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Theoretical Description of an Anomalous Elongation During Two‐Way Shape‐Memory Effect in Crosslinked Semicrystalline Polymers
Author(s) -
Dolynchuk Oleksandr,
Kolesov Igor,
Radusch HansJoachim
Publication year - 2014
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201400065
Subject(s) - elongation , materials science , crystallinity , isothermal process , crystallization , polymer , crystallization of polymers , polyethylene , constant (computer programming) , composite material , stress (linguistics) , high density polyethylene , thermodynamics , physics , linguistics , philosophy , computer science , ultimate tensile strength , programming language
Summary The present study is focused on theoretical explanation of an anomalous elongation arising during non‐isothermal crystallization of crosslinked semicrystalline polymers under constant load that represents the first stage of two‐way shape‐memory effect (SME) in these materials. The proposed theoretical approach allows calculating the free energy change of a specimen deformed under constant load and cooled down below crystallization temperature at constant cooling rate, i.e. in non‐isometric and non‐isothermal conditions, respectively. The theory was confirmed for a crosslinked high‐density polyethylene chosen as a model object. It was shown that aforementioned anomalous elongation may be observed when the orientation of chain folds in crystals generating at cooling under load is parallel to or makes a sharp angle with the stretch direction. The stress‐strain‐temperature relationship derived from the free energy change was used to fit the experimental findings of the two‐way SME in crosslinked high‐density polyethylene. The fitting curves have shown well agreement with the experimental values.