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Effect of morphology on stress relaxation of polypropylene
Author(s) -
Attalla G.,
Guanella I. B.,
Cohen R. E.
Publication year - 1983
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760231605
Subject(s) - materials science , crystallinity , relaxation (psychology) , polypropylene , tacticity , stress relaxation , superposition principle , activation energy , composite material , modulus , morphology (biology) , stress (linguistics) , viscoelasticity , polymer , creep , chemistry , polymerization , mathematics , psychology , social psychology , linguistics , philosophy , biology , genetics , mathematical analysis
Abstract Samples of isotactic polypropylene having different morphologies and crystallinities were prepared and subjected to stress‐relaxation experiments at different levels of strain. The relaxation moduli were determined in the range of temperature between – 20 and 40°C over a period of time from 1 to 1000 seconds. Using the time‐temperature superposition principle, the activation energy values of the shift factors a T were determined and the master curves were obtained for the various structures. Increasing crystallinity and/or crystalline aggregate size increases the relaxation modulus of the material and changes both shape and location of the spectrum of relaxation times so that no simple method can be found to correlate the various master curves.