Investigation of Toughening Micro-Mechanisms in Polypropylene/Ethylene-Propylene-Diene Rubber Blends at Crack and Notch Tips

    (Received 1 October 2013; accepted 30 December 2013)

    Published Online: 2014

    CODEN: MPCOAD

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    Abstract

    Polypropylene (PP) has the highest growth rate among commodity thermoplastics and is widely used in many applications including packaging, auto, and pipe industries. The relatively low impact strength of this polymer has led to the production of rubber-modified polypropylene with higher impact strength. To promote the applications of these blends, it is necessary to establish the relationship between the mechanical performance and fracture micro-mechanism(s). Fracture behavior is different depending on the application where either crack or notch might be present. In this study, a systematic approach is taken with the aim of understanding the toughening micro-mechanisms of polypropylene/ethylene-propylene-diene monomer (PP/EPDM) blends at both crack and notch tip using different microscopy techniques. Rubber-modified blends were prepared using a twin screw extruder. The samples were exposed to different mechanical, physical, and microscopic examinations. X-ray diffractometer (XRD) and differential scanning calorimetry (DSC) techniques were used to study the crystalline structure. Impact and fracture toughness (JIC) tests were conducted to evaluate toughness of blends. Morphology and fracture behavior of the blends were investigated via transmission optical microscopy (TOM) and scanning electron microscopy (SEM). Results indicate that both impact strength and fracture toughness (JIC) increase with increasing EPDM content. The two parameters, however, do not follow the same trend. The microscopic evaluations reveal that massive crazing coupled with particle cavitation is the dominant toughening mechanism in PP/EPDM blends under quasi-static and impact loading. Morphological features of the damage zone are different in these two loading conditions.


    Author Information:

    Farhang, L.
    Polymeric Materials Research Group, Dept. of Materials and Science Engineering, Sharif Univ. of Technology, Tehran,

    Bagheri, R.
    Polymeric Materials Research Group, Dept. of Materials and Science Engineering, Sharif Univ. of Technology, Tehran,


    Stock #: MPC20130062

    ISSN: 2165-3992

    DOI: 10.1520/MPC20130062

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    Author
    Title Investigation of Toughening Micro-Mechanisms in Polypropylene/Ethylene-Propylene-Diene Rubber Blends at Crack and Notch Tips
    Symposium , 0000-00-00
    Committee E08