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Correlation between the fracture toughness and β‐crystal fraction in a β‐nucleated propylene‐based propylene–ethylene random copolymer
Author(s) -
Zhang Chunbo,
Liu Guoming,
Jiang Qianhong,
Zhao Ying,
Wang Dujin
Publication year - 2016
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.42930
Subject(s) - materials science , izod impact strength test , copolymer , composite material , ethylene propylene rubber , toughness , fracture toughness , brittleness , ethylene , toughening , polymer , ultimate tensile strength , catalysis , chemistry , organic chemistry
Propylene‐based propylene–ethylene random copolymer (PPR) has been widely used in the production of hot‐water pipes. To further improve its toughness and thermal resistance, β‐nucleating agents (β‐NAs) are frequently incorporated. In this study, PPR containing 5.6 mol % ethylene units was modified by two kinds of β‐NAs, that is, calcium pimelate and N,N ′‐dicyclohexylterephthalamide. The notched Izod impact strength of PPR increased with the addition of the β‐NAs. Drastically different toughening effects were found between the two β‐NAs. The structure of PPR with and without a β‐NA was investigated by calorimetry, X‐ray diffraction, and thermomechanical analysis. The results indicated that the relative fraction of β crystals ( k β ) in the injection‐molded specimens was determined by the type and content of β‐NA. The relationship between k β and the impact toughness was summarized. A critical value for k β (0.68) was identified for the brittle–ductile transition of PPR. PPR with β‐NA having a k β greater than 0.68 displayed a higher impact strength than the other mixtures. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 42930.