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  • Articles  (31)
  • 2010-2014  (4)
  • 1975-1979  (27)
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  • Articles  (31)
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  • 1
    Electronic Resource
    Electronic Resource
    Isomeric Graft Copolymers and Interpenetrating Polymer Networks. Theory and Experiment (1976)
    s.l. : American Chemical Society
    Macromolecules 9 (1976), S. 743-749 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma60053a011
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  • 2
    Electronic Resource
    Electronic Resource
    Simultaneous Interpenetrating Networks Based on Castor Oil Elastomers and Polystyrene. 2. Synthesis and Systems Characteristics (1979)
    s.l. : American Chemical Society
    Macromolecules 12 (1979), S. 360-369 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma60069a002
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  • 3
    Electronic Resource
    Electronic Resource
    Fatigue crack propagation in crystalline polymers: effect of moisture in nylon 66 (1979)
    Springer
    Journal of materials science 14 (1979), S. 2482-2492 
    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 As part of a study of the effects of crystallinity on fatigue crack propagation (FCP) behaviour in crystalline polymers, the FCP response of nylon 66 was examined as a function of both stress intensity factor range (ΔK) and water content. It was found that FCP rates were exponential functions of ΔK, as expected. However, the FCP rates at constant ΔK decreased as the water content was increased to about 3%; at saturation (8% water), the FCP rates were higher than that observed in dry specimens. Results were interpreted in terms of the incorporation of tightly bound water up to a maximum of one water molecule per two amide groups (at∼ 2% water), followed by the incorporation of loosely bound water (at saturation). The tightly bound water evidently toughens the polymer, while the loosely bound water has a predominantly weakening effect. Examination of fracture surfaces revealed a transition from terminal unstable crack growth (at water contents up to 3%) to tearing (at saturation). Classical fatigue striations were observed only in the specimens containing 2% water—the first time such striations have been unequivocally identified for any crystalline polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00737039
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  • 4
    Electronic Resource
    Electronic Resource
    Fatigue crack propagation in polyacetal (1978)
    Springer
    Journal of materials science 13 (1978), S. 1038-1044 
    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 fatigue crack propagation characteristics of a typical commercial homopolymer and copolymer polyacetal were determined. These materials were found to be the most fatigue resistant plastics examined to date, thus confirming the generally high fatigue resistance of all crystalline polymers. A discontinuous fatigue cracking process was identified at all test frequencies in the acetal copolymer and at high frequencies in the homopolymer, while continuous crack propagation occurred at low test frequencies in the homopolymer. The discrete advance increments of the crack in the discontinuous mode were equal to the dimension of the prevailing crack-tip plastic zone. On a more local scale, the crack path is seen to be mainly trans-spherulitic in nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544699
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  • 5
    Electronic Resource
    Electronic Resource
    Castor-oil-based interpenetrating polymer networks: Synthesis and characterization (1977)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 21 (1977), S. 1531-1541 
    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: Castor oil was polymerized and crosslinked with sulfur or diisocyanates to form the vulcanized and urethane derivatives, respectively. Both types were swollen with a plastic-forming monomer plus crosslinker, and a second polymerization was carried out in situ. Polyblends were also made by emulsion polymerization of styrene and methyl methacrylate employing hydrolyzed castor oil as the soap. In all three polymerizations, a wide range of compositions was obtained. The resulting interpenetrating polymer networks were characterized using electron microscopy, modulus-temperature measurements, and stress-strain analysis. The polystyrene phase size of the castor oil-urethane/polystyrene IPN was shown to decrease with increased crosslinking of the castor oil component and with increased polystyrene contents. The modulus-temperature study showed two distinct glass transitions in all cases, with evidence of significant mixing of the two components in many cases. The stress-strain results show that some of the IPN's behave as reinforced, highly extensible elastomers at low polystyrene levels, and a rubber-toughened plastics at high levels of polystyrene or crosslinking.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1977.070210609
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  • 6
    Electronic Resource
    Electronic Resource
    Fatigue fracture processes in polystyrene (1976)
    Springer
    Journal of materials science 11 (1976), S. 479-490 
