Poly-vinylfluoride

PVFas [FLUORINE COMPOUNDS, ORGANIC - POLY(VINYLFLUORIDE)] (Vol 11)... 

Just as an example, the X-ray diffraction patterns of compression moulded samples of PVDF, poly(vinylfluoride), and of some VDF-VF copolymers of different compositions are shown in Fig. 17 [90]. The degrees of crystallinity of the copolymer samples (40-50%) are high and analogous to those of the homopolymer samples. This indicates a nearly perfect isomorphism between the VF and VDF monomeric units [90, 96], The diffraction patterns and the crystal structures of the copolymers are similar to those of PVF, which are in turn similar to the X-ray pattern and crystalline structure of the P form of PVDF. On the contrary, the X-ray pattern of a PVDF sample crystallized under the same conditions (Fig. 17 a) is completely different, that is typical of the non-piezoelectric a form [90]. 

Ferroelectric properties (much weaker than PVF2) are shown also by other polymers like poly(vinylchloride) (PVC) or poly(vinylfluoride) (PVF). (See Table 48.3 for... 

These nebulizers and their components are typically constructed from polymer materials, such as polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), or poly-vinylfluoride (PVF), although some designs are available in borosilicate glass or quartz. The excellent corrosion resistance of the polymer nebulizers means they have naturally low blank levels. This characteristic, together with their ability to handle small sample volumes found in applications such as vapor phase decomposition (VPD), makes them an ideal choice for semiconductor laboratories that are carrying out ultratrace element analysis. - A microflow concentric nebulizer made from PFA is shown in Figure 3.8, and a typical spray pattern of the nebulization process is shown in Figure 3.9. 

Sundhohn and co-workers [128-131] reported the preparation of PCMs by direct sulfonation of poly(vinylfluoride) (PVF) by means of irradiation with heavily charged particles (protons or electrons) prior to sulfonation. The obtained membranes (PVF-g-SA) displayed ionic conductivities up to 20 mS cm". The state of water [132] and the structure [133] of these membranes were established. The water swelling properties of such membranes was lower than Nafion 117 and 112. Interestingly, PEMFC tests with these membranes showed better performance than Nafion 117 membranes, unlike Nafion 112, which performed better than PVF-g-S A membranes [134]. However, these membranes failed after 200 h of testing due to membrane rupture between the membrane active area and the gasket. 

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