Special polymers have been used in the manufacture of storage structures and pipelines avoiding corrosive processes during ethanol fuel transport/storage. Therefore, this work investigated comparatively the effects of the ethanol on the physical-mechanical properties of poly (ether ether ketone) (PEEK) and polyamide 11 (PA-11) based on ageing tests. The WAXD and DSC results demonstrated slight reductions on the crystallinity degree of the aged PEEK, contrariwise to what happened with PA-11, where Xcincreased after ageing. However, the results of thermal, thermomechanical and mechanical analysis (TGA, DMTA, tensile and micro-IITs) demonstrated that PEEK is stable and no significant changes were observed in its elastic modulus (Ey≈ 3.4 GPa, E’ andEit≈ 3.7 GPa) or glass transition temperature. PA-11, conversely, was sensitive to ethanol fuel and expressive changes of its physical-mechanical properties were verified. For both materials, a reasonable correlation between crystallinity and mechanical properties was established.
Derakene is a vinyl ester resin largely employed as matrix for polymeric based composite systems. In this work, the performance of such polymeric system was evaluated considering the effect of hygrothermal aging. The mechanical and thermal properties were examined for the processed material before and after ageing in water at 60 ºC for a maximum period of 64 days. Both analyses indicated the occurrence of post cure of the system after 16 days due to exposition at 60 ºC in water, which was also confirmed by analyses in samples with post cure treatment. Moreover, it was observed plasticizing of resin after 36 and 64 days of ageing. Micro structural and fracture surface analyses were carried out in order to characterize the samples. The appearance of surface voids was also observed.
Three-dimensional polymeric scaffolds have been widely employed as support in tissue engineering to reconstruct damaged or lost tissue. In this study porous structures were obtained using P(3HB) solution with five concentrations of sieved sodium chloride 50, 60, 70, 80 and 90 wt %, with particles size in the range of 75 - 150, 53 - 75 and 38 - 53 µm. Thermal properties of the samples were investigated by differential scanning calorimetry and thermo gravimetric analysis, while the morphology was observed by scanning electron microscopy. Asymmetric porous structures were formed for salt concentrations of 50, 60 and in some cases 70wt%. Additionally, porosity increased as the salt weight fraction was increased and pore diameter increased as the salt particle size increased. X-Ray diffraction analysis showed that salt concentration and granulometry did not influence the crystalline characteristics of the porous matrices when compared with the dense polymer film obtained by casting of a solution without salt. The scaffolds promote the spontaneous deposition of a calcium phosphate layer, indicating bioactivity.
A aplicação de estruturas tridimensionais bio-reabsorvíveis como suporte temporário na engenharia de tecidos tem crescido nos últimos anos. Neste estudo, estruturas porosas de poli(3-hidroxibutirato) (P(3HB)) foram preparadas pelo método de vazamento e lixiviação de partículas. As amostras foram obtidas pela adição de cloreto de sódio em concentrações de 50, 60, 70, 80 e 90% p/p, a uma solução de P(3HB) em clorofórmio. O tamanho das partículas de sal foi controlado nas faixas de 38-53, 53-75 e 75-150 µm. As propriedades térmicas das matrizes poliméricas foram estudadas via calorimetria diferencial de varredura (DSC) e análise termogravimétrica (TGA). A morfologia das amostras foi observada por microscopia eletrônica de varredura (MEV), onde se constatou a formação de estruturas assimétricas para concentrações de sal de 50, 60 e eventualmente 70%. Os tamanhos dos poros obtidos apresentaram dependência somente com a fração em peso inicial e com o tamanho da partícula do sal empregado. Análises de difração de raios X indicaram que o tipo de sal, a concentração e a granulometria não influenciam as características cristalinas do polímero na estrutura porosa. Pelo teste de bioatividade "in vitro" foi constatada a formação espontânea de uma camada de fosfato de cálcio sobre a superfície das estruturas porosas.
Mechanical properties of epoxy based coating materials suitable for in-situ internal application in gas/oil pipelines were studied. Coatings were applied on carbon steel substrates submitted to two different surface preparation procedures (ST3 and SA2½) and the effect from surface treatment on coating adhesion, impact, hardness and wear was evaluated. It was found that adhesion failure occurs through distinct mechanisms depending on coating material and surface preparation. Wear occurs mostly by abrasive mechanism, although adhesive wear was found to be significant in some cases also depending on material and surface. Microhardness, as expected, was found to be a coating property not unaffected by surface treatment.
Propriedades mecânicas de recobrimentos a base de epóxi para aplicação in situ em dutos de transporte na indústria petrolífera foram avaliadas. Os recobrimentos foram aplicados sobre substratos de aço carbono submetidos a dois diferentes padrões de tratamento superficial (ST3 e SA2½) e avaliou-se a influência do mesmo em propriedades tais como adesão, impacto, dureza e desgaste do material. Observou-se que a falha de adesão ocorre por diferentes mecanismos dependendo do material do recobrimento e da preparação da superfície. Desgaste ocorre basicamente por mecanismo abrasivo embora se tenha observado desgaste adesivo significativo em alguns casos, dependendo do material e do padrão de tratamento da superfície. Resultados de microdureza indicaram, como esperado, ser esta uma propriedade inerente ao material, não sendo afetada pelo padrão de limpeza da superfície