Resumo Neste trabalho partículas de níquel foram incorporadas através da mistura física do pó resultante da mistura PVDF/Pani obtido por síntese química. Filmes homogêneos foram obtidos através da prensagem a temperatura de 180°C. A partir dos resultados pode-se notar alterações favoráveis e desfavoráveis nas propriedades do compósito após a incorporação e como estas tornam-se dependentes da incorporação. Os resultados de difratometria apresentaram picos característicos tanto da fase α da matriz polimérica e das partículas de níquel, e juntamente com as analises térmicas, que não há alteração na estrutura conformacional e a configuracional. Mesmo apresentando uma boa estabilidade térmica a incorporação indica que além da presença do polímero condutor como o aumento de partículas são prejudiciais às propriedades mecânicas finais da amostra. As micrografias apresentam as partículas de forma dispersas ao longo do filme e determinantes para os valores de condutividade elétrica e obtenção de uma fase magnética.

Abstract In this work nickel particles were incorporated by physically mixing of resulting powder blends of PVDF/Pani, obtained by chemical synthesis. Homogeneous films were obtained by hot pressing at 180 °C. From the results could be noted favorable and unfavorable changes in the properties of composites after incorporation and how this become dependent of the incorporation. The results of diffraction showed the characteristic peaks of both the α phase of the polymer matrix and the nickel particles, and with thermal analysis, no change in the conformational structure and configurational. Even with a good thermal stability incorporating, indicates that besides the presence of the conducting polymer as the increase of particles are harmful to the final mechanical properties of the sample. Micrographs showed particles dispersed throughout the film and determinants to electrical conductivity values and achieving a magnetic phase.

A composite of natural rubber (NR) with polyaniline (PANI) was obtained by mixing an aqueous dispersion of dodecylbenzenesulfonic acid (DBSA)-doped PANI with NR latex in different concentrations. Films were obtained by the casting method and characterized by ultraviolet visible near-infrared (UV-Vis-NIR) spectroscopy, thermogravimetry/differential thermogravimetry (TG/DTG), stress-strain testing, differential scanning calorimetry (DSC), and DC electrical conductivity measurements. The UV-vis-NIR spectrum showed that PANI remained doped in the composite, and this improved the mechanical and electrical proprieties of NR films and afforded them good thermal stability up to ~200ºC. The percolation threshold did not follow the universal critical exponent, and in this case, conduction preferentially occurs by hopping and tunneling.

Poly(vinylidene fluoride)/polyaniline blends of different composition were synthesized by chemical polymerization of aniline in a mixture of Poly(vinylidene fluoride) and N,N-dimethylformamide and their thermal and mechanical behavior was investigated as a function of the polyaniline doping level and the composition using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis and tensile tests techniques. The results showed the blend obtained presents a good thermal stability with low weight loss up to 300 ºC, assigned to water and solvents evaporation. The glass transition and melting point is not affected by the PANI content in the blend, showing that polymers are no miscible. The films produced present a good sustainability; however the presence of the conducting polymer in the blend increases the tensile strength and the Young modulus, while diminishes the elongation at break, as compared to pure PVDF.

Flexible, free-standing piezo and pyroelectric composite with 0 to 3 connectivity was made up from Lead Zirconate Titanate (PZT) powder and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) copolymer. The pyroelectric and the piezoelectric longitudinal (d33) coefficients were measured. A 50/50 vol.% PZT/PVDF-HFP composite resulted in piezo and pyroelectric coefficients of d33 = 25.0 pC/N and p = 4.5 × 10-4 C/m²K at 70 °C, respectively. Analysis of the complex permittivity in a wide range of frequency was carried out indicating lower permittivity of the composite in comparison with a permittivity of the PZT ceramic. The low value of the permittivity gives a high pyroelectric figure of merit indicating that this material can be used to build a temperature sensor in spite of the lower pyroelectric coefficient compared with PZT.

Neste trabalho estudou-se o efeito das condições de preparação na condutividade elétrica de blendas condutoras de poli(fluoreto de vinilideno) (PVDF) com poli(o-metoxianilina) (POMA). A condutividade elétrica e a qualidade dos filmes produzidos dependem significativamente do solvente, dopante e das condições de preparação das blendas. Filmes flexíveis e auto-sustentáveis da blenda PVDF/POMA dopada com o ácido p-tolueno sulfônico (TSA) foram obtidos em condições otimizadas. Estes apresentam condutividade elétrica em uma larga faixa (10-12 - 10-2 S/cm), onde para baixos teores de POMA-TSA (<2,0% em massa) já se atinge alto valor de condutividade (10-7 S/cm), não sendo definida uma composição mínima para percolação.

In this work, the effect of preparation conditions on the properties of conductive blends of poly (vinylidene fluoride) (PVDF) and poly(o-methoxyaniline) (POMA) was studied. The quality and conductivity of the films produced depend significantly on the solvent, dopant and preparation conditions of the blends. Flexible, free-standing films of PVDF/POMA blends doped with p-toluene sulfonic acid (TSA) were obtained in optimized conditions. These blends can exhibit electrical conductivity in a wide range (10-12 - 10-2 S/cm). Furthermore, relatively high conductivity values (10-7 S/cm) are reached starting from low contents of POMA-TSA (<2,0% weight) without definition of a percolation threshold.