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Fracture behaviour of controlled‐rheology ethylene–propylene block copolymers
Author(s) -
Salazar Alicia,
Martín Tamara,
Navarro José M,
Rodríguez Jesús
Publication year - 2011
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.3012
Subject(s) - materials science , melt flow index , crystallinity , composite material , rheology , ultimate tensile strength , fracture toughness , ductility (earth science) , elastomer , ethylene propylene rubber , copolymer , molar mass distribution , peroxide , ethylene , organic peroxide , elongation , polymer , chemistry , creep , catalysis , organic chemistry
The evolution of the molecular weight distribution and the thermal, mechanical and fracture behaviour of controlled‐rheology ethylene‐propylene block copolymers ( ca 8 wt% ethylene content) has been analysed. Various concentrations of di‐ tert ‐butylperoxide were utilized. The melt flow index increased with the peroxide content due to the reduction of the molecular weight and the narrowing of the molecular weight distribution. However, the thermal behaviour and degree of crystallinity were not improved and some mechanical properties, such as the tensile strength and elongation at break, presented an anomalous behaviour. This trend can be explained by the presence of the elastomeric phase. The addition of peroxide influenced strongly the J – R curves obtained via the elastic–plastic fracture mechanics approach. The slope of these curves was markedly reduced with addition of peroxide to almost being flat for the highest concentration. This loss of ductility and the sudden decrease of the fracture toughness values with an increasing amount of peroxide were mainly due to the reduction in the molecular weight. Copyright © 2011 Society of Chemical Industry