Premium
Influences of crystallization histories on PTC/NTC effects of PVDF/CB composites
Author(s) -
Zhang Mingyin,
Jia Wentao,
Chen Xinfang
Publication year - 1996
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/(sici)1097-4628(19961031)62:5<743::aid-app4>3.0.co;2-w
Subject(s) - crystallization , crystallinity , temperature coefficient , materials science , composite material , percolation (cognitive psychology) , carbon black , fluoride , chemical engineering , polymer chemistry , chemistry , inorganic chemistry , natural rubber , neuroscience , engineering , biology
Two switching phenomena of poly (vinylidene fluoride) (PVDF) containing carbon black (CB) with different crystallization histories are studied. Both the percolation threshold (Φ pc ) and the critical concentration of the positive temperature coefficient (PTC) materials (Φ c ) increase as the crystallization temperature declines. PTC and the negative temperature coefficient (NTC) effect become obvious when the cooling speed is reduced. The morphologies of PVDF crystals play an important role in modifying the shape of the resistivity‐temperature (ρ‐ T ) curves. The PTC and NTC intensities of these systems, whose CB contents lie between Φpc and Φc, increase with increasing crystallinity, which are realized by altering the crystallization histories of the matrices. © 1996 John Wiley & Sons, Inc.