Structural evolution of PVDF during storage or annealing

• Published in: Polymer (Guilford) Vol. 45; no. 5; pp. 1679 - 1688
• Main Authors: Neidhöfer, M, Beaume, F, Ibos, L, Bernès, A, Lacabanne, C
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.03.2004; Elsevier
• Subjects: aging; annealing; Applied sciences; Chemical Sciences; Crystallization; Exact sciences and technology; Organic polymers; Physicochemistry of polymers; Polymers; Properties and characterization; Secondary crystallization; annealing; Secondary crystallization; aging; Beta form; Vinylidene fluoride polymer; Kinetics; Experimental study; Thermal annealing; Isothermal crystallization; Alpha form; Aging; Annealing
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2003.12.066

The effect of annealing PVDF at temperatures above Tg and below Tm was investigated by differential scanning calorimetry (DSC), thermostimulated current spectroscopy (TSC) and solid-state NMR. This study evidences a progressive structural evolution, taking place during such annealing. Its characteristics (kinetics and its temperature dependence, lack of reversibility at lower temperature over extended periods of time, double organization corresponding to double annealing with unmodified kinetics) point to a mechanism of secondary crystallization as described by Marand et al. In addition to the formation of extra crystalline (hence rigid) material, this phenomenon is believed to generate increasing conformational constraints in the residual amorphous material. Accordingly, a progressive reduction of the molecular mobility was demonstrated by NMR during annealing.