert, wobei kleine Mengen an Diethoxycetophenon (DEAP) als Photosensibilisator sowie Triethanolamin(TEA)als Beschleuniger und Verdünner verwendet wurden. Die Hydrogele wurden durch Messung des Wasserrückhaltevermögens, der Sauerstodiffusions- und permitionskoeffizienten, der mechanischen Eigenschaften und der Lichtdurchlässigkeit charakterisiert. Dabei zeigte sich, daß die Hydrogele bis zu 80 Gew.-% Wasser aufnehmen können, wobei mit steigendem Wassergtehalt deren mechanische Festigkeit drastisch sinkt. Der Ssuerstoffdiffusionskoeffizient der gequollenen Hydrogele beträgt 10-6 cm2s-1, der Sauerstoffpermeationskoeffizient 1013 cm2s-1Pa-1, und die Lichtdurchlässigkeit liegt im Bereich von 500 bis 700 nm bei über 90%.
    Notes: Hydrogels are synthesized from methyl methacrylate (MMA) and N-vinyl-2-pyrrolidone (NVP) with 1,1,1-trimethylol propane trimethacrylate (TPTA) as a crosslinking agent. It was polymerized under UV radiation (365nm) with a small amount of photosensitizer, diethoxy acetophenone (DEAP), acclerator and diluent, triethanol amine (TEA). The hydrogels were characterized by measuring the water retention, dissolved oxygen diffusivity and permeability, mechanical strength, and light transparency. The hydrogels can retain water up to 80 wt.-% and the mechanical strenght is weakened as the water content is increased in the gel. The dissolved oxygen diffusivity and permeability in the swelling hydrogels are determined to be 10-6 cm2/sec and 1013 cm2s-1 Pa-1, respectively. The light transparency is over 90% in the wave lenght ranging from 500 to 700 nm.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.051960104
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    New epoxy resins. I. The stability of epoxy-trialkoxyboroxines triaryloxyboroxine systemCorrected proofs received January 28, 1982 (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 1177-1190 
    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: A polymer with high aromaticity and/or cyclic ring structures chain backbone usually has high heat, thermal, and flame resistance. Two diglycidyl ethers of bisphenols were prepared from 4,4′ isopropylidenediphenol (DGEBA) and 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) for evaluation. Four boroxines - trimethoxyboroxine (TMB), triethoxyboroxine (TEB), triisopropoxyboroxine (TIPB) and triphenoxyboroxine (TPB) - were used as the curing agents. DGEBA and DGEBF cured with various boroxines indicate that the trend for their respective glass transition temperature (Tg's), degradation temperatures (Td's), and gel fractions are TMB-cured epoxy ≈ TEB-cured epoxy 〈 TIPB cured epoxy 〈 TPB cured epoxy. The DGEBF system usually has a higher Tg, Td, gel fraction, oxygen index (OI), and char yield than the related DGEBA system. DGEBF/DGEBA (80/20 mol ratio) shows a synergistic effect in regard to char formation. This effect exists not only in the copolymer system but also in blended homopolymers of the separately cured resins. A modified mechanism for the polymerization of phenyl glycidyl ether (PGE) with TMB has been proposed.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1982.070270407
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    The effects of aromatic solvents on the photopolymerization rates of isoprene, ethyl methacrylate, and styrene (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1539-1547 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photochemical polymerization rates of isoprene, ethyl methacrylate, and of styrene in various aromatic solvents were measured. The average lifetimes of propagating radicals were measured by the rotating sector method. The polymerization rate constants, Kp, were determined and compared with dipole moments (μ) and Hammett σ constants for the aromatic solvents. Linear correlations of log(kp/kp, benzene) vs. μ and σ were obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280620
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Yield and fracture mechanisms in ABS (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 503-521 
    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: The deformation and fracture characteristics of ABS have been investigated under tension, compression, and tension-compression fatigue cycling. The behavior of the rubber-modified polymer is compared with that of unmodified styrene-acrylonitrile, copolymer. The dispersed rubber particles in ABC cause extensive plastic deformation of the matrix material, markedly reduce the compressive yield stress, and, under tensile loading, cause yielding rather than early fracture. Under alternating stress conditions crazes occur sooner and lead to earlier craze breakdown, crack development, and reduced lifetime to fracture. The influence of rate of loading has been studied under applied tension and under fatigue cycling. The tensile yield stress varies linearly with the log of the strain rate in accord with the Eyring rate equation and, from the measured slope, the activation volume is estimated to be 2.2 nm3. The time to fatigue fracture reduces significantly with increasing frequency while cycles to fracture increase at a modest rate. Fatigue failure in ABS is not a cycle-dependent process, nor is it in accord with a damage accumulation model, but it more nearly resembles the former. The influence of a dispersed rubber phase, and of loading rate, on fracture surface morphology is discussed.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400317
