AbstrAct:Polyanilines have many applications in Aerospace, especially in their doped form. Studies on their synthesis in a pilot scale can contribute to obtain products with desirable characteristics for such applications. The present study reports the chemical oxidative synthesis of polyaniline in pilot scale and different reaction times in order to determine if there are variations in the polyaniline structure, morphology and conductivity due to these synthesis conditions. It is very common to analyze these data for polymers obtained through bench scale. However, several parameters change the properties of final material in major scales, such as thermal, mechanic and diffusive variables. Therefore, the reaction time is the only variable into the 9 syntheses carried out, and polyaniline is obtained in a doped form, being dedoped with ammonium hydroxide and redoped with dodecylbenzenesulphonic acid. The doped and redoped samples were characterized by their molecular structure, thermal behavior, crystallinity and morphology. The electrical conductivity of redoped samples was determined. Some differences in the structure and morphology of doped and dedoped forms, identifying the doping structures, were reported. This paper aims to present the relationship between changes on structure and morphology of doped and undoped polyaniline obtained by the mentioned experiments. Furthermore, some addicts on conductivity are carried out. It was possible to contribute in order to obtain a more conductive polyaniline in pilot scale.
Polycarbonate (PC)/acrylonitrile‐butadiene‐styrene copolymer (ABS) blend‐based multi‐wall carbon nanotubes (MWCNT) nanocomposites is an attractive alternative for the manufacture of electronics housing as it can have the mechanical and electromagnetic properties required for this application. The preferred location of MWCNT in PC/ABS blend is an important parameter to obtain better mechanical and electromagnetic properties. In this way, three different blending protocols (BP) were used to obtain PC/ABS/maleic anhydride‐grafted ABS (ABS‐g‐MAH) (85/10/5) blend‐based MWCNT nanocomposites with the addition of 0.5 and 1 wt% of MWCNT in a twin‐screw extruder. Specimens were evaluated by thermal (thermogravimetric analysis—TGA and differential scanning calorimetry—DSC), mechanical (Izod impact strength and tensile tests), dynamic mechanical analysis (DMA), electrical, and rheological properties, which were correlated with the nanocomposites morphology evaluated by high‐resolution scanning electron microscopy. The BP associated with the addition of a compatibilizer agent influenced the MWCNT distribution and location in the polymeric matrix. The one‐step extrusion process results in MWCNT mostly at the interface of the PC/ABS blend and agglomerates, leading to lower mechanical and thermal properties. The BP in which a PC/MWCNT masterbatch was first prepared and then diluted in ABS and ABS‐g‐MAH achieves the higher mechanical properties, increasing Young's modulus and the ultimate tensile strength. The third BP in which MWCNT was added in a second step in the blend already processed resulted in a homogeneous dispersion of MWCNT on both phases and a lower electrical resistivity.
Resumo Este trabalho apresenta um estudo comparativo dos comportamentos térmicos de três famílias de laminados de fibra de carbono/resina epóxi, submetidas a múltiplos ciclos térmicos, via análises termogravimétricas e dinâmico-mecânicas. Este estudo procura aliar a possibilidade de utilização de retalhos de pré-impregnados de fibra de carbono com resina epóxi - um material nobre na indústria aeronáutica, por meio da comparação do comportamento térmico de um laminado preparado com retalhos de pré-impregnados (laminado R), com outros dois laminados, sendo um manufaturado com prepreg comercial (laminado A) e um terceiro obtido por impregnação manual de reforço seco de fibra de carbono com resina epóxi (laminado B). Os laminados curados a 180 °C foram submetidos a múltiplos ciclos térmicos, totalizando 40, 100 e 300 h de exposição na temperatura máxima de 180 °C. As análises termogravimétricas mostram que os laminados submetidos às múltiplas ciclagens apresentam estabilidade térmica na temperatura de 180 °C, com perda de massa relativa à umidade absorvida pelos laminados. As análises dinâmico-mecânicas evidenciam que as múltiplas ciclagens térmicas afetam pouco ou até aumentam as temperaturas de transição vítrea dos sistemas de resinas epóxis estudados. A partir dos resultados obtidos pode-se afirmar que os laminados submetidos às múltiplas ciclagens térmicas apresentam estabilidade térmica suficiente para serem utilizados, por exemplo, em ferramentais de cura de componentes aeronáuticos.
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