Micron and nanostructured rubber toughened epoxy: A direct comparison of mechanical, thermomechanical and fracture properties

Nicholas T. Kamar, Lawrence T. Drzal

    Research output: Contribution to journalArticle

    • 3 Citations

    Abstract

    Phase separating rubbers are a well-documented toughening additive to epoxies. However, their effectiveness begins to plateau as the loading approaches 10 phr. To better understand this phenomenon, we directly compared the mechanical, thermomechanical, fracture properties and toughening mechanisms of the diglycidyl ether of bisphenol-A (DGEBA)/m-phenylenediamine (mPDA) system (Tg = 154 °C) toughened with carboxyl-terminated butadiene-acrylonitrile (CTBN) and the triblock copolymer poly(styrene)-block-poly(butadiene)-block-poly(methylmethacrylate) (SBM), respectively. The SBM formed a nanostructured thermoset and thus was a more efficient toughening agent than CTBN, which forms micron scale, rubbery inclusions in the epoxy. At 10 phr SBM, the fracture toughness (MPa∗m1/2) was increased by 220%, while the 10 phr CTBN modified epoxy containing 18 and 26% acrylonitrile showed 60 and 80% increases, respectively. Unlike the CTBN modified epoxy, SBM increased the fracture toughness with increasing concentration. Fracture surface analysis of the SBM modified epoxy via scanning electron microscopy identified the toughening mechanism as cavitation of ∼100 nm spherical micelles, void growth of the epoxy and concomitant matrix shear yielding. While both the CTBN and SBM modified epoxy exhibit similar toughening mechanisms, the nanoscopic SBM particles had an interparticle distance one order of magnitude smaller than that of the CTBN modified epoxy. Thus, a finer dispersion of nanoscopic, spherical micelles resulted in massive plastic deformation of the epoxy upon activation of cavitation, void growth and matrix shear yielding toughening mechanisms. Finally, dynamic mechanical analysis indicated that SBM did not decrease epoxy Tg, while the Tg of CTBN modified epoxy decreased with both increasing concentration and acrylonitrile content.

    Original languageEnglish (US)
    Pages (from-to)114-124
    Number of pages11
    JournalPolymer (United Kingdom)
    Volume92
    DOIs
    StatePublished - Jun 1 2016

    Profile

    Butadiene
    Toughening
    Cimetidine
    Cavitation
    Micelles
    Fracture toughness
    Rubber
    Enzyme Reactivators
    Erythrasma
    Immunoglobulin A
    Thermosets
    Surface analysis
    Dynamic mechanical analysis
    Block copolymers
    Styrene
    Ethers
    Plastic deformation
    Chemical activation
    Scanning electron microscopy
    Inborn Errors Amino Acid Metabolism

    Keywords

    • Block copolymers
    • Fracture toughness
    • Nanocomposites

    ASJC Scopus subject areas

    • Organic Chemistry
    • Polymers and Plastics

    Cite this

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    title = "Micron and nanostructured rubber toughened epoxy: A direct comparison of mechanical, thermomechanical and fracture properties",
    abstract = "Phase separating rubbers are a well-documented toughening additive to epoxies. However, their effectiveness begins to plateau as the loading approaches 10 phr. To better understand this phenomenon, we directly compared the mechanical, thermomechanical, fracture properties and toughening mechanisms of the diglycidyl ether of bisphenol-A (DGEBA)/m-phenylenediamine (mPDA) system (Tg = 154 °C) toughened with carboxyl-terminated butadiene-acrylonitrile (CTBN) and the triblock copolymer poly(styrene)-block-poly(butadiene)-block-poly(methylmethacrylate) (SBM), respectively. The SBM formed a nanostructured thermoset and thus was a more efficient toughening agent than CTBN, which forms micron scale, rubbery inclusions in the epoxy. At 10 phr SBM, the fracture toughness (MPa∗m1/2) was increased by 220%, while the 10 phr CTBN modified epoxy containing 18 and 26% acrylonitrile showed 60 and 80% increases, respectively. Unlike the CTBN modified epoxy, SBM increased the fracture toughness with increasing concentration. Fracture surface analysis of the SBM modified epoxy via scanning electron microscopy identified the toughening mechanism as cavitation of ∼100 nm spherical micelles, void growth of the epoxy and concomitant matrix shear yielding. While both the CTBN and SBM modified epoxy exhibit similar toughening mechanisms, the nanoscopic SBM particles had an interparticle distance one order of magnitude smaller than that of the CTBN modified epoxy. Thus, a finer dispersion of nanoscopic, spherical micelles resulted in massive plastic deformation of the epoxy upon activation of cavitation, void growth and matrix shear yielding toughening mechanisms. Finally, dynamic mechanical analysis indicated that SBM did not decrease epoxy Tg, while the Tg of CTBN modified epoxy decreased with both increasing concentration and acrylonitrile content.",
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    author = "Kamar, {Nicholas T.} and Drzal, {Lawrence T.}",
    year = "2016",
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    doi = "10.1016/j.polymer.2016.03.084",
    volume = "92",
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    T1 - Micron and nanostructured rubber toughened epoxy