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Polymerization of olefins through heterogeneous catalysis XI: Gas phase sequential polymerization kinetics (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 1573-1588 
    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: A unique series of ethylene and propylene sequential polymerization experiments have been carried out in a stirred bed gas phase reactor using unsupported Stauffer AA catalyst (TiCl3· \documentclass{article}\pagestyle{empty}\begin{document}$\frac{1}{3}$\end{document}AlCl3). Several interesting kinetic results were observed. It was found that propylene causes rate enhancement for a subsequent ethylene polymerization but that ethylene causes a rate reduction for a subsequent propylene polymerization. Furthermore, the rate enhancement/reduction effect increases with the duration of the preceding polymerization. Chemical/kinetic effects were found to be the likely causes of both the rate enhancements and the rate reductions observed during sequential polymerization. It was also shown that enhanced monomer sorption caused by the presence of a more soluble component, such as a heavier comonomer, does contribute to rate enhancement during simultaneous copolymerizations, but is not a factor for sequential polymerizations. © 1993 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070490908
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Polymerization of olefins through heterogeneous catalysis X: Modeling of particle growth and morphology (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 44 (1992), S. 1389-1414 
    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: The development of a detailed model describing particle growth in olefin copolymerization systems is presented. The Multigrain Model considers in detail monomer sorption, mass transfer, and changing porosity within the growing particle, as well as heat and mass transfer across the external film of the particle. The model predicts catalyst performance, including polymerization rates and particle morphology, in different reactor media without parameter adjustment. Internal void fractions are calculated through an examination of the relative growth rates within the growing particle. The model is used to examine the effects of mass transfer limitations, prepolymerization, and nonuniform metal distribution on the particle growth process. Model predictions of morphology show the same trends as observed experimentally.
    Additional Material: 23 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070440811
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    New epoxy resins. II. The preparation, characterization, and curing of epoxy resins and their copolymers (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 3289-3312 
    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: A polymer having high aromaticity and/or cyclic ring structures in the chain backbone usually gives high heat resistance and flame resistance. Five glycidyl ether-type epoxy resins are prepared from bisphenol A (DGEBA), 9,9-bis(4-hydroxyphenyl)fluorene (DGEBF), 3,6-dihydroxyspiro-[fluorene-9,9′-xanthane] (DGEFX), 10,10-bis(4-hydroxyphenyl) anthrone (DGEA), and 9,9,10,10-tetrakis(4-hydroxyphenyl)anthracene (TGETA) in order to study structure-thermal stability-flame resistance property relationships. In this study, trimethoxyboroxine (TMB) and diaminodiphenylsulfone (DDS) are employed as the curing agents. The char yield at 700°C under a nitrogen atmosphere and the glass transition temperature (Tg) for the uncured resins decrease according to the sequence TGETA 〉 DGEFX 〉 DGEA 〉 DGEBF 〉 DGEBA. The Tg values for these cured epoxy resins are DGEBA 〈 DGEBF 〈 DGEFX 〈 DGEA. A Tg for the TGETA is not obtainable but would be expected to be the highest. The char yields at 700°C of these cured epoxy resins have the same trend as the uncured resins. DGEBF, DGEFX, DGEA, and TGETA added to the DGEBA system show increases in the char yield, Tg, and oxygen index with increasing concentration of these novel epoxy resins.
    Additional Material: 25 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1982.070270909
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    New epoxy resins. III. Application of fourier transform IR to degradation and interaction studies of epoxy resins and their copolymers (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 28 (1983), S. 1077-1091 
    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: In the Fourier transform infrared (FT-IR) study, diglycidyl ether of bisphenol A (DGEBA) did not show aldehyde or perester absorption when it was normally cured with trimethoxyboroxine (TMB) under a nitrogen atmosphere. Neither alumina nor gold surfaces would cause oxidation of the system. In air, alumina appeared to accelerate the oxidation when compared to gold. The cure of the epoxy in oxygen appeared to cause increased Claisen rearrangement when compared with the same cure in a nitrogen atmosphere. The DGEBA cured with TMB under air or nitrogen atmospheres showed differences in their degradation patterns. The TMB-cured DGEBA and diglycidyl ether of 9,9-bis(4-hydroxyphenyl) fluorene (DGEBF) copolymer had a higher degree of reaction and lower degradation than was shown by the synthetically generated spectra based on the FT-IR summation of the spectra of the respective homopolymers.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1983.070280314
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...