Influences of crystallization histories on PTC/NTC effects of PVDF/CB composites

✍ Scribed by Mingyin Zhang; Wentao Jia; Xinfang Chen

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 422 KB
• Volume: 62
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/(sici)1097-4628(19961031)62:5<743::aid-app4>3.0.co;2-w

✦ Synopsis

Two switching phenomena of poly(viny1idene fluoride) (PVDF) containing carbon black (CB) with different crystallization histories are studied. Both the percolation threshold (apt) and the critical concentration of the positive temperature coefficient (PTC) materials (@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 a n important role in modifying the shape of the resistivitytemperature ( p -T ) curves. The PTC and NTC intensities of these systems, whose CB contents lie between @pc and @c, increase with increasing crystallinity, which are realized by altering the crystallization histories of the matrices.