Nonmonotonic dielectric relaxation behavior of thermochromic epoxy composite

•Nonmonotonic dielectric relaxation is observed in thermochromic epoxy composites.•The origin is proposed to be the phase transformation of solvent in microcapsules.•Confined system model is utilized for the mechanism interpretation.•The phase transformation would decrease the free volume for relaxa...

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Bibliographic Details
Published in:Materials letters 2022-04, Vol.312, p.131678, Article 131678
Main Authors: Gao, Jian, Long, Yiwei, Wu, Kangning, Li, Jianying, Yin, Guilai
Format: Article
Language:English
Subjects:
Chain mobility
Confined system
Dielectric relaxation
Fabric analysis
Materials science
Nonmonotonic dielectric relaxation
Phase transformation
Phase transitions
Polymeric composites
Relaxation time
Rotational states
Solvents
Temperature dependence
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Summary:•Nonmonotonic dielectric relaxation is observed in thermochromic epoxy composites.•The origin is proposed to be the phase transformation of solvent in microcapsules.•Confined system model is utilized for the mechanism interpretation.•The phase transformation would decrease the free volume for relaxation processes. An unusual nonmonotonic relaxation behavior is observed in thermochromic epoxy composites. The relaxation time first decreases with temperature and then abnormally increases from 331 K to 337 K, exhibiting a saddlelike temperature dependence. The nonmonotonic relaxation behavior is proposed to originate from the phase transformation of solvent in microcapsules based on the model of confined system. It is evidenced that from 331 K to 339 K the solvent is in rotational state with increased interchain distances and chain mobility. This could decrease the free volume given for relaxation in microcapsules and consequently result in the increase of relaxation time.
ISSN:0167-577X
1873-4979
DOI:10.1016/j.matlet.2022.131678