Relationship between the structure and mechanical properties of polypropylene: Effects of the molecular weight and shear-induced structure

Claudia Stern, Achim Frick, G. Weickert

    Research output: Contribution to journalArticleAcademic

    39 Citations (Scopus)

    Abstract

    A series of homopolymer polypropylenes (PPs), within a weight-average molecular weight (Mw) range of 100-1600 kg/mol, were manufactured as dumbbell microspecimens. The effects of the molecular weight and shear-induced crystallization on the mechanical properties and morphology were studied to gain a better understanding of the structure-property relationship. The results showed that the crystallinity decreased from 50 to 41% and the lamellar thickness increased as Mw increased. Tensile tests demonstrated that the stiffness and especially the tensile strength rose to extremely high values (Young's modulus = 2400 N/mm2, stress at 30% strain = 120 N/mm2). Furthermore, the strain hardening effect was strongly affected by the lamellar thickness and highly oriented superstructures. Dynamic mechanical analysis demonstrated that the mobility of the molecular chains depended on Mw and on the lamellar thickness. In addition, the viscoelastic properties of unannealed and annealed samples indicated further the existence of shish-kebab structures caused by shear-induced crystallization during injection molding.
    Original languageUndefined
    Pages (from-to)519-533
    JournalJournal of applied polymer science
    Volume103
    Issue number1
    DOIs
    Publication statusPublished - 2007

    Keywords

    • poly(propylene) (PP)
    • Mechanical properties
    • shear
    • IR-72211
    • solid-state structure
    • structure-property relations

    Cite this

    @article{d7f98867890045d99e2f328ca5805b13,
    title = "Relationship between the structure and mechanical properties of polypropylene: Effects of the molecular weight and shear-induced structure",
    abstract = "A series of homopolymer polypropylenes (PPs), within a weight-average molecular weight (Mw) range of 100-1600 kg/mol, were manufactured as dumbbell microspecimens. The effects of the molecular weight and shear-induced crystallization on the mechanical properties and morphology were studied to gain a better understanding of the structure-property relationship. The results showed that the crystallinity decreased from 50 to 41{\%} and the lamellar thickness increased as Mw increased. Tensile tests demonstrated that the stiffness and especially the tensile strength rose to extremely high values (Young's modulus = 2400 N/mm2, stress at 30{\%} strain = 120 N/mm2). Furthermore, the strain hardening effect was strongly affected by the lamellar thickness and highly oriented superstructures. Dynamic mechanical analysis demonstrated that the mobility of the molecular chains depended on Mw and on the lamellar thickness. In addition, the viscoelastic properties of unannealed and annealed samples indicated further the existence of shish-kebab structures caused by shear-induced crystallization during injection molding.",
    keywords = "poly(propylene) (PP), Mechanical properties, shear, IR-72211, solid-state structure, structure-property relations",
    author = "Claudia Stern and Achim Frick and G. Weickert",
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    language = "Undefined",
    volume = "103",
    pages = "519--533",
    journal = "Journal of applied polymer science",
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    Relationship between the structure and mechanical properties of polypropylene: Effects of the molecular weight and shear-induced structure. / Stern, Claudia; Frick, Achim; Weickert, G.

    In: Journal of applied polymer science, Vol. 103, No. 1, 2007, p. 519-533.

    Research output: Contribution to journalArticleAcademic

    TY - JOUR

    T1 - Relationship between the structure and mechanical properties of polypropylene: Effects of the molecular weight and shear-induced structure

    AU - Stern, Claudia

    AU - Frick, Achim

    AU - Weickert, G.

    PY - 2007

    Y1 - 2007

    N2 - A series of homopolymer polypropylenes (PPs), within a weight-average molecular weight (Mw) range of 100-1600 kg/mol, were manufactured as dumbbell microspecimens. The effects of the molecular weight and shear-induced crystallization on the mechanical properties and morphology were studied to gain a better understanding of the structure-property relationship. The results showed that the crystallinity decreased from 50 to 41% and the lamellar thickness increased as Mw increased. Tensile tests demonstrated that the stiffness and especially the tensile strength rose to extremely high values (Young's modulus = 2400 N/mm2, stress at 30% strain = 120 N/mm2). Furthermore, the strain hardening effect was strongly affected by the lamellar thickness and highly oriented superstructures. Dynamic mechanical analysis demonstrated that the mobility of the molecular chains depended on Mw and on the lamellar thickness. In addition, the viscoelastic properties of unannealed and annealed samples indicated further the existence of shish-kebab structures caused by shear-induced crystallization during injection molding.

    AB - A series of homopolymer polypropylenes (PPs), within a weight-average molecular weight (Mw) range of 100-1600 kg/mol, were manufactured as dumbbell microspecimens. The effects of the molecular weight and shear-induced crystallization on the mechanical properties and morphology were studied to gain a better understanding of the structure-property relationship. The results showed that the crystallinity decreased from 50 to 41% and the lamellar thickness increased as Mw increased. Tensile tests demonstrated that the stiffness and especially the tensile strength rose to extremely high values (Young's modulus = 2400 N/mm2, stress at 30% strain = 120 N/mm2). Furthermore, the strain hardening effect was strongly affected by the lamellar thickness and highly oriented superstructures. Dynamic mechanical analysis demonstrated that the mobility of the molecular chains depended on Mw and on the lamellar thickness. In addition, the viscoelastic properties of unannealed and annealed samples indicated further the existence of shish-kebab structures caused by shear-induced crystallization during injection molding.

    KW - poly(propylene) (PP)

    KW - Mechanical properties

    KW - shear

    KW - IR-72211

    KW - solid-state structure

    KW - structure-property relations

    U2 - 10.1002/app.24156

    DO - 10.1002/app.24156

    M3 - Article

    VL - 103

    SP - 519

    EP - 533

    JO - Journal of applied polymer science

    JF - Journal of applied polymer science

    SN - 0021-8995

    IS - 1

    ER -