Elastic properties and mechanical relaxation behaviors of PVDF (poly (vinylidene fluoride)) at temperatures between −20 and 100 °C and at 2 MHz ultrasonic frequency

Abstract

The elastic properties of PVDF have been investigated as a function of temperature. The propagation velocity and absorption of longitudinal and transverse ultrasonic waves have been measured at a constant frequency of 2 MHz and temperatures between –20 and 100 °C. Hence, the temperature dependences of storage and loss elastic constants have been obtained for temperatures between –20 and 100 °C. It has been seen that the relaxation behavior is affected from the form of mechanical disturbance. For the longitudinal mode, only one relaxation peak at 42 °C, but for transverse mode three relaxation peaks at 28 °C, 60 °C, and 94 °C have been observed. The results have been compared with the literature values obtained previously for PVDF. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2862–2873, 2005

The effect of uniaxial orientation on the dielectric relaxation behavior of α‐PVDF

“…This step is due to the secondary glass transition, which is observed in some semicrystalline polymers, and is defined as the upper glass transition T g ( U ). This transition is attributed to the rotational and translational motions of the tie molecules in the crystalline–amorphous interphase 1, 3, 23, 29. The decrease in the magnitude of the c p step with the draw ratio indicates that the number of mobilizable tie molecules in the crystalline–amorphous interphase decreased with drawing.…”

“…Two relaxation transitions (α and β), which shifted toward high temperatures due to the increase in the frequency, were observed as expected 36. It is known that, the α‐relaxation transition is the result of rotational and translational motions of the molecules in the crystalline regions, whereas the β‐relaxation transition belongs to the glass transition of the amorphous fraction 3, 10, 12, 22, 23, 27, 29…”

“…Unoriented PVDF (FV 301460) films with dimensions of 300 × 300 × 0.8 mm 3 and a density of 1.76 g/cm 3 supplied by Goodfellow (Cambridgeshire, England), were used. The unoriented film in the α‐crystalline phase is shown by DSC and X‐ray diffraction measurements in a previous paper 29. Drawing samples with the size of 200 × 20 × 0.8 mm 3 were cut from the main sample.…”

Elastic properties of poly(vinyldene fluoride) (PVDF) crystals: A density functional theory study

“…1 Over past several decades, PVDF has been subjected to intensive studies. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] To date, it is known the PVDF exhibits four crystalline phases, namely: a, b, c, and d phases.…”

Effects of B2 O3 addition on structural and dielectric properties of PVDF

“…PVDF has four different crystalline modifications (α, β, γ, and δ) . Transitions from α‐phase to β, γ, and δ phases can be possible with procedures such as annealing at high pressure and temperature, draw at low and high temperatures, polarization at high electric field . PVDF is used in various areas of technology due to its high chemical resistance, good stability, at high‐level permittivity, and piezoelectric property .…”