Percorrer por autor "Marques, Ana C."
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- Development of Composites of PLA Filled with Different Amounts of Rice Husk Fibers for Fused Deposition ModelingPublication . Pereira, Daniel F.; Branco, A. C.; Cláudio, R.; Marques, Ana C.; Figueiredo-Pina, CélioPolylactic acid (PLA) has been used as a matrix material to produce compo- sites with natural fibers, which present several advantages, being one of them the addition of value to agricultural waste. Thus, this study aims to develop a PLA 3D filament with the incorporation of a waste agriculture product (rice husk (RH)). For that, RH fibers were prepared, and PLA was loaded up to 20% RH. The filaments were obtained by extrusion. Finally, samples were produced by fused deposition modeling (FDM). The fibers and filaments’ density and thermal stability (TGA) were determined, and their chemical structure changes due to alkali treatment were accessed by Fourier Transform Infrared Spectroscopy (FTIR). Printability tests were performed, and printed samples were characterized in terms of density, water absorp- tion, and mechanical behavior (compression, tensile, and flexural tests). The results showed that the alkali treatment changed the chemical structure of RH fibers and TGA showed that the filaments did not degrade significantly until 250ºC. The best printability was achieved with 5% of HR content and was the one that showed the lowest mechanical properties reduction. Overall, the present work showed that RH fibers can be successfully used as a filler in PLA filaments for FDM.
- Development of composites of PLA filled with different amounts of rice husk fibers for fused deposition modelingPublication . Pereira, Daniel F.; Branco, A.C.; Cláudio, Ricardo; Marques, Ana C.; Figueiredo-Pina, C. G.Polylactic acid (PLA) has been used as a matrix material to produce composites with natural fibers, which present several advantages, being one of them the addition of value to agricultural waste. Thus, this study aims to develop a PLA 3D filament with the incorporation of a waste agriculture product (rice husk (RH)). For that, RH fibers were prepared, and PLA was loaded up to 20% RH. The filaments were obtained by extrusion. Finally, samples were produced by fused deposition modeling (FDM). The fibers and filaments’ density and thermal stability (TGA) were determined, and their chemical structure changes due to alkali treatment were accessed by Fourier Transform Infrared Spectroscopy (FTIR). Printability tests were performed, and printed samples were characterized in terms of density, water absorption, and mechanical behavior (compression, tensile, and flexural tests). The results showed that the alkali treatment changed the chemical structure of RH fibers and TGA showed that the filaments did not degrade significantly until 250ºC. The best printability was achieved with 5% of HR content and was the one that showed the lowest mechanical properties reduction. Overall, the present work showed that RH fibers can be successfully used as a filler in PLA filaments for FDM.
- Development of polycarbonate urethane-based materials with controlled diclofenac release for cartilage replacementPublication . Oliveira, Andreia S.; Ferreira, Inês; Branco, Ana C.; Silva, João C.; Costa, Carolina; Nolasco, Pedro; Marques, Ana C.; Silva, Diana; Colaço, Rogério; Figueiredo-Pina, Célio; Serro, Ana P.ydrogels are very promising human cartilage replacement materials since they are able to mimic its structure and properties. Besides, they can be used as platforms for drug delivery to reduce inflammatory postsurgical reactions. Polycarbonate urethane (PCU) has been used in orthopedic applications due to its long-term biocompatibility and bio-durability. In this work, PCU-based hydrogels with the ability to release an anti-inflammatory (diclofenac) were developed, for the first time, for such purpose. The materials were reinforced with different amounts of cellulose acetate (CA, 10%, 15%, and 25% w/w) or carbon nanotubes (CNT, 1% and 2% w/w) in order to improve their mechanical properties. Samples were characterized in terms of compressive and tensile mechanical behavior. It was found that 15% CA and 2% CNT reinforcement led to the best mechanical properties. Thus, these materials were further character- ized in terms of morphology, wettability, and friction coefficient (CoF). Contrarily to CNTs, the addition of CA significantly increased the material's porosity. Both mate- rials became more hydrophilic, and the CoF slightly increased for PCU + 15%CA. The materials were loaded by soaking with diclofenac, and drug release experiments were conducted. PCU, PCU + 15%CA and PCU + 2%CNT presented similar release pro- files, being able to ensure a controlled release of DFN for at least 4 days. Finally, in vitro cytotoxicity tests using human chondrocytes were also performed and con- firmed a high biocompatibility for the three studied materials.
- Suitability of Kahili ginger stem fibres for reinforcement/filler of polymeric matrix compositesPublication . Lourenço, Bruno; Serôdio, Rita M. N.; Ferro, Alberto; Marques, Ana C.; Serro, Ana P.; Galante, Raquel; Garcês, Antonio; Claudio, Ricardo; Figueiredo-Pina, Célio G.Kahili ginger (KG) is one of the world's most invasive species, whose proliferation can be controlled by mechanical thinning. The KG chips produced in that process can be used as reinforcement/filler in polymer matrix composites (PMC), adding value to this waste. The aim of this study is to evaluate the possibility of using fibres obtained from KG stem chips for PMC. The chemical composition, thermal stability, water absorption, hydrophilicity and tensile mechanical properties of the KG fibres were assessed, and the values obtained were compared with those reported in the literature for other natural fibres commonly used in the manufacture of PMC. The results showed that the fibres treated with alkali/silane are thermally stable up to 200 °C, have a contact angle of 70°, a water absorption of 24 %, a modulus of elasticity of 23±3 GPa and a tensile strength of 277±113 MPa. Overall, the results demonstrate the potential of KG as a reinforcement/filler material for PMC.
- Super-strong hydrogel composites reinforced with PBO nanofibers for cartilage replacementPublication . Oliveira, Andreia S.; Silva, João C.; Loureiro, Mónica V.; Marques, Ana C.; Kotov, Nicholas A.; Colaço, Rogério; Serro, Ana PaulaCartilage replacement materials exhibiting a set of demanding properties such as high water content, high mechanical stiffness, low friction, and excellent biocompatibility are quite difficult to achieve. Here, poly(p-phenylene-2,6-benzobisoxazole) (PBO) nanofibers are combined with polyvinyl alcohol (PVA) to form a super-strong structure with a performance that surpasses the vast majority of previously existing hydrogels. PVA–PBO composites with water contents in the 59–76% range exhibit tensile and compressive moduli reaching 20.3 and 4.5 MPa, respectively, and a coefficient of friction below 0.08. Further, they are biocompatible and support the viability of chondrocytes for 1 week, with significant improvements in cell adhesion, proliferation, and differentiation compared to PVA. The new composites can be safely sterilized by steam heat or gamma radiation without compromising their integrity and overall performance. In addition, they show potential to be used as local delivery platforms for anti-inflammatory drugs. These attractive features make PVA–PBO composites highly competitive engineered materials with remarkable potential for use in the design of load-bearing tissues. Complementary work has also revealed that these composites will be interesting alternatives in other industrial fields where high thermal and mechanical resistance are essential requirements, or which can take advantage of the pH responsiveness functionality.