PVDF Mends

Journal of the Electrochemical Society, Vol 115, N l, pp. 49-51 Ribeiro, P. Giacometti, J. Raposo, M. I rat Mendes, J. (1991). Effect of the air humidity on the corona polarization of / - PVDF films. 7th Int. Symp. on Electrets, pp. 322-327 Schaffert, R. (1965). Electrophotography, The Focal Press, London, New York Sessler, G. Gerhard-Multhaupt, R. (1999). Electrets, third edition, Laplacian Press, Morgan Hill, California ... 

Figurs 1 Phase diagram of the PVDF/PMMA Mend . glaaa transiliaii lenperalure T, (64) ...

At first giaaoe. the amorphous phase of crystallized PVDF/PMMA Mends should be homogeneously mixed The two components are oompklely misdble at all possible ays tallizatian temperatures, and demising is inMMled from kinetic reasons when the temperature b lowered below (be UCST. There ate, however, a number of indications that... 

Both PVDF and PMMA exhibit several relaxations in dynamic mechanical measurements. In a temperature-dependent experiment, the relaxation at the highest temperature, called a relaxation, changes its location on the temperature scale gradually with composition (11,12]. This, on the one hand, indicates miscibility of the two polymers. On the other hand, this a relaxation must be linked with Ibe glass Iransition of the Mend. Some other relaxations do not shifl with composition they are discussed in more detail in the next section, where dielectric relaxation is treated. 

The hydrostatic pressure dependence of the glass iransition in PVDF/PMMA Mends has been reported on in (67]. The volume compressibilities of these materials decrease rather evenly with inaeasing PVDF oonleni and increasing pressure (15,16]. Typical values at 60 C are 28 GPs for PMMA at ambient pressure a 19 GPa for PVDF at 200 MPa. 

Blending with PMMA almost does not affect the locations of all these relaxations on the temperature or frequency scale, respectively (Fig. 4 (S6-60.72.73]). IMth respect to the a a 7 relaxations, ihn is in accordance with the proposed molecular origins, since crystalline relaxations cannot be influenced by Mending. The relaxation, however, should change evenly with temperature after addition of PMMA between the f/s of the components (7,(PVDF) —40 7,(PMMA) " IKTC] if it is really doe to the glass... 

As it has been outlined in the introduction to this chapter, blending can be an interesting tool to improve performance properties of a material. Some attempts have been made by Mending with PMMA to meet this objective with respect to the electroaclivity of PVDF. The background of these works is that ... 

On the one hand, this nuy be because in fact blend-induced changes in (erroelectricity can be studied best with FVDF/PMMA blends, but, on the other band, may be due to the experience that the ferroelectric properties of this blend are in general worse than those of the pure polymer. Moreover, all that can be observed with such other Mends can be understood and explained by the structural and dynamic features and models developed from the findings on PVDF/FMMA blends. 

S. Wii. Entanglement between diwunilar chains in compatible polymer Mends PMMA and PVDF.i. Polymer ScL Part B Polymer Pkys. 25 337 (1987). 

B. R. Hahn. O. Hcrrmann-Schtaherr, and J. H. Wendorff. Evidence for crystal-amorphous interphase in PVDF and PVDF/PMMA Mends, Polymer 28 201 (1987). 

Y. Ando. D. Y. Yoon. Dielectric characicrizatiao of cryatal-amotphout ioterphaK in tcnii-cryttalUne PVDF and PVDF/PMMA Mends. ACS Din Polymer Chem. Polymer Prep., 28 26(1988). 

D. J. Woan. J. L Scheinbeim. and P. R. Couchman. The pressure dependence of the glass tnnsiton in PVDF/PMMA Mends. Bull APS 293/91 (1983X... 

F. Schal ier and B.-J. Jungnickel. The permittivities of PVDF/PMMA Mends at hydrostatic pressure, J. MocromoL ScL B—Pkys. 12 343 (1993X... 

D. Song. D. Yang, and 2 Feng, Formation of P-phase microcrystals from the melt of PVDF-PMMA Mends induced by quenching. /. Mol ScL 25 57 (1990)... 

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