PP-based composites with two mineral fillers (perlite or glass beads) were manufactured by extrusion, and then subjected to orientation in a ratio of 3:1. Electrets were obtained in the polarization process under the influence of a constant electric field. Sample morphology was tested by SEM whereas the crystallinity was determined by XRD. Mechanical strength and thermal stability of composites was studied by tensile tests and thermogravimetric analysis, respectively. The piezoelectric characteristics were appointed by measurement of the electrical charge and current voltage in the polarized samples. The dependence of thermally stimulated depolarized current (TSDC) on temperature was also investigated. The piezoelectric coefficient (d33), the electret stability over time as well as activation energy of depolarization process have been determined. It was found that low filler content (i.e. 2.5 and 5 wt.% of glass beads and perlite, respectively) significantly improve piezoelectric properties of isotactic polypropylene (i-PP).
A study has been made on the uphill transport of zinc cations across a multimembrane hybrid system (MHS) composed of two ion-exchange membranes (IEM) separated by a bulk liquid membrane (BLM). The fluxes of the Zn(II)/H countertransport were investigated as dependent on the composition and structure of ion-exchange polymer membranes (i), the solvent of a liquid membrane (ii), the feed and strip membrane area ratio (iii), and the pH of the feed solution (iv). The IEMs of various ionogenic groups (sulfonic acid, carboxylic acid, quaternized amine) and of various structure (clustered, gelatinous, porous) were examined in the MHS containing the BLM with di(2-ethylhexyl)phosphoric acid as a carrier of Zn(II) cations. It has been found that the Zn(II) fluxes are dependent on the properties of both the BLM and polymer membranes, i.e., on the BLM solvent viscosity (i), the nature and concentration of the IEM ion-exchange sites (ii), and the IEM thickness (iii). The best results were obtained when using hexane as the BLM solvent and the Nafion-117 membrane (perfluorinated polymer, sulfonic acid groups) as the cation-exchange membrane (CEM). The influence of the area ratio (feed-to-strip interface) has been checked for A f /A g equal to 3:1, 1:1, and 1:3. It was found that the asymmetry of the system leads mainly to some changes in the accumulation of transported species in a liquid membrane phase.
Transport of sulfates of divalent metals [M = Mn(II), Cu(II), Co(II), Ni(II)] in a system made up of multicomponent solution of MS04\Nafion membranelsulfuric acid solution was studied. It was found that Donnan dialysis results in a recovery factor amounting to 8040% with the concentration ratio C~,~t~i~l C~, f~~d not less than 30. The results of M(II)/H countertransport were compared with the results of simple dialysis of single and multiionic solutions. The technique of Donnan dialysis is efficient in preconcentrating ions for further separation in a multimembrane hybrid system employing a specific camer of ions.
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