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  • 1
    Electronic Resource
    Electronic Resource
    On the cryogenic relaxation in polycarbonate (1981)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 19 (1981), S. 295-298 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1981.130190603
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanical relaxation in polycarbonate-polysulfone blends (1973)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 2715-2724 
    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: Lexan polycarbonate and polysulfone P-1700 were blended to various weight percentages by dissolution in methylene chloride. The blended material was reclaimed in the form of evaporated thin films which were dried, ground, and molded. Low-frequency mechanical relaxation tests were run on specimens machined from this material as a function of composition and thermal treatment. In addition to the β-peak, a second peak, β′, was resolved in unannealed 75 wt/o P-1700 specimens. These results are presented and a possible interpretation is discussed and compared with previously proposed mechanisms.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1973.070170908
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  • 3
    Electronic Resource
    Electronic Resource
    Thermally stimulated discharge current studies on low-temperature relaxations in polycarbonate (1976)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 20 (1976), S. 2879-2892 
    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 β-relaxation in polycarbonate has been investigated by the thermally stimulated discharge current (TSC) technique. The polarization of the β-peak in polycarbonate is shown to be uniform. Two broad peaks centered at 130° and 200°K were observed. Furthermore, two single relaxation processes were resolved for the lower temperature peak. The high temperature peak was also resolved into two peaks, however, only one of them was a single relaxation process. The individual peaks satisfied the dipolar theory, and the three peaks are associated with activation energies of 0.24, 0.27, and 0.47 eV, and temperatures of the peak maxima were 121°, 131°, and 193°K, respectively. The mechanism attributed to each peak is discussed and does not appear to contradict the results of conventional dielectric and mechanical relaxation and NMR measurements on the β-relaxation in polycarbonate.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1976.070201022
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  • 4
    Electronic Resource
    Electronic Resource
    Thermally stimulated depolarization current studies on strain-induced relaxations in polymers (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 2459-2469 
    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: Thermally stimulated depolarization current (TSD) method has been used to study the molecular relaxation from room temperature up to the glass-transition temperature for three plastically deformed polymers. A well-defined distinct α′ peak has been observed in the vicinity of 70°C for polycarbonate, polysulfone, as well as poly(ethylene terephthalate), that had been annealed above Tg and subsequently cold-rolled. Since this relaxation is not observed after the initial measurements, it is a nonequilibrium relaxation. In the case of polycarbonate, the nonreversible α′ process had an activation energy ranging from 1.22 to 1.75 eV and an intensity proportional to the degree of deformation resulting from cold-rolling. The spontaneous polarization in the rolled material was believed to originate from the initial anisotropy which was subsequently enhanced by the rolling process. Density measurements, as well as the birefringence observation, have been performed on the rolled specimens. All the studies led to the conclusion that the molecular motion responsible for this α′ peak was the disorientation of local chain segments from their aligned conformation frozen in during the cold-work.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260731
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  • 5
    Electronic Resource
    Electronic Resource
    Thermally stimulated discharge current studies on low-temperature relaxation in epoxy resin (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 25 (1980), S. 1355-1363 
    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: Thermally stimulated discharge current (TSDC) analysis has been used to characterize the low-temperature (100-300 K) molecular relaxation processes (β relaxation) of an epoxy resin. Experiments were performed on a resin system composed chiefly of tetraglycidyl-4,4′-diaminodiphenyl-methane and diaminodiphenyl sulfone (TGDDM/DDS). Polarization of the epoxy of the resin appears to be due to preferential orientations of dipoles in the temperature range studied. The broad β-dispersion peak exhibits considerable “structure,” and it promises to prove rich in information related to polarization and relaxation processes in the epoxy resins. It is seen that TSDC can reveal clearly the difference between the degree of curing for epoxy resins. Temperature dependence of a mean activation energy calculated from the discharging processes reveals several temperature ranges over which common molecular relaxation events are probably occurring.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1980.070250709
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  • 6
    Electronic Resource
    Electronic Resource
    Correlation between the mechanical behavior and relaxation processes in the plastically deformed polycarbonate (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 2471-2478 
    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 low-temperature β relaxation has been studied via thermally stimulated depolarization current (TSD) method for polycarbonate that had been cold-rolled and subsequently undergone the α′ relaxation at 70°C as a function of time. It has been found that the intensity of the β process increased as the annealing at 70°C increased. The analysis of the activation energy spectrum associated with the β relaxation indicated that the enhancement in the β intensity was due to the liberation of local dipoles from their aligned orientation as a result of undergoing the α′ relaxation process. Tensile flow curves have also been determined for the same set of specimens. Similar enhancement was also observed in the yield stress behavior. In view of the good correlation between the mechanical property and the structural change revealed by the relaxation study, it was concluded that the variation of the yield stress and the work-hardening in the rolled polymer was primarily associated with those parts of the chain that had been disoriented from their frozen-in conformations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260732
