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Relationship of polymorphic crystalline phase texture to strain recovery and stiffness of a propylene‐based elastomer
Author(s) -
Dias P.,
Kazmierczak T.,
Chang A.,
Ansems P.,
Van Dun J.,
Hiltner A.,
Baer E.
Publication year - 2009
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.29823
Subject(s) - materials science , elastomer , crystallinity , composite material , ultimate tensile strength , lamellar structure , copolymer , recrystallization (geology) , thermoplastic elastomer , coalescence (physics) , amorphous solid , polymer , crystallization , crystallography , chemical engineering , chemistry , paleontology , physics , astrobiology , engineering , biology
Abstract A stretching process to enhance the stiffness of an elastomeric propylene‐ethylene copolymer through orientation was examined. The tensile extension was performed at various temperatures within the unusually broad melting range of the copolymer. Stretching transformed the unmelted lamellar crystals into shish‐kebab fibers that acted as a scaffold for an elastomeric matrix of entangled, amorphous chains. Density measurements indicated that the process did not significantly affect the amount of crystallinity, which was about 23%. If the specimen was recrystallized by cooling after it recovered from the stretched state, the amount of orientation decreased with increasing stretching temperature. However, if recrystallization occurred in the stretched state, it led to the formation of a second crystalline network that prevented contraction of the oriented crystalline structure during strain recovery. It was suggested that the second network was anchored by α′‐PP daughter lamellae that crystallized epitaxially on the α‐PP mother crystals of the extended fibrils. Although the manner in which the films were stretched and recrystallized strongly affected the modulus, good elasticity of the stretched films revealed the persistence of an elastomeric network. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009