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Fracture behaviour of polypropylene films at different temperatures: fractography and deformation mechanisms studied by SEM |
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| Affiliation: | a Departament Ciència dels Materials i Enginyeria Metal lúrgica, Centre Català del Plàstic, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona, Spain b School of Aerospace, Mechanical and Mechatronic Engineering, Centre for Advanced Materials Technology (CAMT), University of Sydney, Sydney, NSW 2006, Australia c MEEM, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong |
| Abstract: | The fracture surfaces and the deformation micro-mechanisms of one polypropylene homopolymer and three ethylene-propylene block copolymers (EPBC) have been studied by scanning electron microscopy. The results are compared to the essential work of fracture parameters obtained in a previous study with deeply double-edge-notched-tension samples of films fractured between −40 and 70 °C. The homopolymer shows shear-yielding at T≥−20 °C, but at lower T, crazing prevails. The EPBC display shear-yielding for T>0 °C, while a combination of cavitation and shear-yielding occurs at lower T, which is responsible for stress-whitening. The variations of the specific essential fracture work and specific plastic work with T and with ethylene content have been successfully explained in terms of the prevalent deformation mechanisms. |
| Keywords: | Polypropylene Essential fracture work Ethylene-propylene block copolymers |
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