Processing–property interactions in poly(vinylidene fluoride). II. Morphology and property characterization of extruded films

Khomami, Bamin; McHugh, A. J.

doi:10.1002/app.1988.070360411

Cited by 4 publications

(2 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This was in agreement with results reported by other workers. 7,22 The piezoelectric properties of the polarized PVDF films significantly depended on the b-phase content. 10,14 The d 33 values of the films prepared with both dies after cold drawing to two different draw ratios are reported in Table III.…”

Section: Resultsmentioning

confidence: 99%

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

Sobhani

Razavi‐Nouri

Yousefi

2007

J of Applied Polymer Sci

View full text Add to dashboard Cite

This study was devoted to the effect of extensional flow during film extrusion on the formation of the b-crystalline phase and on the piezoelectric properties of the extruded poly(vinylidine fluoride) (PVDF) films after cold drawing. The PVDF films were extruded at different draw ratios with two different dies, a conventional slit die and a two-channel die, of which the latter was capable of applying high extensional flow to the PVDF melt. The PVDF films prepared with the two-channel die were drawn at different temperatures, strain rates, and strains. The optimum stretching conditions for the achievement of the maximum b-phase content were determined as follows: temperature ¼ 908C, strain ¼ 500%, and strain rate ¼ 0.083 s À1. The samples prepared from the dies were then drawn under optimum stretching conditions, and their b-phase content and piezoelectric strain coefficient (d 33 ) values were compared at equal draw ratios. Measured by the Fourier transform infrared technique, a maximum of 82% b-phase content was obtained for the samples prepared with the two-channel die, which was 7% higher than that of the samples prepared by the slit die. The d 33 value of the two-channel die was 35 pC/N, which was also 5 pC/N higher than that of the samples prepared with the slit die.

show abstract

Section: Resultsmentioning

confidence: 99%

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

Sobhani

Razavi‐Nouri

Yousefi

2007

J of Applied Polymer Sci

View full text Add to dashboard Cite

show abstract

“…It has been shown that the crystal modulus of the β form along the chain direction is 192 GPa at room temperature, as determined by WAXD 5. Although extensive studies have been made on the uniaxial drawing of PVDF, the moduli achieved have typically been in the range of 3.5–6.5 GPa 6, 8, 27, 28. Nakagawa and Amano29 applied a microwave‐heated drawing technique TO a PVDF rod and obtained an oriented rod with a higher tensile modulus of 7.6 GPa.…”

Section: Resultsmentioning

confidence: 99%

Effect of annealing on the structure and properties of poly(vinylidene fluoride) β‐form films

Nakamura

Sawai

Watanabe

et al. 2003

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

Oriented poly(vinylidene fluoride) (PVDF) films consisting of ␤ crystals were prepared by the solid-state coextrusion (SC) of a gel film near the melting temperature (T m ) and by conventional cold tensile drawing (TD) of a melt-quenched film. These films were annealed over the temperature range of 75-190°C (below and above the static T m ) while the sample length was kept constant or constant loads were applied. After annealing with the sample length kept constant, the dynamic Young's modulus markedly decreased because of the relaxation of oriented amorphous chains, as shown by infrared spectroscopy. In contrast, annealing under a constant load improved the chain orientation in both the crystalline and amorphous regions, resulting in an increase in the modulus from an initial 10.5 to 14.3 GPa for the SC and from an initial 3.3 to 4.8 GPa for the TD. The SC, annealed at 190°C with a constant load corresponding to an initial tension of 200 MPa, exhibited an extreme crystalline-chain orientation of 0.998 and a modulus of 14.3 GPa, among the highest values ever reported for PVDF. Although the remanent polarization (P r ) of the TD increased slightly from the initial 62 to 68 mC/m 2 , P r of the SC stayed constant at 100 mC/m 2 independently of the annealing conditions. This suggests that the P r value of 100 mC/m 2 approached the equilibrium value for this PVDF sample containing 3.5 mol % structural defects. Therefore, although the modulus and P r of the TD increased slightly with annealing, the maximum values achieved by annealing were markedly lower than those of the SC and annealed SC.

show abstract

Continuous extrusion of self‐reinforced high density polyethylene

Huang¹

1998

Polymer Engineering & Sci

View full text Add to dashboard Cite

Continuous extrusion was studied of self-reinforced high density polyethylene (HDPE) sheets from flow-induced crystallization at die pressures varying from 30 to 60 MPa. Their morphology, thermal behavior, tensile strength, and light transmittance were tested. Flow fields of a polymer melt through a converging wedge channel were also investigated by direct visual observations in conjunction with a theoretical analysis. The extensional strain rate increased abruptly as the melt approached the exit of the converging channel, this resulting in a higher crystallization rate. So, achieving the crystallization of molecular chains just in front of the exit of the converging channel may favor to extrude the bulk polymeric materials having high properties under lower pressures (e.g., 40 MPa or lower), this having been realized in the present work. The tensile strength of the self-reinforced HDPE sheet prepared at a 40 MPa pressure was enhanced by a factor of 8.

show abstract

Processing–property interactions in poly(vinylidene fluoride). II. Morphology and property characterization of extruded films

Cited by 4 publications

References 19 publications

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

Effect of annealing on the structure and properties of poly(vinylidene fluoride) β‐form films

Continuous extrusion of self‐reinforced high density polyethylene

Contact Info

Product

Resources

About