    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 Fatigue crack growth characteristics in polystyrene were studied as a function of stress intensity factor range and cyclic frequency. Precracked single edge notched and compact-tension type specimens made from commercially available polystyrene sheet (mol.wt. =2.7×105) were cycled under constant load at frequencies of 0.1, 1, 10 and 100 Hz, producing growth rates ranging from 4×10−7 to 4×10−3 cm/cycle. For a given stress intensity level, fatigue crack growth rates were found to decrease with increasing frequency, the effect being strongest at high stress intensity values. The variable frequency sensitivity of this polymer over the test range studied was explained in terms of a variable creep component. The macroscopic appearance of the fracture surface showed two distinct regions. At low stress intensity values, a highly reflective, mirror-like surface was observed which transformed to a rougher, cloudy surface structure with increasing stress intensity level. Raising the test frequency shifted the transition between these areas to higher values of stress intensity. The microscopic appearance of the mirror region revealed evidence of crack propagation through a single craze while the appearance of the rough region indicated crack growth through many crazes, all nominally normal to the applied stress axis. Electron fractographic examination of the mirror region revealed many parallel bands perpendicular to the direction of crack growth, each formed by a discontinuous crack growth process as a result of many fatigue cycles. The size of these bands was found to be consistent with the dimension of the crack tip plastic zone as computed by the Dugdale model. At high stress intensity levels a new set of parallel markings was found in the cloudy region which corresponded to the incremental crack extension for an individual loading cycle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540929
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  • 7
    Electronic Resource
    Electronic Resource
    On the generality of discontinuous fatigue crack growth in glassy polymers (1977)
    Springer
    Journal of materials science 12 (1977), S. 531-542 
    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 Fatigue fracture surface characteristics of five commercially available amorphous polymers [poly(methylmethacrylate) (PMMA), polycarbonate (PC), poly(vinyl chloride) (PVC), polystyrene (PS), and polysulphone (PSF)] as well as bulk-polymerized PMMA prepared over a wide range of molecular weights were studied to determine if common mechanisms of fatigue crack propagation prevail among these glassy polymers. In those polymers with viscosity-average molecular weight ¯M v≲2×105, the macroscopic appearance of the fracture surface showed the presence of a highly reflective mirror-like region which formed at low values of stress intensity and high cyclic test frequencies (∼100 Hz). The microscopic appearance of this region revealed that many parallel bands exist oriented perpendicular to the direction of crack growth and that the bands increase in size with ΔK. In all instances, the crack front advanced discontinuously in increments equal to the band width after remaining stationary for hundreds of fatigue cycles. Electron fractographic studies verified the discontinuous nature of crack extension through a craze which developed continuously with the load fluctuations. By equating the band size to the Dugdale plastic zone dimension ahead of the crack, a relatively constant yield strength was inferred which agreed well with reported craze stress values for each material. At higher stress intensity levels in all polymers and all values of ¯M v, another series of parallel bands were observed. These were also oriented perpendicular to the direction of crack growth and likewise increased in size with the range in stress intensity factor, ΔK. Each band corresponded to the incremental advance of the crack during one load cycle, indicating these markings to be classical fatigue striations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540278
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  • 8
    Electronic Resource
    Electronic Resource
    Frequency sensitivity of fatigue processes in polymeric solids (1975)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 252-260 
    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: One is faced with an interesting challenge when trying to explain the effect of test frequency on polymer fatigue performance. While hysteretic heating arguments appear sufficient to explain a diminution of fatigue resistance with increasing cyclic frequency in unnotched test samples, the enhancement of fatigue resistance in many polymers with increasing cyclic frequency in notched samples is still not clearly understood. In large measure, this is due to contradictory trends in fre-quency-sensitive material properties which affect the fatigue process. In this paper, a number of proposed fatigue models dealing with the time and strain rate dependence of elastic modulus, yield strength, creep and localized crack tip heating are examined and confronted with available data from the literature. Additional fatigue crack propagation data for poly(methyl methacrylate), poly (vinyl chloride), polystyrene, poly-carbonate, nylon 66, poly(vinylidene fluoride) and poly(2,6-dimethylphenylene oxide) were obtained and are reported herein. These data were obtained over a maximum frequency range of 0.1 to 100 Hz and, for selected polymers, with various waveforms. Frequency sensitivity is shown to be greatest in those polymers that show a high tendency for crazing. Relative fatigue behavior is found to reflect a competition between strain rate and creep effects. Where creep effects dominate, the total crack growth rate may be viewed as consisting of the summation of pure fatigue and creep components, respectively. Finally, the β transition appears to have a role, with frequency sensitivity being at a maximum for polymers where the β transition at room temperature occurs in the range of the experimental test frequency.