    T2 - Polymer (United Kingdom)

    AU - Kamar,Nicholas T.

    AU - Drzal,Lawrence T.

    PY - 2016/6/1

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    N2 - Phase separating rubbers are a well-documented toughening additive to epoxies. However, their effectiveness begins to plateau as the loading approaches 10 phr. To better understand this phenomenon, we directly compared the mechanical, thermomechanical, fracture properties and toughening mechanisms of the diglycidyl ether of bisphenol-A (DGEBA)/m-phenylenediamine (mPDA) system (Tg = 154 °C) toughened with carboxyl-terminated butadiene-acrylonitrile (CTBN) and the triblock copolymer poly(styrene)-block-poly(butadiene)-block-poly(methylmethacrylate) (SBM), respectively. The SBM formed a nanostructured thermoset and thus was a more efficient toughening agent than CTBN, which forms micron scale, rubbery inclusions in the epoxy. At 10 phr SBM, the fracture toughness (MPa∗m1/2) was increased by 220%, while the 10 phr CTBN modified epoxy containing 18 and 26% acrylonitrile showed 60 and 80% increases, respectively. Unlike the CTBN modified epoxy, SBM increased the fracture toughness with increasing concentration. Fracture surface analysis of the SBM modified epoxy via scanning electron microscopy identified the toughening mechanism as cavitation of ∼100 nm spherical micelles, void growth of the epoxy and concomitant matrix shear yielding. While both the CTBN and SBM modified epoxy exhibit similar toughening mechanisms, the nanoscopic SBM particles had an interparticle distance one order of magnitude smaller than that of the CTBN modified epoxy. Thus, a finer dispersion of nanoscopic, spherical micelles resulted in massive plastic deformation of the epoxy upon activation of cavitation, void growth and matrix shear yielding toughening mechanisms. Finally, dynamic mechanical analysis indicated that SBM did not decrease epoxy Tg, while the Tg of CTBN modified epoxy decreased with both increasing concentration and acrylonitrile content.

    AB - Phase separating rubbers are a well-documented toughening additive to epoxies. However, their effectiveness begins to plateau as the loading approaches 10 phr. To better understand this phenomenon, we directly compared the mechanical, thermomechanical, fracture properties and toughening mechanisms of the diglycidyl ether of bisphenol-A (DGEBA)/m-phenylenediamine (mPDA) system (Tg = 154 °C) toughened with carboxyl-terminated butadiene-acrylonitrile (CTBN) and the triblock copolymer poly(styrene)-block-poly(butadiene)-block-poly(methylmethacrylate) (SBM), respectively. The SBM formed a nanostructured thermoset and thus was a more efficient toughening agent than CTBN, which forms micron scale, rubbery inclusions in the epoxy. At 10 phr SBM, the fracture toughness (MPa∗m1/2) was increased by 220%, while the 10 phr CTBN modified epoxy containing 18 and 26% acrylonitrile showed 60 and 80% increases, respectively. Unlike the CTBN modified epoxy, SBM increased the fracture toughness with increasing concentration. Fracture surface analysis of the SBM modified epoxy via scanning electron microscopy identified the toughening mechanism as cavitation of ∼100 nm spherical micelles, void growth of the epoxy and concomitant matrix shear yielding. While both the CTBN and SBM modified epoxy exhibit similar toughening mechanisms, the nanoscopic SBM particles had an interparticle distance one order of magnitude smaller than that of the CTBN modified epoxy. Thus, a finer dispersion of nanoscopic, spherical micelles resulted in massive plastic deformation of the epoxy upon activation of cavitation, void growth and matrix shear yielding toughening mechanisms. Finally, dynamic mechanical analysis indicated that SBM did not decrease epoxy Tg, while the Tg of CTBN modified epoxy decreased with both increasing concentration and acrylonitrile content.

    KW - Block copolymers

    KW - Fracture toughness

    KW - Nanocomposites

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