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  • Chemistry  (4)
  • 1985-1989  (4)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Structure-property relationships in rubber-toughened epoxies (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1466-1476 
    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: Epoxies toughened with two reactive liquid rubbers, an epoxy-terminated butadiene acrylonitrile rubber (ETBN) and an amino-terminated butadiene acrylonitrile rubber (ATBN), were prepared and studied in terms of their structure property relationships. A two-phase structure was formed, consisting of spherical rubber particles dispersed in an epoxy matrix. A broad distribution of rubber particles was observed in all the materials with most of the particles ranging in size from 1 to 4 μm, but some particles exceeding 20 μm were also found. Impact strength, plane strain fracture toughness (KIC), and fracture energy (GIC) were increased, while Young's modulus and yield strength decreased slightly with increasing rubber content and volume fraction of the dispersed phase. Both GIC and KIC were found to increase with increasing apparent molecular weight between crosslinks and decreasing yield strength. The increased size of the plastic zone at the crack tip associated with decreasing yield strength could be the cause of the increased toughness. An ATBN-toughened system containing the greatest amount of epoxy sub-inclusion in the rubbery phase demonstrated the best fracture toughness in this series. In the present systems, rubber-enhanced shear deformation of the matrix is considered to be the major toughening mechanism. Curing conditions and the miscibility between the liquid rubber and the epoxy resin determine the phase morphology of the resulting two-phase systems. Kerner's equation successfully describes the modulus dependence on volume fraction for the two-phase epoxy materials.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760292008
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  • 2
    Electronic Resource
    Electronic Resource
    Fatigue crack propagation of rubber-toughened epoxiesThis paper is dedicated to the Memory of Dr. Jhon A. Manson, A Pioneer in the Field of Polymer Science and Engineering. (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 1477-1487 
    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: Epoxies containing epoxy-terminated butadiene acrylonitrile rubber (ETBN) or amino-terminated butadiene acrylonitrile rubber (ATBN) were prepared and studied in terms of fatigue crack propagation (FCP) resistance and toughening mechanisms. Rubber incorporation improves both impact and FCP resistance, but results in slightly lower Young's modulus and Tg As Tg increases, the degree of toughening decreases. Rubber-induced shear yielding of the epoxy matrix is believed to be the dominant toughening mechanism. Decreasing fatigue resistance with increasing cyclic frequency is observed for both neat and rubber-toughened epoxies. This result may be explained by the inability of these materials to undergo possible beneficial effects of hysteretic heating. FCP resistance is linearly proportional to Mc1/2, where Mc is the apparent molecular weight between crosslinks determined on the rubber-toughened material. FCP resistance also increases with increasing static fracture toughness KIC. ATBN-toughened epoxies demonstrated better fatigue resistance than ETBN-toughened systems.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760292009
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  • 3
    Electronic Resource
    Electronic Resource
    Interplay of rubber network theory with the damping behavior of crosslinked polyurethanes (1989)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 27 (1989), S. 2251-2268 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Network formation (branching) theory was used to examine the relationships between network structure and concomitant sound and vibration damping. For a series of model polyether-based polyurethane networks with varying stoichiometry and composition, the glass transition temperature Tg, was found to increase with increasing concentration of elastically active network chains, EANCs, as well as the ratio of branch OH group concentration to the total OH group concentration ρ. The values of (tan δ)max, the peak height of tan δ at Tg, linearly decrease with increasing concentration of EANCs, regardless of the ρ values. However, the loss area (LA), equal to the integral of the linear loss modulus-temperature curve, is independent of the concentration of EANCs and/or ρ. Utilizing group contribution analysis techniques, the value of the main chain -O- group contribution, LA-O-, is 19.1 GPa·K/g, a rather large value. This finding gives insight into why polyether urethanes are preferred for many damping applications.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1989.090271108
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  • 4
    Electronic Resource
    Electronic Resource
    Phase continuity and inversion in polymer blends and simultaneous interpenetrating networks (1986)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 517-524 
    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: A semi-empirical expression for predicting phase continuity and inversion in polymer blends and simultaneous interpenetrating networks (SINs) was developed and examined experimentally. A rheological model based on the volume fraction, φ, and viscosity, η, led to the equation \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{{\rm \eta }_{\rm 1} }}{{{\rm \eta }_{\rm 2} }} \cdot \frac{{\phi _{\rm 2} }}{{\phi _{\rm 1} }} \cong 1 $$\end{document} as the criteria for dual phase continuity for phases 1 and 2. This relation was evaluated for two systems: a castor oil polyester-urethane/polystyrene SIN, and a mechanical blend of polystyrene and polybutadiene. Literature data was also examined. A gradual phase inversion was found, with a region of dual phase continuity in between. While predictions of phase continuity were confirmed for the mechanical blends, they were not confirmed for the SIN system. This was probably due to rapid gelation at the point of phase inversion.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760260802
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