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760150404
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  • 9
    Electronic Resource
    Electronic Resource
    Simultaneous interpetrating network based on castor oil elastomers and polystyrene. III. Morphology and glass transition behavior (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 869-877 
    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: Electron microscopy and dynamic mechanical spectroscopy (DMS) techniques were used to study the morphology and glass transition behavior of simultaneous interpenetrating networks (SIN's), based on three different castor oil derived elastomers, and polystyrene (PS) plastic erosslinked with 1 percent divinyl benzene. The castor oil elastomers consisted of either the sebacic acid polyester, 2,4-tolylene diisocyanate polyurethane, or the mixed poly(ester-urethane). Emphasis was placed on two compositions having 10 and 40 percent elastomer contents by weight of each type, the remainder being PS. In all cases, a two-phase morphology emerged. With the 10 percent elastomer composition, the use of vigorous stirring during the early stages of reaction resulted in materials having the crosslinked polystyrene as the continuous phase and elastomer domains (ranging from 100 to 8000 nm in size) as the discontinuous phase. The elastomer domains contained a polystyrene cellular structure, with the polystyrene cell sizes ranging from 50 to 300 nm size. Several examples showed morphologies resembling high impact polystyrene. Materials having a 40 percent elastomer content always showed a continuous phase of castor oil elastomer, with the PS displaying a bimodal size cellular structure. Domain sizes ranged from 10 to 860 nm. The DMS studies showed two well-defined glass transitions near their respective homopolymer glass transitions, but shifted inwards to greater or lesser extents indicating some molecular mixing between the two polymers. The glass transition of the pure elastomer phase occurred at -66°C for the castor oil polyester elastomer, -4°C for the castor oil polyurethane elastomer and -50°C for the castor oil poly(ester-urethane) elastomer. Phase separation in these materials is postulated to occur by two mechanisms: (1) multiple precipitation of polystyrene chains at progressive levels of polymerization and (2) microsyneresis processes. The thermodynamics of mixing and phase separation in polymerizing SIN's is examined in some detail.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760191210
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  • 10
    Electronic Resource
    Electronic Resource
    Castor oil based interpenetrating polymer networks, IV. Mechanical behavior (1977)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 17 (1977), S. 251-256 
    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 physical and mechanical properties of interpenetrating polymer networks (IPN's) based on castor oil-urethane and polystyrene are detailed in this paper. Dynamic mechanical spectroscopy showed extensive but incomplete molecular mixing of the two polymers. The glass transition temperatures of the IPN's gradually merged from two distinct transitions into one broad transition at an intermediate temperature as the crosslink level of the castor oil component was increased. At low polystyrene contents, the IPN's yielded stress-strain behavior similar to reinforced elastomers, but at high polystyrene contents, they exhibited increased elongation. For example, the latter materials showed well developed yield points. Stress whitening and necking were also observed, suggesting a possible failure mechanism by crazing. Cold drawing was exhibited by the materials under tension. The tensile strength and Young's modules were enhanced as the polymer II (polystyrene) content was increased at constant crosslink level of polymer I (castor oil-urethane). A similar effect was also observed by maintaining the polystyrene content constant but increasing the crosslink level of polymer I. The impact strength of the materials ranged from 32.1 to 53.4 N · m/m, which is approximately two to three times that of homopolymer polystyrene. The best materials were those with compositions in the range of 40-46 percent castor oil-urethane. The materials prepared by using tolylene diisocyanate as crosslinker for the castor oil phase had the best impact properties, especially at an NCO/OH ratio of 0.95.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760170408
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