Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanocomposites with different contents of nanoclays were prepared by melt mixing. The clays used included unmodified clays, a commercially available hydrophilic nanoclay based on bentonite (nanoclay 1) and organically modified clay based on montmorillonite (nanoclay 2). The nanocomposites obtained were analyzed by x-ray diffraction, differential thermal and differential scanning calorimetry analyses and their basic tensile and other characteristics were determined. The distribution of the filler throughout the matrix was found to be good for both the types of nanocomposite materials. Nanoclay 1 induced slight increase in the b-phase and higher deviation of the main diffractions (2 ¼ 18.6 and 20.1 at 10 mass% filler). The degree of crystallinity of the materials containing nanoclay 2 decreased from 26.4 to 20.5% and from 23.9 to 18.7%, respectively, for the first and second heating. The tensile strength of the materials based on PVDF-HFP with nanoclays 1 and 2 was close to that of the initial copolymer or slightly increased with the addition of nanoclay 2. Young's modulus was in the range of 215-265 MPa. The heat resistance by Vicat increased by 7 C compared with the initial copolymer.
Nanocomposite materials based on vinylidene fluoride-hexafluoropropylene copolymer and organically modified montmorillonite Cloisite ® 15A were prepared by two different methods: melt mixing and co-precipitation. The changes taking place in crystalline structure, tensile strength, thermal behavior and the formation of piezoelectric β -phase as a result of the polymer system dissolution in dimethyl sulfoxide were studied. The technological specificity of each method has certain effect on the properties of the obtained nanocomposites. The highest content of β -phase -95 % was achieved by co-precipitation from the solution of vinylidene fluoride-hexafluoropropylene copolymer in dimethyl sulfoxide and 6 mass % content of Cloisite ® 15A. Despite the common view that the use of solvents and prolonged technological procedure lead to overall higher expenses, the obtained nanocomposites could be promising for the preparation of new piezo-materials.
The process of photooxidative destruction of high density polyethylene films containing different organic complexes of polyvalent metals as pro-oxidant additives after UV-irradiation was studied. During exposure to UV-irradiation, the more significant changes in the mechanical and thermal properties were detected for the foils containing pro-oxidant additives compared to initial high density polyethylene. This indicated for the higher degree of oxidation in these samples and confirmed the effectiveness of thеsе additives in promoting the oxidation of high density polyethylene during UV-irradiation. It was found that the decrease of the strength of the initial high density polyethylene foils was more pronounced for the samples with pro-oxidants cobalt (III) acetylacetonate and manganese (II) acetylacetonate. The use of 2 mmol/kg iron (III) acetylacetonate and 4 mmol/kg cobalt (III) acetylacetonate as pro-oxidants gave the highest decrease of elongation at break of the polyethylene foils.
Different blends of virgin, recycled polyethyleneterephthalate (5-20 mass %) and their mixtures used for textile fibers were prepared. Their rheological characteristics were studied at temperatures 543, 548 and 553 K and shear stresses in the range from 6.2x10 3 to 14x10 3 Pa. Drawing the flow curves for the melts of the polymers studied using experimental data, it was found that they obeyed the power law at the three temperatures. A weak tendency of increase of the flow index was observed with the increase of temperature. The effects of two different stabilizers (Irganox 1076 and butylated hydroxytoluene BHT, 0.5 mass% vs. the polymer material) on the thermooxidative degradation were studied. The stabilizing ability of Irganox 1076 was found to be the better one since it increased viscosity from 50 to 100 Pa.s without any significant changes in polyethyleneterephthalate appearance. The influence of processing reiteration was studied for the individual polymers, as well as for their mixtures in different ratios.
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