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  • 7
    Electronic Resource
    Electronic Resource
    Thermally stimulated discharge current studies on the effect of thermal treatment on the strength of polycarbonate (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 199-210 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is well known that polycarbonate annealed at 80-130°C undergoes gradual changes in mechanical properties. Annealing below Tg (ca. 150°C) results in a decrease in impact resistance and an increase in strength. Polycarbonate has three single relaxation processes and some distributed relaxation processes in the temperature range between 100 and 250°K (the β transition region). The effect of thermal pretreatment on the relaxation has been investigated by the thermally stimulated discharge current technique. Partial heating, peak cleaning, and theoretical fitting have also been performed and the activation parameters associated with the relaxation processes have also been calculated to assist in the analysis of the relationship between effects of annealing and structural motions in polycarbonate.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.180150201
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  • 8
    Electronic Resource
    Electronic Resource
    Studies of epoxy resin systems: Part A: A study of the origins of the secondary relaxations of epoxy resins by thermally stimulated depolarization (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1205-1212 
    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: The relaxation behavior of several epoxy resin systems, which have systematic structural differences, has been studied by the thermally stimulated discharge (TSD) technique. Two TSD peaks centered at about 115°K (β peak) and 185°K (β peak) were found for epoxy resins cured with a diamine. Structural change, either in the epoxy resin molecule or the amine molecule, did not seem to affect those two peaks. The TSD thermogram of the DGEBA (diglycidyl ether of disphenol A) epoxy resin part only showed a small new peak at 160°K instead of the ft peak at 185°K. This result, together with the fact that postcuring increased β peak height, leads to the conclusion that the ft peak is most likely due to the newly-created molecular segment during the curing reaction. The peak at 160°K was assigned to the epoxy group. This assignment was based on the fact that the 160°K peak of an epoxy homopolymer, which has fewer epoxy groups, was smaller than that of the parent DGEBA. The β and γ peaks were found to be of distributed characteristics, and the distribution of activation energy was studied by the partial heating method.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221806
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  • 9
    Electronic Resource
    Electronic Resource
    Studies of epoxy resin systems: Part B: Effect of crosslinking on the physical properties of an epoxy resin (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1213-1220 
    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: An epoxy system consisting of diglycidyl ether of butanediol, DGEB, cured with 4-4′ diaminodiphenyl sulfone, DDS, has been used for a study of the effect of crosslinking density on the properties of the epoxy resin. Because of the low curing rate at room temperature and the low glass-transition temperature, this system was amenable to a wide range of controlled cross-linking density. The crosslinking density was monitored by FTIR (Fourier transform infrared spectroscopy), which followed the change in concentration of the epoxy groups during the curing reaction. The bulk density was found to increase linearly with the crosslinking density. The modulus, the upper yield point, the lower yield point, and the degree of retraction of a deformed sample all increased with the degree of crosslinking. The thermally stimulated depolarization (TSD) β-peak was found to vary with crosslinking density, but the γ-peak was not changed. The TSD a peak was found to decrease in strength, but increased in temperature as the crosslinking density increased. This observation suggests that TSD measurements arc a good monitor of crosslinking density of epoxy resins, particularly near the final stage of the crosslinking reaction.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221807
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  • 10
    Electronic Resource
    Electronic Resource
    Studies of epoxy resin systems: Part D: Fracture toughness of an epoxy resin: A study of the effect of crosslinking and sub-Tg aging (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1228-1236 
    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: The fracture toughness of an epoxy resin system, diglycidyl ether of butanediol, DGEB, cured with 4-4′ diaminodiphenyl sulphone, DDS, has been studied by varying the crosslinking density and state of aging. A stable, but rough, crack propagation was observed with specimens that were 99 percent cured and quenched. When the extent of curing was less than 99 percent or the material was aged for more than 20 min at 62°C, crack propagation was of the unstable stick-slip nature. Aging was found to decrease the initiation fracture toughness dramatically, but the arrest fracture toughness was almost unchanged. This result was associated with a change of relaxation strength of the primary, a, transition with aging. An increase of crosslinking density was found initially to reduce the fracture toughness of this epoxy resin, but the fracture toughness increased after 87 percent of curing. The initial decrease of the fracture toughness was attributed to a decrease of relaxation strength of the primary transition (i.e., the area under the α-relaxation peak), while the increase of the fracture toughness after 87 percent curing was explained by the onset of the stablerough crack propagation, Micrographs taken by scanning electron microscopy-showed possible existence of blunting during crack propagation and a decrease of blunting with the extent of aging.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221809
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