Local process-dependent structural and mechanical properties of extrusion blow molded high-density polyethylene hollow parts. (February 2020)

• Record Type: Journal Article
• Authors: Ramakers-van Dorp, Esther; Eger, Benedikt; Raschen, Clemens; Urbanek, Michal; Möginger, Bernhard; Hausnerova, Berenika
• Is Part Of: Polymer testing. Volume 82(2020)
• Publication Date: 2020-02
• Subjects: Extrusion blow molding -- Local process-dependent properties -- Crystallinity -- Complex modulus -- Biaxiality; Polymers -- Testing -- Periodicals; Polymères -- Tests -- Périodiques; 620.1920287
• DOI: 10.1016/j.polymertesting.2019.106314
• Languages: English
• ISSNs: 0142-9418

Abstract

Abstract: Although applied for several decades, production of hollow plastic parts by extrusion blow molding (EBM) is still over-dimensioned. To overcome this issue, a thorough investigation of the process-structure-property relationship is required. In this study, the local process-structure-property relationship for high-density polyethylene EBM containers is analyzed with differential scanning calorimetry and dynamic mechanic analysis microindentation. Local process-dependent crystallinity and complex modulus data at various processing conditions are supplemented with wide-angle X-ray diffraction and transmission electron microscopy (TEM). The crystallinities and the complex moduli clearly show lower values close to the mold side than at the inner side and the middle of the cross-section, which reflects the temperature gradient during processing. Additionally, the orientation of the polymer chain (c-axis) reveals a low level of biaxiality with a slight tendency towards transverse direction. The biaxiality increases for low mold temperature and high draw ratio. Finally, biaxiality is confirmed with TEM, which reveals no preferred lamellar orientation. Highlights: Extrusion blow molded (EBM) process-dependent properties studied. Cross-sectional temperature distribution of EBM parts reflected in local properties. Crystallinity and complex moduli lower close to the mold wall. Biaxiality slightly enhanced by lower mold temperature and higher draw ratio.