Polyvinylidene fluoride (PVDF) is a modern polymer material used in a wide variety of ways. Thanks to its excellent resistance to chemical or thermal degradation and low reactivity, it finds use in biology, chemistry, and electronics as well. By enriching the polymer with an easily accessible and cheap variant of graphite, it is possible to affect the ratio of crystalline phases. A correlation between the ratios of crystalline phases and different properties, like dielectric constant as well as piezo- and triboelectric properties, has been found, but the relationship between them is highly complex. These changes have been observed by a number of methods from structural, chemical and electrical points of view. Results of these methods have been documented to create a basis for further research and experimentation on the usability of this combined material in more complex structures and devices.

Currently, there is an ever-growing interest in carbon materials with increased deformation-strength, thermophysical parameters. Due to their unique physical and chemical properties, such materials have a wide range of applications in various industries. Many prospects for the use of polymer composite materials based on polyvinylidene fluoride (PVDF) for scientific and technical purposes explain the plethora of studies on their characteristics “structure-property”, processing, application and ecology which keep appearing. Building a broader conceptual picture of new generation polymeric materials is feasible with the use of innovative technologies; thus, achieving a high level of multidisciplinarity and integration of polymer science; its fundamental problems are formed, the solution of which determines a significant contribution to the natural-scientific picture of the modern world. This review provides explanation of PVDF advanced properties and potential applications of this polymer material in its various forms. More specifically, this paper will go over PVDF trademarks presently available on the market, provide thorough overview of the current and potential applications. Last but not least, this article will also delve into the processing and chemical properties of PVDF such as radiation carbonization, β-phase formation, etc.

Modern material science often makes use of polyvinylidene fluoride thin films because of various properties, like a high thermal and chemical stability, or a ferroelectric, pyroelectric and piezoelectric activity. Fibers of this polymer material are, on the other hand, much less explored due to various issues presented by the fibrous form. By introducing carbon nanotubes via electrospinning, it is possible to affect the chemical and electrical properties of the resulting composite. In the case of this paper, the focus was on the further improvement of interesting polyvinylidene fluoride properties by incorporating carbon nanotubes, such as changing the concentration of crystalline phases and the resulting increase of the dielectric constant and conductivity. These changes in properties have been explored by several methods that focused on a structural, chemical and electrical point of view. The resulting obtained data have been documented to create a basis for further research and to increase the overall understanding of the properties and usability of polyvinylidene fluoride fiber composites.

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The method of inclusion of various additives into a polymer depends highly on the material in question and the desired effect. In the case of this paper, nitride salts were introduced into polyvinylidene fluoride fibers prepared by electrospinning. The resulting changes in the structural, chemical and electrical properties of the samples were observed and compared using SEM-EDX, DSC, XPS, FTIR, Raman spectroscopy and electrical measurements. The observed results displayed a grouping of parameters by electronegativity and possibly the molecular mass of the additive salts. We virtually demonstrated elimination of the presence of the γ-phase by addition of Mg(NO3)2, Ca(NO3)2, and Zn(NO3)2 salts. The trend of electrical properties to follow the electronegativity of the nitrate salt cation is demonstrated. The performed measurements of nitrate salt inclusions into PVDF offer a new insight into effects of previously unstudied structures of PVDF composites, opening new potential possibilities of crystalline phase control of the composite and use in further research and component design.

This paper is focused on failure monitoring in lightweight concrete (special high-performance concrete that contains porous aggregate with a low bulk density) with high-strength polypropylene fibers under mechanical loading. The aim was to determine how the cracks' generation intensity in the tested concrete samples depends on the fibers' length and quantity. Our diagnostic method is based on a measurement of the acoustic and electromagnetic emission signals, which occur when solid dielectric materials are mechanically stressed. Several groups of lightweight concrete samples with various types and concentrations of high-strength polypropylene fibers were prepared for our experiment. We made two-channel measurements of the concrete samples from each group for defined loading conditions. The first channel was electromagnetic emission (EME) and the second was acoustic emission (AE). The electromagnetic emission and acoustic emission methods are promising methods to study the generation and behavior of cracks. The main advantage of EME and AE is their ability to be detected already in the stressed stage, which prevents macroscopic deterioration in solids. From the obtained results it can be concluded that the generated cracks' intensity is significantly affected by the presence of polypropylene fibers and by their length and dosage. Keywords: acoustic emission, electromagnetic emission, lightweight concrete, fiberŝ lanek je usmerjen na pregled po{kodb pri mehanskem obremenjevanju lahkega betona (poseben visoko zmogljiv beton, ki vsebuje porozne sestavine z majhno gostoto), z visokotrdnostnimi polipropilenskimi vlakni. Namen je bil ugotoviti, kako je intenziteta nastanka razpok odvisna od dol`ine in koli~ine vlaken. Diagnosti~na metoda je temeljila na merjenju akusti~nih signalov in signalov elektromagnetne emisije, ki se pojavijo kadar je trden dielektri~ni material mehansko obremenjen. Za eksperiment je bilo pripravljenih ve~vrst lahkih betonov z razli~no vrsto in koncentracijo visokotrdnostnih polipropilenskih vlaken. Pri dolo~enih pogojih obremenitve smo izvr{ili dvokanalne meritve vzorcev betona iz vsake skupine. Prvi kanal je bila elektromagnetna emisija (EME), drugi pa akusti~na emisija (AE). Metodi elektromagnetne emisije in akusti~ne emisije sta obetajo~i metodi za {tudij nastanka in obna{anja razpok. Glavna prednost EME in AE je, da ju je mogo~e odkriti`e med stanjem napetosti, kar prepre~i lokalne makroskopske po{kodbe v trdnem stanju. Iz dobljenih rezultatov je mogo~e zaklju~iti, da je intenzivnost nastajanja razpoke mo~no odvisna od prisotnosti polipropilenskih vlaken, od njihove dol`ine in odmerka. Klju~ne besede: akusti~na emisija, elektromagnetna emisija, lahki beton, vlakna

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The paper deals with the analysis of the fractal dimension of fracture surfaces of concrete specimens tested in a three-point bending configuration. Fifteen representative specimens were chosen out of a bigger set for the fractal dimension analysis. Their fracture surfaces were scanned by 2D optical profilometry and analysed by the FracDiM software created in the Java programming language. The resulting values of fractal dimensions for specimens of three different sizes are presented.